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WO2008030337A2 - Rechauffement dielectrique a frequence radio d'hydrocarbures - Google Patents

Rechauffement dielectrique a frequence radio d'hydrocarbures Download PDF

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Publication number
WO2008030337A2
WO2008030337A2 PCT/US2007/018447 US2007018447W WO2008030337A2 WO 2008030337 A2 WO2008030337 A2 WO 2008030337A2 US 2007018447 W US2007018447 W US 2007018447W WO 2008030337 A2 WO2008030337 A2 WO 2008030337A2
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WIPO (PCT)
Prior art keywords
medium
frequency
temperature
radio frequency
heating
Prior art date
Application number
PCT/US2007/018447
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English (en)
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WO2008030337A3 (fr
Inventor
Dwight Eric Kinzer
Original Assignee
Dwight Eric Kinzer
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Filing date
Publication date
Priority claimed from US10/591,566 external-priority patent/US20070215613A1/en
Application filed by Dwight Eric Kinzer filed Critical Dwight Eric Kinzer
Publication of WO2008030337A2 publication Critical patent/WO2008030337A2/fr
Publication of WO2008030337A3 publication Critical patent/WO2008030337A3/fr

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Classifications

    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B6/00—Heating by electric, magnetic or electromagnetic fields
    • H05B6/46—Dielectric heating
    • H05B6/62—Apparatus for specific applications
    • E—FIXED CONSTRUCTIONS
    • E21—EARTH OR ROCK DRILLING; MINING
    • E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
    • E21B43/16—Enhanced recovery methods for obtaining hydrocarbons
    • E21B43/24—Enhanced recovery methods for obtaining hydrocarbons using heat, e.g. steam injection
    • E21B43/2401—Enhanced recovery methods for obtaining hydrocarbons using heat, e.g. steam injection by means of electricity
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B2214/00—Aspects relating to resistive heating, induction heating and heating using microwaves, covered by groups H05B3/00, H05B6/00
    • H05B2214/03—Heating of hydrocarbons

Definitions

  • This invention relates to hydrocarbon processing and extraction, specifically to heating hydrocarbonaceous formations in situ for more efficient processing and extraction.
  • heavy or viscous oil is often left untapped in a conventionally-produced oil wells, due to the extra cost of extraction.
  • Oil shale is a sedimentary rock, which upon pyrolysis, or distillation, yields a condensable liquid, referred to as a shale oil, and non-condensable gaseous hydrocarbons.
  • the condensable liquid may be refined into products that resemble petroleum products.
  • Oil sand is an errati ⁇ mixture of sand, water, and bitumen, with the bitumen typically being present as a film around water- enveloped sand particles. Though difficult, various types of heat processing can release the bitumen, which is an asphalt-like crude oil that is highly viscous.
  • One proposed electrical in situ approach employs a set of arrays of dipole antennas located in a plastic or other dielectric casing in a formation, such as a tar sand formation.
  • a VHF or UHF power source would energize the antennas and cause radiating fields to be emitted into the deposit.
  • the field intensity drops rapidly as distance from the antennas increases. Consequently, non-uniform heating results in inefficient overheating of portions of formations in order to obtain at least minimum average heating of the bulk of the formations.
  • Another past proposal utilizes in situ electrical induction heating of formations.
  • the process depends on the inherent conduction ability, which is limited even under the best of conditions, of the formations, hi particular, secondary induction heating currents are induced in the formations by forming an underground toroidal induction coil and passing electrical current through the turns of the coil. Drilling vertical and horizontal boreholes forms the underground toroid, and conductors are threaded through the boreholes to form the turns of the toroid.
  • the formations become more resistive, and greater currents are required to provide the desired heating.
  • the above-mentioned techniques are limited by the relatively low thermal and electrical conductivity of the bulk formations of interest. Thus, the inefficiencies resulting from nonuniform heating render existing techniques slow and inefficient.
  • Controlled or uniform temperature heating of a hydrocarbonaceous volume to be recovered is desirable, but current methods cannot achieve this goal. Instead, current methods generally result in non-uniform temperature distributions, which can result in the necessity of inefficient overheating of portions of the formations. Extreme temperatures in localized areas may cause damage to the producing volume such as carbonization, skinning of the paraffin waxes, and arcing between the conductors can occur. Furthermore, vaporization of water creates steam that negatively affects the passage of frequency waves to the substances that require heating.
  • a specific disadvantage of known capacitive RF dielectric heating methods is the potential for thermal runaway or hot spots in a heterogeneous medium since the dielectric losses are often strong functions of temperature.
  • Another disadvantage of capacitive heating is the potential for dielectric breakdown (arcing) if the electric field strengths are too high across the sample. Thicker samples with fewer air gaps allow operation at a lower voltage.
  • Figs 1-4 show an example of a known capacitive RF dielectric heating system.
  • a high voltage RF frequency sinusoidal AC signal is applied to a set of parallel electrodes 20 and 22 on opposite sides of a dielectric medium 24.
  • Medium 24 to be heated is located between electrodes 20 and 22, in an area defined as the product treatment zone.
  • An AC displacement current flows through medium 24 as a result of polar molecules in the medium aligning and rotating in opposite fashion to the applied AC electric field. Direct conduction does not occur. Instead, an effective AC current flows through the capacitor due to polar molecules with effective charges rotating back and forth. Heating occurs because these polar molecules encounter interactions with neighboring molecules, resulting in lattice and frictional losses as they rotate.
  • the resultant electrical equivalent circuit of the device of Fig 1 is therefore a capacitor in parallel with a resistor, as shown in Fig 2A.
  • In-phase component I ⁇ corresponds to the resistive voltage loss.
  • This frequency which is referred to as a "Debye resonance frequency" after the mathematician who modeled it, represents the frequency at which lattice limitations occur.
  • Debye resonance frequency is the frequency at which the maximum energy can be imparted into a medium for a given electric field strength (and therefore the maximum heating).
  • This high frequency limitation is inversely proportional to the complexity of the polar molecule. For example, hydrocarbons with polar side groups or chains have a slower rotation limitation, and thus lower Debye resonance, than simple polar water molecules. These Debye resonance frequencies also shift with temperature as the medium 24 is heated.
  • Figs 2A, 2B, and 2C are equivalent circuit diagrams of the dielectric heating system of Fig 1 for different types of hydrocarbon-bearing formations. Resultant electrical equivalent circuits may be different from the circuit shown in Fig 2A, depending on the medium 24. For example, in a medium 24 such as a hydrocarbonaceous formation with a high moisture and salt content, the electrical circuit only requires a resistor (Fig 2B), because the ohmic properties dominate. For media with low salinity and moisture, however, the resultant electrical circuit is a capacitor in series with a resistor (Fig 2C).
  • FIGs 3 and 4 An example of a conventional RF heating system is shown in Figs 3 and 4 (Prior Art).
  • a high voltage transformer/rectifier combination provides a high-rectified positive voltage (5 k V to 15 kV) to the anode of a standard triode power oscillator tube.
  • a tuned circuit parallel inductor and capacitor tank circuit
  • FIG 4 An example of a conventional RF heating system is shown in Figs 3 and 4 (Prior Art).
  • a tuned circuit parallel inductor and capacitor tank circuit
  • This RF signal generator circuit output then goes to the combined capacitive dielectric and resistive/ohmic heating load through an adapter network consisting of a coupling circuit and a matching system to match the impedance of the load and maximize heating power delivery to the load, as shown in Fig 3.
  • An applicator includes an electrode system that delivers the RF energy to the medium 24 to be heated, as shown in Fig 1.
  • the known system of Figs 1-4 can only operate over a narrow band and only at a fixed frequency, typically as specified by existing ISM (Industrial, Scientific, Medical) bands. Such a narrow operating band does not allow for tuning of the impedance. Any adjustment to the system parameters must be made manually and while the system is not operating. Also, the selected frequency can drift. Therefore, to the extent that the known system provides any control, such control is not precise, robust, real time or automatic.
