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WO1999009435A1 - Procede de prediction de cibles de guide d'ondes continues et discontinues dans lequel on utilise les caracteristiques de signature sismique entre les puits - Google Patents

Procede de prediction de cibles de guide d'ondes continues et discontinues dans lequel on utilise les caracteristiques de signature sismique entre les puits Download PDF

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Publication number
WO1999009435A1
WO1999009435A1 PCT/US1998/015030 US9815030W WO9909435A1 WO 1999009435 A1 WO1999009435 A1 WO 1999009435A1 US 9815030 W US9815030 W US 9815030W WO 9909435 A1 WO9909435 A1 WO 9909435A1
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WIPO (PCT)
Prior art keywords
seismic
waveguide
wave
waves
source
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Application number
PCT/US1998/015030
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English (en)
Inventor
Jorge Octavio Parra
Original Assignee
Gas Research Institute
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from US09/034,530 external-priority patent/US6147929A/en
Application filed by Gas Research Institute filed Critical Gas Research Institute
Priority to AU84143/98A priority Critical patent/AU8414398A/en
Publication of WO1999009435A1 publication Critical patent/WO1999009435A1/fr

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
    • G01V1/00—Seismology; Seismic or acoustic prospecting or detecting
    • G01V1/40—Seismology; Seismic or acoustic prospecting or detecting specially adapted for well-logging
    • G01V1/42—Seismology; Seismic or acoustic prospecting or detecting specially adapted for well-logging using generators in one well and receivers elsewhere or vice versa