  • ⁇ _n extraction and processing method of hydrocarbonaceous formations comprises an in situ heating process that utilizes a Debye frequency heating system, comprising an optional fluid carrier medium (for example, water or a saline solution), which can be unaffected, when desired, by the frequencies being presented to the target elements within the formation.
  • a Debye frequency heating system comprising an optional fluid carrier medium (for example, water or a saline solution), which can be unaffected, when desired, by the frequencies being presented to the target elements within the formation.
  • Fig 1 is a schematic diagram of an existing capacitive RF dielectric heating system.
  • Figs 2 A, 2B and 2C are equivalent circuit diagrams of the dielectric heating system of Fig 1 for different types of hydrocarbon-bearing formations.
  • Fig 3 (Prior Art) is a block diagram of the dielectric heating system of Fig 1.
  • Fig 4 is a block diagram showing the high power RF signal generation section of the dielectric heating system of Fig 3 in greater detail.
  • Fig 5 is a block diagram of a capacitive RF dielectric heating system in accordance with the invention.
  • Fig 6 is a flow chart illustrating steps of impedance matching methods for use in the capacitive RF dielectric heating system diagrammed in Fig 5.
  • Fig 7 is a block diagram similar to Fig 5, except showing an alternative embodiment of a capacitive RF dielectric heating system.
  • Fig 8 is a flow chart illustrating steps of impedance matching methods for use in the capacitive RF dielectric heating system diagrammed in Fig 7.
  • Fig 9 is a top plan view of a grid electrode, which may be used in the systems of Figs 5 and 7.
  • Fig 10 is a sectional view taken along line 10-- 10 of Fig 9.
  • Figs 1 IA through 1 IE are block diagrams of five hydrocarbon heating and extraction process flows which benefit from use of a dielectric heating system.
  • Fig 12 shows three frequency generating and monitoring wells with their devices activated at the bottom of a hyrdrocarbonaceous deposit.
  • Fig 13 shows a cavern opening upward in the center to form a larger, cone- shaped main cavern .
  • Fig 14 shows a main cavern expanded to include the adjacent caverns seen in Fig 13.
  • Fig 15 shows the main cavern, which will soon be limited in its outward and upward spread into the formation, and will begin to appear dome-shaped as the formation is exploited.
  • Fig 16 shows a close up of the main cavern, within brackets 16 — 16 from Fig 15, and several process techniques.
  • 170 step set signal generator 30 to an initial frequency or frequencies
  • the Debye frequency heating of the present invention can be utilized either alone or in conjunction with other in situ recovery techniques to maximize efficiency for given applications.
  • Fossil fuel also known as mineral fuel, is used synonymously with other hydrocarbon-containing natural resources such as oil shale, tar sand, oil sand, coal, bitumen, heavy oil, crude petroleum, petroleum distillates, kerogen, oil, and natural gas.
  • Fossil fuel is a general term for buried combustible geologic deposits of organic materials, formed from decayed plants and animals that have been converted to crude oil, coal, natural gas, or heavy oils by exposure to heat and pressure in the earth's crust over hundreds of millions of years.
  • Capacitive dielectric heating differs from lower frequency ohmic heating in that capacitive heating depends on dielectric losses.
  • Ohmic heating on the other hand, relies on direct ohmic conduction losses in a medium and requires the electrodes to contact the medium directly. (In some applications, capacitive and ohmic heating are used together.)
  • Capacitive RF dielectric heating methods offer advantages over other electromagnetic heating methods. For example, such heating methods offer more uniform heating over the sample geometry than higher frequency radiative dielectric heating methods (e.g., microwaves), due to superior or deeper wave penetration into the sample and simple uniform field patterns. In addition, capacitive RF dielectric heating methods operate at frequencies low enough to use standard power grid tubes that are lower cost (for a given power level) and allow for generally much higher power generation levels than microwave tubes.
  • Capacitive RF dielectric heating methods also offer advantages over low frequency ohmic heating. These include the ability to heat a medium, such as medium 24, 124, or 304 shown in Figs 5, 7, or 12-16, that is surrounded by an air or fluid barrier (i.e., the electrodes do not have to contact the medium directly). The performance of capacitive heating is therefore also less dependent on the product making a smooth contact with the electrodes. Capacitive RF dielectric heating methods are not dependent on the presence of DC electrical conductivity and can heat insulators as long as they contain polar dielectric molecules that can partially rotate and create dielectric losses. A typical existing design for a capacitive dielectric heating system is described in "Electric Process Heating: Technologies/Equipment/ Applications", by Orfeuil, M., Columbus: Battelle Press (1987).
  • the present methods and systems provide for improved overall performance and allow for more precise and robust control of the heating processes.
  • specific dielectric properties of hydrocarbons, elements, or chemical compositions within a bitumen deposit or other hydrocarbonaceous formation are determined and/or used in the process, either directly as process control parameters or indirectly as by reference to a model used in the process that includes relationships based on the properties.
  • New ways of using capacitive RF dielectric heating in the various phases of heating hydrocarbon deposits and techniques to separate foreign matter prior to above surface extraction are disclosed. Two approaches are described below.
  • a variable frequency RF waveform is generated.
  • the waveform is output to an amplifier and an impedance matching network to generate an electric field to heat the hydrocarbon bearing matter.
  • the system is controlled to provide optimum heating. Multiple frequency power waveforms can be applied simultaneously.
  • Characterization of dielectric properties vs. frequency and temperature of medium 24, 124, or 304 assists in the design of a capacitive RF dielectric heating system to lower the viscosity of hydrocarbons, separate unwanted elements or compositions within a hydrocarbon bearing deposit, and extract the desirable hydrocarbons, elements, and/or compounds to the surface, by some methods of the present invention.
  • Medium 24, 124, or 304 is hydrocarbonaceous material, which may include one or more of the following: a kind of subterranean hydrocarbon formation, gas hydrates, kerogen, bitumen, oil shales, paraffin, waxes, and other chemical compositions such as sulfur.
  • An electromagnetic/heat transfer mathematical model can be used to predict the dielectric heating characteristics of various hydrocarbons and related formation substances. Such a model may involve 2-D and/or 3-D mathematical modeling programs as well as finite element methodologies to model composite materials. Best results are achieved with a model that integrates both electromagnetic and heat transfer principles.
  • variable components of the tunable RF signal generator circuit and associated matching networks are actively tuned to change frequency, or tuned automatically, or switched with a control system. Therefore, a software control system is also provided to set up the frequency profile.
  • a variable frequency synthesizer or generator and a broadband power amplifier and associated matching systems and electrodes are useful components of such a capacitive dielectric heating system.
  • temperature monitoring of medium 24, 124, or 304 using thermal sensors such as sensors 42, 137a, 137b, and/or 316 or infrared scanners is conducted, the data is fed back into the control system, and the frequency groups from the generator are swept accordingly to track a parameter of interest, such as Debye resonances (explained below) or other dielectric property, or other temperature dependent parameters.
  • a parameter of interest such as Debye resonances (explained below) or other dielectric property, or other temperature dependent parameters.
  • capacitive heating systems operate at frequencies in the Medium Frequency (MF: 300 kHz— 3 MHz) and/or High Frequency (HF: 3 MHz-30 MHz) bands, and sometimes stretch into the lower portions of the Very High Frequency (VHF: 30 MHz-300 MHz) band.
  • the frequency is generally low enough that the assumption can be made that the wavelength of operation is much larger than the dimensions of the hydrocarbonaceous deposit medium 24, 124, or 304 , thus resulting in highly uniform parallel electric field lines of force across the components of medium 24, 124, or 304 and/or fluid carrier medium 26 or 320 targeted for heating.
  • Electrical impedance is a measure of the total opposition that a circuit or a part of a circuit presents to electric current for a given applied electrical voltage, and includes both resistance and reactance.
  • the resistance component arises from collisions of the current-carrying charged particles with the internal structure of a conductor.
  • the reactance component is an additional opposition to the movement of electric charge that arises from the changing electric and magnetic fields in circuits carrying alternating current. With a steady direct current, impedance reduces to resistance.
  • input impedance is defined as the impedance looking into the input of a particular component or components
  • output impedance is defined as the impedance looking back into the output of the component or components
  • the heating load is the combination of medium 24, 124, or 304 (i.e., the hydrocarbonaceous substances, other specific compositions natural to the formation, and /or water), fluid carrier medium 26 or 320 (if used), and exposed formation, e.g., capacitive electrodes 20, 22, 318 and any electrode enclosure that may be present.
  • the actual load impedance is the input impedance looking into the actual load.
  • the impedance of medium 24, 124, or 304 is influenced by its ohmic and dielectric properties, which may be temperature dependent.
  • the actual load impedance typically changes over time during the heating process because the impedance of medium 24, 124, or 304 varies as the temperature changes.
  • the effective adjusted load impedance which is also an input impedance, is the actual load impedance modified by any impedance adjustments.
  • impedance adjustments include the input impedance of a tunable impedance matching network coupled to the load and/or the input impedance of a coupling network coupled to the structure surrounding the load (e.g., the electrodes and/or enclosure, if present).
  • the effective load includes the impedance load of any impedance adjusting structures and the actual load.
  • Other impedance adjustments that may assist in matching the effective adjusted load impedance to the output impedance of the signal generating unit may also be possible.
  • the effective load impedance is the parameter of interest in the present impedance matching approach.
  • the signal-generating unit refers to the component or components that generate the power waveform, amplify it (if necessary), and supply it to the load.
  • the signal -generating unit includes a signal generator, an amplifier that amplifies the signal generator output and conductors, e.g. a coaxial cable, through which the amplified signal generator output is provided to the load.
  • the signal generating unit's impedance that is of interest is its output impedance.
  • the output impedance of the signal generating unit is substantially constant within the operating frequency range and is not controlled. Both the input impedance and the output impedance of the power amplifier, as well as the signal generator out impedance and the conductor characteristic impedance are substantially close to 50 ohms. As a result, output impedance of the signal-generating unit is also substantially close to 50 ohms.
  • matching the effective adjusted load impedance to the output impedance of the signal generating unit reduces to adjusting the effective adjusted load impedance such that it "matches" 50 ohms.
  • a suitable impedance match is achieved where the effective adjusted load impedance can be controlled to be within 25 to 100 ohms, which translates to nearly 90% or more of the power reaching the actual load.
  • Impedance matching is carried out substantially real-time, with control of the process taking place based on measurements made during the process. Impedance matching can be accomplished according to several different methods. These methods may be used individually, but more typically are used in combination to provide different degrees of impedance adjustment in the overall impedance matching algorithm.
  • the frequency of the signal generator may be controlled.
  • the signal generator frequency is automatically changed based on feedback of a measured parameter.
  • the signal generator frequency may be changed based on the actual load temperature and predetermined relationships of frequency vs. temperature.
  • the frequency may be changed to track Debye resonances as described above and/or to maintain an approximate impedance match. Typically, this serves as a relatively coarse control algorithm.
  • aspects of the power waveform supplied to the effective load can be measured, fed back and used to control the frequency.
  • the forward power supplied to the effective load and the reverse power reflected from the effective load can be measured, and used in conjunction with measurements of the actual voltage and current at the load to control the frequency.
  • a tunable matching network can be automatically tuned to adjust the effective load impedance to match the output impedance of the signal generating unit.
  • series inductance is used in the output portion of the impedance matching network to tune out the series capacitive component of the actual load impedance.
  • the series inductance is set by measuring the initial capacitive component, which is determined by measuring the voltage and current at the actual load and determining their phase difference. It is also possible to measure the voltage and current within the matching network and control for a zero phase shift. For more complex models of the load, other models will be necessary.
  • An alternative approach would be to use a shunt inductor to tune out a shunt capacitive load.
  • An antenna or frequency-emitting device 318 and 368 is an electrical device designed to transmit or receive radio waves 315 or, more generally, any electromagnetic waves.
  • an antenna is an arrangement of conductors or electrodes 20 and 22 that generate a radiating electromagnetic field in response to an applied alternating voltage and the associated alternating electric current, or can be placed in an electromagnetic field so that the field will induce an alternating current in the antenna and a voltage between its terminals.
  • An antenna 318 and 368 array is a plurality of active antennas 318 and 368 coupled to a common source or load to produce a directive radiation pattern. By adding additional conducting rods or coils (called elements or electrodes) and varying their length, spacing, and orientation (or changing the direction of the antenna beam), an antenna 318 and 368 with specific desired properties can be created.
  • the antenna 318 and 368 can be constructed of composite materials such as fiberglass, plastic, polyvinyl choloride, ceramic, teflon, metal limaintaes, epoxy, fber, clay-filled phenolics, and/or reinforced epoxy.
  • the antenna 318 and 368 and/or coaxial transimission line 319 can be fabricated with flexible mechanical joints.
  • the antenna(s) 318 and 368 can be located connected to or near production pipe or at another location in hydrocarbon-bearing formation 304.
  • the antenna(s) 318 and 368 can be in a collinear array. There are a number antenna 318 and 368 variations that can be used, not limited to solenoid and helical.
  • Fig 5 One exemplary system suitable for the first approach, in which at least the measured temperature of the hydrocarbonaceous substance(s), specific chemical compositions, and/or hydrocarbons targeted for heating is monitored, is shown in Fig 5.
  • the system of Fig 5 includes a variable RF frequency signal generator 30 with output voltage level control, a broadband linear power amplifier 32, and a tunable impedance- matching network 34 (for fixed or variable frequency operation) to match the power amplifier output impedance to the load impedance of the capacitive load, which includes electrodes 20 and 22 and medium 24, and may or may not contain fluid carrier medium 26 being optionally heated.
  • Fluid carrier medium 26 preferably is generally a liquid such as water, a saline solution, or de-ionized water, but other fluids could be used such as natural gas, nitrogen, carbon dioxide, and flue gas.
  • the system is constructed to provide an alternating RF signal displacement current 36 at an RF frequency in the range of 300 kHz to 300 MHz.
  • This range includes the MF (300 kHz to 3 MHz), HF (3 MHz to 30 MHz), and VHF (30 MHz to 300 MHz) frequencies in the lower regions of the radio frequency (RF) range.
  • MF 300 kHz to 3 MHz
  • HF 3 MHz to 30 MHz
  • VHF (30 MHz to 300 MHz
  • the range spectrum can be expanded to 1 Hz-10 GHz and is not limited to the radio frequency bandwith.
  • variable RF frequency signal generator 30 is a multi-RF frequency signal generator capable of simultaneously generating multiple different frequencies. Although a single frequency signal generator may be used, the multi-frequency signal generator is useful for methods in which frequency-dependent dielectric properties of specific compositions and/or hydrocarbons targeted tor heating are monitored and used in controlling the heating process, such as is explained in the following section.
  • the energy efficiency and/or heating rate are maximized at or near the location in frequency of the "Debye resonance" (defined earlier) of medium 24.
  • dielectric properties other than Debye resonances are tracked and used in controlling capacitive RF dielectric heating, e.g., when Debye resonances are not present or are not pronounced. These other dielectric properties may be dependent upon frequency and/or temperature, similar to Debye resonances, but may vary at different rates and to different extents. Examples of such other dielectric properties are electrical conductivity and electrical permitivity.
  • the RF signal frequency is tuned to the optimal Debye frequency or frequencies of targeted media 24 for heating hydrocarbons and/or chemical compositions that reside in hydrocarbonaceous material. Multiple Debye resonances may occur in a composite material. So, multiple composite frequency groups can be applied to handle the several Debye resonances. Also, the RF signal frequencies can be varied with temperature to track Debye frequency shifts with changes in temperature.
  • the RF frequency or composite signal of several RF frequencies is selected to correlate with the dominant Debye resonance frequency groups of medium 24 that is being heated. These Debye resonances are dependent on the polar molecular makeup of medium 24 and thus are researched for different types of hydrocarbon compounds, and/or specific chemical compositions or elements that reside in hydrocarbonaceous deposits, to appropriately program the heating system.
  • the generation system in this case variable RF frequency signal generator 30, is capable of generating more than one frequency simultaneously.
  • the control system for this heating system is capable of being calibrated for optimal efficiency to the various hydrocarbons or chemical compositions that are targeted for heating.
  • the frequency or composite frequency groups of the RF signal used in the heating system will track with and change with temperature to account for the fact that the Debye resonance frequencies of the polar molecular constituents of the hydrocarbonaceous material or other targeted medium 24 also shift with temperature.
  • the RF signal power level and resulting electric field strength can be adjusted automatically by a computer control system which changes the load current to control heating rates and account for different hydrocarbon geometries and bitumen, oil shale, or heavy oil compositions.
  • the power level is controlled by: (1) measuring the current and field strength across the actual load with voltage and current measurement equipment 35 (Fig 5); and (2) adjusting the voltage (AC field strength), which in turn varies the current, until measurements of the current and field strength indicate that the desired power level has been achieved.
  • computer 38 also controls multi-frequency RF signal synthesizer 30 to change its frequency and to adjust the tunable impedance matching network 34.
  • the computer 38 can also represent a microprocessor.
  • Fig 6 is a flowchart showing a heating process according to the first approach in more detail.
  • signal generator 30 is set to an initial frequency or frequencies.
  • initial frequency or frequencies For expository convenience, it is assumed in this example that a single frequency is set, but the description that follows applies equally to cases where multiple frequencies are set.
  • the set frequency may be selected with reference to a predetermined frequency or frequency range based on a known relationship between frequency and temperature.
  • the set frequency may be selected based on one or more Debye resonances of the medium 24 as described above.
  • step 172 the temperature at medium 24 is measured.
  • step 174 the measured temperature and set frequency are compared to a predetermined relationship of frequency and temperature for medium 24.
  • the relationship may be stored in computer 38, e.g., in the form of a look-up table.
  • step 176 If the comparison between the set frequency and the predetermined frequency indicates that the set frequency must be changed (step 176; YES), the process advances to step 178, the set frequency is automatically changed by control signals sent to signal generator 30, and step 174 is repeated. If no change in the set frequency is required (step 176; NO), the process advances.
  • an automatic impedance matching process 181 follows step 176.
  • automatic impedance matching begins with step 182.
  • step 182 the magnitude and phase of the actual load impedance are measured using voltage and current measurement equipment 35, and the measured values are relayed to computer 38.
  • step 184 the phase angle difference between the measured voltage and current is determined to tune out the reactance component of the impedance.
  • One element of controlling impedance match is, therefore, to tune out the capacitive reactance component of the actual load resulting in zero phase shifts between the voltage and current.
  • step 186 the impedance match between the signal generating unit and the effective load is measured.
  • impedance match can be controlled through measuring the power waveforms supplied to and reflected from the effective load (the "forward and reverse powers") (optional sub-step 188), assuming the system of Fig 5 is configured to include a measurement instrument 156 and directional coupler 150 as shown in Fig 7, which will be discussed later. (Measurement of the forward and reverse powers is described in the following section.)
  • step 190 the effective load impedance is compared to the predetermined impedance of the signal-generating unit. If the impedance match is not sufficient, the process proceeds to step 192. If the impedance match is sufficient, the process proceeds to step 194.
  • step 192 the effective load impedance is adjusted.
  • the effective load impedance is adjusted by automatically tuning tunable impedance matching network 34 based on control signals sent from computer 38 (step 193).
  • step 192 the process returns to step 186.
  • step 194 the measured temperature is compared to a desired final temperature. If the measured temperature equals or exceeds the desired final temperature, the heating process in completed (step 196). Otherwise, heating is continued and the process returns to step 172.
  • Heating hydrocarbons or other targeted elements or specific chemical compositions can be rapidly achieved.
  • the rapid heating capability is due to the same uniform heating advantage described above and the maximum power input to the heated load by the matching of generator frequency or composite of frequencies to the Debye resonance frequency groups of the targeted compositions that reside in hydrocarbon- bearing formations 304, and tracking those Debye resonance frequency groups with temperature.
  • Power control capability of the generator/heating system allows for the ability to set heating rates to optimize heating processes.
  • higher overall energy efficiency is obtained by matching the generator frequency or composite of frequencies of the RF waveform to the Debye resonance frequency groups of the specific compositions that reside in hydrocarbonaceous formations and by tracking those resonances with temperature resulting in a shorter heating time per unit volume for a given energy input.
  • this technology can be set up to target the Debye resonances of those constituents of hydrocarbon for which heating is desired and avoid the Debye resonances of other constituents (e.g., water, sulfur, sand, shale, other hydrocarbonaceous related substances) of which heating is not desired by setting the generator frequency or frequency groups of the RF waveform to target the appropriate Debye resonances and track them with temperature and avoid other Debye resonances.
  • constituents of hydrocarbon e.g., water, sulfur, sand, shale, other hydrocarbonaceous related substances
  • enhanced feedback and automatic control are used to match the effective adjusted load impedance with the output impedance of a signal generating unit that produces an amplified variable frequency RF waveform.
  • the system of Fig 7 is similar to the system of Fig 5, except that the system of Fig 7 provides for direct measurement of the power output from the amplifier, and this result can be used to match the load impedance to the output impedance of the signal generating unit, as is described in further detail below. Specifically, the system of Fig 7 provides for measuring the forward and reflected power, as well as the phase angle difference between the voltage and the current.
  • the temperature of medium 124 during the process is not used as a variable upon which adjustments to the process are made, although it may be monitored such that the process is ended when a desired final temperature is reached.
  • Elements of Fig 7 common to the elements of Fig 5 are designated by the Fig 5 reference numeral plus 100.
  • medium 124 in Fig 7 is the same as medium 24 in Fig 5.
  • Fig 7 shows a variable RF frequency generator 130 connected to a broadband linear power amplifier 132, with amplifier output 133 being fed to a tunable impedance matching network 134.
  • amplifier 132 is a 2 kW linear RF power amplifier with an operating range of 10 kHz to 300 MHz, although a 500 W-100 kW amplifier could be used.
  • a tunable directional coupler 150 Positioned between amplifier 132 and matching network 134 is a tunable directional coupler 150 with a forward power measurement portion 152 and a reverse power measurement portion 154.
  • Tunable directional coupler 150 is directly connected to amplifier 132 and to matching network 134.
  • Forward and reverse power measurement portions 152 and 154 are also each coupled to connection 133 (which can be on a coaxial transmission line) between amplifier 132 and matching network 134 to receive respective lower level outputs proportional to forward and reverse power transmitted through connection 133.
  • These lower level outputs which are at levels suitable for measurement, can be fed to a measurement device 156. If a 25 W sensor is used in each of forward and reverse power measurement portions 152 and 154, the measurement capability for forward and reverse power will be 2.5 kW with a coupling factor of —20 dB.
  • Measurement device 156 allows a voltage standing wave ratio (SWR) to be measured.
  • the voltage SWR is a measure of the impedance match between the signal generating circuitry output impedance and the effective load impedance.
  • matching network 134 can be tuned to produce an impedance adjustment such that the effective adjusted load impedance matches the signal generating circuitry output impedance.
  • a voltage SWR of 1 : 1 indicates a perfect match between the signal generating circuitry output impedance and the effective load impedance, whereas a higher voltage SWR indicates a poorer match. As described above, however, even a voltage SWR of 2:1 translates into nearly 90% of the power reaching the load.
  • Measurement device 156 can also determine the effective load reflection coefficient, which is equal to the square root of the ratio of the reverse (or reflected) power divided by the forward power.
  • measurement device 156 can be an RF broadband dual channel power meter or a voltage standing wave ratio meter.
  • control heating by controlling for a minimum reflected power, e.g., a reflected power of about 10% or less of the forward power.
  • an AC RF power waveform 136 is fed from matching network 134 to the load, which includes electrodes 120 and 122 and a medium 124 to be heated in the product treatment zone between electrodes 120 and 122.
  • the system of Fig 7 includes voltage and current measurement equipment 135, to measure the voltage applied across the capacitive load and current delivered to the capacitive load, which can be used to determine load power and the degree of impedance match.
  • the voltage, current, and optional temperature measurement devices 135 includes inputs from an RF current probe 137a, which is shown as being coupled to the connection between network 134 and electrode 120, and an RF voltage probe 137b, which is shown as being connected (but could also be capacitively coupled) to electrode 120.
  • probes 137a and 137b that are broadband units, and voltage probe 137b that has a 1000:1 divider.
  • a capacitively coupled voltage probe with a divider having a different ratio can also be used.
  • Capacitive reactance in a circuit results when capacitors or resistors are connected in parallel or series, and especially when a capacitor is connected in series to a resistor.
  • the current flowing through an ideal capacitor is —90 degrees out of phase with respect to an applied voltage.
  • the capacitive reactance can be "tuned out” by adjusting tunable network 134. Specifically, inductive elements within an output portion of tunable matching network 134 are tuned to rune out the capacitive component of the load.
  • Measurement equipment 135 includes a computer interface that processes the signals into a format readable by computer 138.
  • the computer interface may be a data acquisition card, and it may be a component of a conventional oscilloscope. If an oscilloscope is used, it can display one or both of the current and voltage signals, or the computer may display these signals.
  • the system of Fig 7 includes feedback control as indicated by the arrows leading to and from computer 138. Based on input signals received from measurement instrument 156, measurement equipment 135, and algorithms processed by computer 138, control signals are generated and sent from computer 138 to frequency generator 130 and matching network 134.
  • the control algorithm executed by the computer may include one or more control parameters based on properties of hydrocarbonaceous medium 24, specific chemical compositions, and/or hydrocarbons in medium 24, or a fluid carrier medium 320 (as will be discussed elsewhere), targeted for heating, as well as the measured load impedance, current, voltage, forward and reverse power, etc.
  • the algorithm may include impedance vs. temperature information for a specific hydrocarbon composition such as butane as a factor affecting the control signal generated to change the frequency and/or to tune the impedance matching network.
  • Fig 8 is a flowchart illustrating steps of capacitive RF heating methods using impedance matching techniques.
  • the signal-generating unit is set to an initial frequency, which, as in the case of step 170 in Fig 6, may be based on a predetermined frequency vs. temperature relationship, and the heating process is initiated.
  • an automatic impedance matching process 208 follows step 200.
  • automatic impedance matching begins with step 210.
  • step 210 the magnitude and phase of the actual load impedance are measured using the voltage and current measurement equipment 135, and the measured values are relayed to the computer 138.
  • step 212 the phase angle difference between the measured voltage and current is determined to tune out the reactance component of the impedance.
  • step 213 the impedance match between the signal generating unit and the effective load is measured.
  • measuring the impedance match includes measuring the forward and reverse powers (sub-step 214), and a voltage SWR is calculated as described above. The calculated voltage SWR is fed back to computer 138.
  • step 220 the effective load impedance is compared to the impedance of the signal-generating unit, which is a constant in this example. If the match is not sufficient, e.g., as determined by evaluating the voltage SWR, the process proceeds to step 222. If the impedance match is sufficient, the process proceeds to step 228.
  • the effective load impedance is adjusted.
  • adjusting the effective load impedance i.e., raising or lowering it, may be accomplished in two ways.
  • the impedance matching network e.g., network 134
  • the frequency at which the RF waveform is applied can be changed (sub-step 226) to cause a change in the effective adjusted load impedance.
  • step 222 involves only tuning the impedance matching network, the process can return directly to step 213.
  • Step 228 is reached following a determination that an acceptable impedance match exists.
  • a monitored temperature is compared to a desired final temperature. If the measured temperature equals or exceeds the desired final temperature, the heating process is completed (step 230). Otherwise, heating is continued (step 229) and the process returns to step 210.
  • the feedback process of steps 210, 220, and 222 continues at a predetermined sampling rate, or for a predetermined number of times, during the heating process.
  • the sampling rate is about 1-5 s.
  • the measured temperature may be used as an added check to assist in monitoring the heating process, as well as for establishing temperature as an additional control parameter used in controlling the process, either directly or with reference to temperature-dependent relationships used by the control algorithm.
  • shielding can be used to isolate various components of the system from each other and the surrounding environment.
  • a resonant cavity 158 can be provided to shield the capacitive load and associated circuitry from the surroundings.
  • Other components may also require shielding. Shielding helps prevent interference. Even though the frequency changes during the heating process, it resides at any one frequency value long enough to require shielding.
  • An alternative approach is to use dithering (varying the frequency very quickly so that it does not dwell and produce sensible radiation) or spread the spectrum to reduce the shielding requirement.
  • a secondary impedance matching device e.g., a capacitive coupling network 159 is connected in series between network 134 and electrode 120. Varying the capacitance of the capacitance coupling network aids in impedance matching.
  • a conventional servo motor (not shown) may be connected to the capacitor-coupling network to change its capacitance.
  • the servo motor may be connected to receive control signals for adjusting the capacitance from computer 138.
  • capacitance-coupling network 159 is used for relatively coarse adjustments of load impedance.
  • a network analyzer may also be used in determining impedance levels. Usually, the network analyzer can only be used when the system is not operating. If so, the system can be momentarily turned off at various stages in a heating cycle to determine the impedance of the capacitive load and the degree of impedance matching at various temperatures.
  • the systems of Figs 5 or 7 can employ gridded heating electrodes on the capacitive load for precise control of heating of medium 24 by computer 38, especially to assist with heating heterogeneous media.
  • At least one of the electrodes for example top electrode 20 (Figs 9 and 10) has a plurality of electrically isolated electrode elements 40, such as infrared thermal sensors or other input devices.
  • Bottom electrode 22 also has a plurality electrically isolated electrode elements 44.
  • each top electrode element 40 is located directly opposite a corresponding bottom electrode element 44 on the other electrode.
  • a plurality of switches 46 under control of the computer 38, are provided to selectively turn the flow of current on and off between opposing pairs of electrode elements 40 and 44.
  • an individual computer-controlled variable resistor (not shown) can be included in the circuit of each electrode pair, connected in parallel with the load, to separately regulate the current flowing between the elements of each pair.
  • These arrangements provide the ability to heat individual areas of a hydrocarbon-bearing formation 304, or of an artificially created cavern reservoir 335 of medium 24, 304 or with fluid carrier medium 26, 320 (as will be discussed elsewhere) at different rates than others. These arrangements also protect against thermal runaway or "hot spots" by switching out different electrode element pairs for moments of time or possibly providing different field strengths to different portions of the formation or stratification.
  • Figs 9 and 10 show a compact arrangement where multiple spaced heat sensors 42 are interspersed between electrode elements 40 of top electrode 20.
  • Thermal sensors 42 acquire data about the temperatures of the targeted chemical compositions that reside in hydrocarbonaceous matter medium 24 at multiple locations. This data is sent as input signal to computer 38.
  • the computer uses the data from each sensor to calculate any needed adjustment to the frequency and power level of the current flowing between pairs of electrode elements located near the sensor.
  • the corresponding output control signals are then applied to RF signal generator 30, network 34, and switches 46.
  • Electrodes 20 and 22 are preferably made of an electrically conductive and non-corrosive material, such as stainless steel or gold that is suitable for use in a subterranean environment. Electrodes 20 and 22 can take a variety of shapes depending on the shape and nature of the hydrocarbon-bearing formation or the artificially created cavern. Although Figs 9 and 10 show a preferred embodiment of the electrodes, other arrangements of electrode elements and sensors could be used with similar results or for special purposes.
  • Tests can be conducted to measure and characterize dielectric properties, including Debye resonances, of various constituents of hydrocarbonaceous matter, as functions of frequency (100 Hz-100 MHz) and temperature (0-500° C).
  • Damaskos Test, Inc Various specially-designed fixtures Dielectric Products Co. 9 mm, 100 Hz-I MHz Sealed High Temperature Semi- Solids LD3T Liquid-Tight Capacitive Dielectric Test Fixture
  • HP 16085B Adapter to mate HP 16453 A to HP 4194A 4-Terminal Impedance Bridge Port (40 MHz)
  • HP 16099A Adapter to mate HPl 6453 A to HP 4194A RF IV Port (100 MHz)
  • Temperature/ Thermotron Computer Controlled Temperature/Humidity Humidity Chamber Chamber -68-+177°C, 10%-98% RH, with LN2 Boost for cooling
  • Each of the capacitive dielectric test fixtures is equipped with a precision micrometer for measuring the thickness of the sample, which is critical in calculating the dielectric properties from the measured impedance.
  • the different test fixtures allow for trading off between impedance measurement range, frequency range, temperature range, sample thickness, and compatibility with hydrocarbonaceous matter.
  • the frequency range has been chosen to cover the typical industrial capacitive heating range (300 KHz to 100 MHz) and lower frequencies (down to 100 Hz) to determine OC or low frequency electrical conductivity. This range also identifies Debye resonance locations of various constituents that comprise hydrocarbonaceous matter, such as very complex hydrocarbon molecular chains.
  • the temperature range of 0° C to 99° C for the fluid carrier medium 26, 320 has been chosen to coincide with the desire to keep the fluid carrier medium 26, 320 from vaporizing or limiting the vaporization where the hydrocarbon formation is being heated.
  • Impedance is measured on the samples (both shunt resistance and capacitance). Then, electric permittivity e', permittivity loss factor ⁇ ", and electrical conductivity ⁇ is calculated based on the material thickness, test fixture calibration factors (Hewlett Packard. 1995. Measuring the Dielectric Constant of Solid Materials-HP 4194A Impedance/Gain-Phase Analyzer. Hewlett Packard Application Note 339-13.) and swept frequency data. The following discussion provides details on the technical background covering the dielectric properties of hydrocarbons including Debye resonances.
  • Modeling and predicting capacitive heating performance [0132.]
  • a mathematical model and computer simulation program can model and predict the capacitive heating performance of hydrocarbonaceous materials based on the characterized dielectric properties.
  • G.d Low Frequency Dielectric Constant of a Medium (f«Debye Resonance).
  • e « > High Frequency Dielectric Constant of a Medium (f»Debye Resonance).
  • Equation (13) is also referred to as the Helmholtz equation, and in cases where the time derivative is zero, it reduces to Poisson's Equation.
  • Equation (13) reduces to the following:
  • Equations (8), (9), (12), (14) and (15) form the basis for an electromagnetic dielectric heating model which can be applied to a composite dielectric model, to model a hydrocarbonaceous substance having several subconstituents.
  • the various chemical compositions that reside in hydrocarbonaceous matter may have optimum Debye resonances or frequencies where capacitive RJF dielectric heating will be the most efficient.
  • the capacitive RP dielectric heating system can be set to target those optimum frequencies. These possible Debye resonances in hydrocarbons will have particular temperature dependencies.
  • the capacitive RF dielectric heating system will be designed to track those temperature dependencies during heating as the temperature rises.
  • the targeted chemical compositions that reside in the hydrocarbonaceous matter may have other optimum frequencies that are not necessarily Debye resonances but are still proven to be important frequencies for achieving various desired benefits in either the hydrocarbons or surrounding compositions of the hydrocarbonaceous formation.
  • the capacitive RF dielectric heating system will be capable of targeting those frequencies and tracking any of their temperature dependencies.
  • Target hydrocarbons or certain compositions within the formation may also have Debye resonances or other non-Debye optimum frequencies that are proven to be especially effective in achieving selective heating of the targeted product.
  • the capacitive RF dielectric heating system will be capable of targeting those optimum frequencies and tracking them with temperature to achieve selective control of the heat rate of the targeted composition.
  • the hydrocarbonaceous formation is exposed to a cavern containing a fluid carrier medium, which is made "invisible”, or transparent, to the applied RF electric fields, so that the fluid carrier medium does not reach its boiling point. Accordingly, the fluid carrier medium and the corresponding capacitive RF dielectric heating system is designed for such performance and compatibility.
  • the capacitive RF dielectric heating system will be designed to target the Debye resonances of various chemical compositions that reside in hydrocarbonaceous formations, either simultaneously or in a time-multiplexed manner that approximates simultaneous heating behavior.
  • the frequency and heating profile would be designed to allow for the heating of the formation or specific chemical compositions, and supplementary transfer of heat to the fluid carrier medium with minimal or controlled vaporization.
  • compositions that reside in hydrocarbonaceous matter may have similar dielectric properties, such as similar Debye resonances, and/or dielectric loss factors, thus allowing for more uniform heating.
  • Fig 1 IA shows a flow diagram for a process of capacitive RF dielectric heating of a fossil fuel hydrocarbon-bearing formation, where the device can be preferentially or selectively tuned to heat specific compositions such as hydrocarbons by targeting at least one Debye resonance for at least one chemical composition.
  • Fig HB is a flow diagram showing a process for capacitive RF dielectric heating of hydrocarbon-bearing formations within a subterranean environment, where specific hydrocarbon molecules within the hydrocarbon-bearing formation can be heated with greater intensity than other constituents, such as sand, sulfur, or fluid carrier medium (as will be discussed in detail elsewhere).
  • the device may be tuned to preferentially or selectively heat a fluid carrier medium, which can be a liquid solution, by targeting its Debye resonances instead.
  • a fluid carrier medium which can be a liquid solution, by targeting its Debye resonances instead.
  • the creation of a cavern or fracture filled with a fluid carrier medium allows for heating of hydrocarbons as it comes into contact with the fluid carrier medium.
  • a naturally occurring substance such as a fossil fuel hydrocarbon, sandstone, or other organic or inorganic substances natural to a fossil fuel hydrocarbon- bearing formation can also be used as a carrier medium.
  • a artificially created cavern does not have to used as a naturally occurring fracture(s) or layer, and/or artificially created fracture can also be utilized.
  • Fig 11C is a flow diagram summarizing a process for capacitive RF dielectric heating of hydrocarbon-bearing formations within a subterranean environment, where specific chemical compositions are targeted with Debye frequencies to be heated with greater intensity than other constituents.
  • hydraulic pressure of the fluid carrier medium is used against the hydrocarbon-bearing formation.
  • the fluid carrier medium can be treated with Debye frequency heating tuned for targeted compositions.
  • Fig 1 ID shows a flow diagram for a process for capacitive RF dielectric heating of hydrocarbon-bearing formations within a subterranean environment, where specific hydrocarbon molecules or other chemical compositions within a hydrocarbonaceous medium can be heated with greater intensity than other constituents, such as sand, sulfur, or a fluid carrier medium.
  • a cavern as will be shown elsewhere
  • a process can be instituted to separate the desired substances that are lighter than the fluid carrier medium.
  • These desired hydrocarbons will typically be heated as they are tuned to the RF, and they will typically rise to the surface of the subterranean carrier-medium reservoir.
  • the undesirable foreign matter that is heavier than the desirable hydrocarbons and fluid carrier medium will settle to the bottom of the reservoir. The foreign matter will typically remain relatively cool because it is tuned to be invisible to the RF.
  • Fig 1 IE is a flow chart summarizing a process involving Debye frequency heating of individual stratifications that rise to the surface of the fluid carrier medium. Once above the fluid carrier medium, these stratifications can be rapidly heated to several hundred degrees Celsius to create a process that further stratifies the various hydrocarbon chains by density prior to withdrawal to the surface.
  • Fig 12 shows a hydrocarbonaceous formation (medium 304) between an overburden 302 and bedrock or soil 306.
  • Three wells 301 are shown, in this example, and their Debye frequency heating systems have recently been activated.
  • existing and future frequency-emitting devices 318 are shown as hexagons.
  • the frequency(s) being transmitted are represented by radio waves 315, which spread through a fluid carrier medium 320, in what will become a main cavern 335 (center) and satellite caverns 355, to a hydrocarbon-bearing formation, medium 304.
  • hydrocarbonaceous materials 330 and/or other materials are being pumped upward to the surface (depicted by arrows pointing upward).
  • Fluid carrier medium 320 drawn from a storage reservoir 308, is being injected downward into caverns 335 and 355 (represented by downward arrows).
  • Derricks 310 are used for boring holes, and for placing well casings and piping, (contents of cavern such as melted bitumen tar sands or blasted oil shale as the cavern is being formed during the cavern's initial creation is represented by 328.)
  • Frequency emitting devices 318 with heater grid electrodes (such as electrodes 20 and 22, not shown) and process sensing devices (such as heat sensors 42, not shown) along with other necessary equipment, can be raised and lowered through the boreholes with derricks 310.
  • reservoirs 332 of fluid carrier medium 304 with or without other material begin to form and increase in volume and/or pressure. As will be discussed later, some reservoirs 332 will become main reservoirs 338.
  • Medium 304 that is being heated is shown in Fig 12 as medium being heat- treated 334 or 340, and it is preferably targeted to be near the perimeter of caverns 335 or 355.
  • the magnitude (horizontal and/or vertical depth of medium 304, or distance from frequency emitting devices 318) of medium being treated 334 can vary, depending on the characteristics and properties of the formation and the desired hydrocarbonaceous materials.
  • the well at the far right in Fig 12 is in its very early stages of heat-treating medium 304 (as depicted by medium being heat-treated 334), and the middle and left-most wells are further along in the processing of the hydrocarbonaceous formation (as shown by medium being heat-treated 340).
  • Medium being heat-treated 334 and 340 can be similar in conformation, or they may be different as a result of being at different stages of processing and extraction.
  • Process monitoring devices 316 such as voltage, current, temperature, and infrared thermal sensors or other devices, are shown as a herringbone pattern along the length of the well casings. These monitoring devices 316 perform a number of functions, including, but not limited to, the following:
  • Frequency-emitting devices 318 receive power via transmission cable 319.
  • Data cable 317 conveys sensory information from monitoring devices 316 to computer 38 or 138.
  • each borehole begins providing Debye frequency heating to rapidly raise the temperature near the bottom of the hydrocarbonaceous formation.
  • a typical arrangement has a flexible coaxial transmission cable 319 to power frequency emitting devices 318 (with electrodes 20 and 22, not shown). Sensors 316 are inserted into one or more vertical or horizontal boreholes in the area to be heated. Above- ground RF generators supply energy through coaxial transmission cable(s) 319 to electromagnetically-coupled down-hole electrodes 20 and 22, which are preferably part of frequency-emitting devices 318. Sub-surface material between electrodes 20 and 22 rises in temperature as it absorbs electromagnetic energy. When properly configured, the system can provide spatially-controlled heating patterns by adjusting the operating frequency, electrical phasing of currents of electrodes 20 and 22, and electrode size and location.
  • Fluid carrier medium 320 is preferably water, but it can be virtually any fluid, such as, but not limited to, de-ionized water, a saline water solution, or liquid carbon dioxide, for example. Fluid carrier medium 320 is pumped into one or more caverns 335 and 355, to increase reservoir level and/or pressure, and/or to serve as a coolant to prevent fluid carrier medium 320 within reservoirs 332 from reaching its boiling point. In some cases, the carrier medium can be removed from reservoirs 332 to relieve pressure.
  • this process can require more fluid carrier medium 320, depending largely on the water content of the formation and the amount of water that the formation can contribute to the process, than current methods that require steam and high energy inputs for both subterranean extraction and subsequent above-ground washing.
  • the amount of fluid carrier medium 320 and energy required is significantly less than current methods.
  • fluid carrier medium 320 can be recovered from the bottom of cavern 335 and 355 to reduce or eliminate the energy requirements of pumping into the cavern. This process can continue after mining is completed, as a cost effective method of maintaining pressure, when desired, on fluid carrier medium 320 in the cavern and subsequent natural gas reserve pressures.
  • Fig 13 shows an example of a main cavern 335 that has been formed by the three developing caverns 335 and 355 from Fig 12 converging together as they are expanded during the process.
  • Cavern 335 one cavern formed from the three in Fig 12
  • Reservoirs 332 from Fig 12 have also conjoined to form main reservoir 338.
  • the cone-shaped cavern is desirable for several reasons, such as the following:
  • a cone-shaped cavern encourages heated hydrocarbonaceous matter to propagate towards the center of cavern 335. As the hydrocarbonaceous formation viscosity decreases near main reservoir 338, it will propagate from medium 304 to fluid carrier medium 320 in reservoir 338. For example, as heated tar sand makes contact with fluid carrier medium 320, the bitumen will float on fluid carrier medium 320 while the sand and other debris will sink to the bottom of reservoir 338 as sediment 344. The heated bitumen and hydrocarbons can be brought to the surface after rising to the surface of fluid carrier medium 320;
  • a cone-shaped cavern provides maximum surface area of fluid carrier medium 320 that is exposed to medium 304.
  • a cone-shaped cavern allows for effective placement of separated foreign matter as the cavern opens outwardly at the base bottom of the deposit and up from the center, thus creating an environment that settles the sediment towards the center of the cavern floor.
  • Pyrolysis is the chemical decomposition of organic materials by heating in the absence of or with very little oxygen or any other reagents, except possibly steam. Pyrolysis and/or chemical reaction can include cracking of long -chain hydrocarbons into shorter-chain hydrocarbons.
  • main cavern 335 has now been sufficiently opened and shaped so it can be filled with fluid carrier medium 320 that conducts the frequencies to medium 304.
  • Reservoir 338 with fluid carrier medium 320 and/or other liquids functions to settle out foreign matter as sediment 344 onto the cavern floor. It should be noted that fluids such as saline waters can be conductive for hundreds of feet.
  • a layer 340 of medium being treated 334 is typically between the bulk of the hydrocarbon-bearing formation and the cavern fluid carrier medium 320. Typically, the cavern walls and roof are being heated.
  • the melted bitumen or released oils and hydrocarbons are expected to rise to the surface of reservoir 338 either as a layer 342 against the cavern roof or as bubbles near the surface of reservoir 338 (not labeled).
  • the foreign matter compositions that do not contain sufficient hydrocarbons or that have densities greater than fluid carrier medium 320 is settled as sediment 344 onto the floor of the cavern.
  • a stratified layer 356 of hydrocarbonaceous particulates begins to form, creating an in-situ distillation chamber.
  • the melted bitumen, oils, and hydrocarbons that float to the surface of fluid carrier medium 320 are shown as stratified layer 346 in Fig 13.
  • Stratified layer 346 is extracted with piping 350. Natural gases form stratified layer 348, and they collect at the top of cavern 335.
  • Stratified layer 348 is extracted with piping 352.
  • main cavern 335 has expanded to include caverns 355 from Fig 13.
  • the process of opening up and activating more wells (at far right and left in Fig 14) to expand cavern 335 continues.
  • the center of cavern 335 has risen and widened, and now has a dome cap 364.
  • Pressure differentials are forming within cavern 335 due to the increasing depths of reservoir 338.
  • the bed of sediment 344 is increasing in depth.
  • Figs 15 and 16 depict an advanced phase of many of the techniques presented in this invention. Cavern 335 in Fig 15 and in the close-up view of Fig 16 will soon be limited on outward spread into the formation and has expanded upwards near the top of the hydrocarbon-bearing formation, medium 304. By now, the cone shape of the cavern from Fig 13 has become a dome shape, for full exploitation of the deposit.
  • a device 368 at the base of the well casing (which has been incrementally raised above the encroaching mound of sediment 344) is a high-powered frequency- generating device and an automatic impedance match-monitoring device. If the characteristics of fluid carrier medium 320 and/or reservoir 338 allow for migration of frequencies through long distances, then a centrally-located high-energy generating and monitoring device, such as device 368, is preferred, rather than a grid of wells and devices as previously described in Figs 12 and 13.
  • a process 370 recovers and recycles a layer of fluid carrier medium 320, which is generally a warmed layer of fluid carrier medium 320 immediately below stratified layer 356. If necessary, Debye frequency heating can be placed around or in the pipe of process 370 to rapidly heat medium 304 and fluid carrier medium 320 as a slurry process and/or to saturate reservoir 338 with RF heating frequencies to aid in the mining process. This same process 370 can also be used above ground to heat medium 304 and/or fluid carrier medium 320 during pipeline transport of medium and/or carrier medium.
  • Optional remote controlled underwater vessels 372 and 374 are tethered above ground and piped down into cavern 335. Possible uses for these devices include the following: (a) As a method of delivering high-powered Debye frequency heating to a specific area(s) of the hydrocarbon bearing deposit;
  • Process 376 can recover a stratified layer or layers 356, 358, 360, and/or 362 of melted bitumen, oil, or hydrocarbons and transfer one or more of these stratified layers deep into reservoir 338. While the contents are being transported downward in the pipe, Debye frequency heating rapidly heats the contents of the pipe as slurry 377. Process 376 has the potential to produce crude fractionations of hydrocarbons from heated hydrocarbon substances by rapidly heating the hydrocarbons in a slurry fashion to the necessary temperature and then releasing them under the tremendous hydrostatic pressure created by deep fluids (over 30 meters).
  • additives can be injected by pressure into an in-line mixer built into the piping for process 376. More than one fraction can also be blended together, with additives, and Debye frequency heated as previously described, then released under pressure to create more complex hydrocarbon chains.
  • fluid carrier medium 320 for cavern(s) 335 and/or 355 that is essentially transparent to the RF energy over all or a portion of the 300 KHz— 300 MHz normal operating range, or of the electromagnetic spectrum operating range of 1 KHz - 10 GHz, so that heating of the hydrocarbons or other targeted chemical compositions can be accomplished without boiling fluid carrier medium 320.
  • the product to be heated can be surrounded with or exposed to a non- conductive dielectric coupling fluid carrier medium 320 (e.g., de-ionized water) that itself will not be heated (Debye resonance at much higher frequency) but will increase the dielectric constant of the gaps between the electrodes and the medium to be heated thus lowering the gap impedance and improving energy transfer to the medium.
  • a non- conductive dielectric coupling fluid carrier medium 320 e.g., de-ionized water
  • Pre-heated fluid carrier medium 320 may be at a temperature of 0-99 0 C, in the case of water, or, in general, at a temperature range that is below the boiling point of the medium.
  • the capacitive RF dielectric heating system will have power control and voltage/electric field level control capabilities as well as potentially contain a gridded electrode arrangement (see Figs 9 and 10) to provide precise control of the field strength vs. time and position in medium 304 or fluid carrier medium 320.
  • a gridded electrode system can be used with an infrared scanner to monitor the entire body of a hydrocarbon- bearing formation (medium 304) and/or fluid carrier medium 320 being heated.
  • an infrared scanner to monitor the entire body of a hydrocarbon- bearing formation (medium 304) and/or fluid carrier medium 320 being heated.
  • specific compositions that reside in the hydrocarbonaceous substance such as hydrocarbons and/or other constituents can be independently heated by adjusting local field strengths or by switching some portions of the grid off in different duty cycles to prevent hot spots.
  • Debye frequency heating allows for individual processing of separate stratifications, with real time monitoring and frequency adjustments.
  • Debye frequency heating can be used for in-situ distillation, pyrolysis, and/or chemical reactions.
  • this design requires minimal overall water usage or sediment removal compared to conventional methods.
  • Another advantage is that maximum cavern pressure can be maintained with minimal input of water or other liquids or gases to create and maintain the necessary pressures.
  • the described ⁇ rocess(s) will require significantly less energy. The alleviation of vaporizing the water in a hydrocarbon-bearing formation in itself will greatly decrease the energy requirements. Equally important, and perhaps even more so, significant amounts of green house gases and other by-products are left in its original deposit.
  • Fossil fuel related hydrocarbons 304 such as oil shale, tar sand, oil sand, coal, bitumen, heavy oil, crude petroleum, petroleum distillates and/ or kerogen can be heated by maintaining them in an alternating current electrical field provided by a radio frequency signal at a radio frequency that matches a Debye resonance frequency or frequencies of one or more components, or chemical compositions of the said energy related hydrocarbons 304.
  • a radio frequency signal is automatically adjusted to track changes in the Debye resonance frequency, which shifts in frequency as the temperature rises.

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Abstract

La présente invention concerne un milieu (24 et 124) constitué d'hydrocarbures de combustible fossile (304) qui est réchauffé en maintenant au moins une portion ou une zone du milieu (334) dans un champ électrique de courant alternatif (36 et 136) fourni par un signal de fréquence radio à une fréquence radio qui correspond à une fréquence de résonance ou à des fréquences d'un ou de plusieurs composants du milieu (334). Au fur et à mesure que le milieu (334) ou qu'au moins un composant individuel du milieu (334) augmente en température, la fréquence du signal de fréquence radio est automatiquement réglée pour faire le suivi des changements de fréquence de résonance, qui change au fur et à mesure que la température s'élève. Les portions, zones et/ou compositions chimiques individuelles du milieu (334) peuvent être chauffées par le biais d'électrodes de grille (22, 22, 120, 124), à différentes fréquences afin d'assurer des élévations uniformes de température ou pour parvenir au motif spécifique de réchauffement souhaité.
PCT/US2007/018447 2005-02-24 2007-08-20 Rechauffement dielectrique a frequence radio d'hydrocarbures WO2008030337A2 (fr)

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US10/591,566 US20070215613A1 (en) 2004-03-15 2005-02-24 Extracting And Processing Hydrocarbon-Bearing Formations
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WO2012003827A3 (fr) * 2009-12-16 2012-08-02 Dako Denmark A/S Système de chauffage par micro-ondes interplaque non modal et procédé de chauffage
WO2012138608A1 (fr) * 2011-04-04 2012-10-11 Harris Corporation Traitement d'hydrocarbures utilisant des ondes électromagnétiques radiofréquences
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