Definitions

  • This invention relates to a method applied to reservoir geophysics for delineation of the reservoir architecture of oil or gas fields and for mapping the continuity of producing horizons as well as correlating lithology and stratigraphy between wells.
  • the architecture of a reservoir generally includes structures of flow units, ceiling surfaces and boundary surfaces that result from deposition and digenesis.
  • this invention provides a method for detecting the presence of continuous and discontinuous low- velocity inclusions in subterranean geological formations by analyzing seismic signatures recorded between two or more wells or boreholes, and determining the distance of a discontinuity with respect to the position of a receiver borehole.
  • U.S. Patent 5,144,590 teaches a method for determining the continuity of subsurface formations between well boreholes in which seismic energy is sent from a seismic source in one of the wells at various selected fixed depths and detected by a number of sensing geophones deployed at selected fixed depths in one or more adjacent wells. A frequency domain decomposition process is then performed on the data in order to determine if any of the formations located between the wells function as waveguides for seismic energy within the frequencies of interest. Those formations exhibiting waveguide properties are indicated as continuous between the wells.
  • U.S. Patent 5,005,159 teaches a method of determining the continuity of a lithographic layer located between two vertical boreholes in which a seismic source is lowered into the first borehole while simultaneously a receiver pair, preferably a pair of "vertical" geophones spaced apart by about two feet, are lowered into a second borehole to develop a "difference signal".
  • the recording of high amplitude signals within a layer is an indication of a continuous, low velocity layer.
  • the middle of a layer can also be discovered using a single vertical receiver and finding the place of phase reversal. See also U.S. Patent 4,783,771, U.S. Patent 4,751,688, U.S. Patent 5,197,038, U.S. Patent 5,253,217, U.S.
  • Patent 5,260.911 and U.S. Patent 5,200,928, all of which relate to methods of seismic surveying for defining subterranean formations. See also U.S. Patent 5,481,501 which teaches a method for simulating crosswell seismic data between first and second spaced apart wells and U.S. Patent 5,648,937 which teaches a method and apparatus for adjusting the results of a seismic survey according to well log data obtained from wells within a survey region.
  • a method for detecting a presence of a continuous or discontinuous waveguide in a subterranean geological formation in which at least one seismic signal characteristic of a waveguide target corresponding to a seismic wave receiver borehole is determined.
  • a seismic wave signal is then generated in a source borehole disposed at a distance from the receiver borehole.
  • the seismic wave signal is detected at the receiver borehole and analyzed for a presence of said at least one seismic signal characteristic.
  • the presence of said at least one seismic signal characteristic is indicative of a continuous waveguide disposed between the source borehole and the receiver borehole.
  • the interwell logging method of this invention utilizes the different events characteristic observed in the full waveform seismic signatures for predicting if a low- velocity inclusion, or waveguide, is continuous between wells.
  • Such events can be body waves (direct waves and head waves), interface waves, reflections, leaky modes and normal modes (pseudo- Rayleigh-waves and pseudo-Love- waves).
  • a single event or a combination of these events can constitute a seismic signature that can be used to identify the presence of the inclusion geometry and its physical properties.
  • the analysis of a signature characteristic can predict if the inclusion is continuous or discontinuous between wells.
  • Fig. 1 is a schematic diagram showing a waveguide geometry for the computation of dispersion and attenuation curves as well as synthetic seismograms;
  • Figs. 2(a)-2(f) are pressure synthetic seismograms for sandstone waveguides illustrating the effect of velocity contrast and well separation;
  • Fig. 3 is a diagram showing a P-head wave group velocity contour in the range of 3550-3360 m s;
  • Figs.4(a) and 4(b) are diagrams showing the effect of seismic source placement on leaky mode propagation
  • Figs. 5(a)-5(d) are pressure synthetic seismograms for shale waveguides illustrating the effect of velocity contrast and well separation;
  • Fig. 6 is a diagram showing phase velocity and group velocity curves for the waveguide geometry shown in Fig. 1 ;
  • Fig. 7 is a diagram showing the horizontal component synthetic seismogram produced using an SH-wave source placed in the center of the waveguide shown in Fig. 1, the seismogram showing the signature characteristic of a continuous inclusion;
  • Fig. 8 is a diagram showing seismic responses of a pinch out semi-infinite inclusion for an SH-wave source located at the center of an inclusion and vertical array of detectors intercepting the inclusion at 40 m (meters) and 20 m from the tip of the inclusion as well as the seismic response for an array of detectors located at 10 m outside of the geometry, shown in the last twelve traces; and
  • Fig. 9 shows the seismic response of a pinch out semi-infinite inclusion for an SH-wave source located at the center of the inclusion and a vertical array of detectors intercepting the inclusion at 10 m from the round head of the inclusion.
  • This invention is a method for predicting continuous and discontinuous waveguide targets using interwell seismic signature characteristics.
  • the method of this invention is applied to reservoir geophysics to delineate the reservoir architecture of oil or gas fields and to map the continuity of producing horizons as well as to correlate lithology and stratigraphy between wells.
  • the invention provides a means for detecting the presence of continuous and discontinuous low-velocity inclusions, or waveguides, in subterranean geological formations by analyzing seismic signatures recorded between wells and determining the distance of a discontinuity with respect to the position of the receiver borehole.
  • the method of this invention comprises the steps of determining an appropriate seismic source and an appropriate seismic wave detector suitable for conducting a continuity logging survey based upon well log information and well lithological information for a waveguide target well and determining a seismic characteristic, or seismic signature, for a waveguide of the waveguide target well.
  • This includes well log information comprising low- velocity zones from P-wave and S-wave velocity logs, the thickness of each layer of a geological formation around the waveguide target well, and preferably calculation of at least one dispersion curve and at least one attenuation curve for the waveguide target well.
  • the appropriate seismic source is inserted into a source well or borehole located at a distance from the waveguide target well or receiver borehole and seismic waves are generated using the seismic source.
  • Seismic waves propagated through the subterranean geological formation disposed between the source well and the waveguide target well are detected using at least one seismic detector disposed into the waveguide target well.
  • the seismic waves are then analyzed for the presence of the previously determined seismic characteristic.
  • the presence of at least one seismic characteristic at the waveguide target well is indicative of the presence of a continuous waveguide between the source well and the waveguide target well.
  • Fig. 1 shows a typical source and detector array configuration suitable for use in accordance with the method of this invention.
  • the seismic waves are recorded by a hydrophone array or a three-component detector array.
  • the source borehole and the receiver borehole intercept the waveguide or low-velocity inclusion and the seismic source generates P-waves and S-waves.
  • continuity of the inclusion can be determined by analyzing seismic traces containing head waves, direct waves and leaky modes for waveguides having P-wave velocities greater than the S-wave velocity of the host medium and very low shear wave velocity contrast between the waveguide and the host medium.
  • the resulting signature formed by these seismic events may then be compared to known or experimentally determined formation signatures.
  • the resulting signature formed by these seismic events may correspond to a sandstone waveguide surrounded by shale host medium.
  • the seismic traces contain head waves, direct waves, and normal modes.
  • This signature may correspond to a shale waveguide surrounded by a sandstone host medium.
  • the pressure seismogram shows direct P-wave events which propagate in a waveguide with a P-wave velocity of 1627 m/s (meters/second).
  • the direct P-wave events arrive at the detector after 123 ms and they are followed by reflection events.
  • the full waveforms are dominated by modal wavetrains arriving at 139 ms (milliseconds), which travel with a group velocity of about 168 ms with a velocity of 1190 m/s. These wavetrains are normal modes trapped in the sandstone waveguide.
  • Fig. 2(a) the pressure seismogram shows direct P-wave events which propagate in a waveguide with a P-wave velocity of 1627 m/s (meters/second).
  • the direct P-wave events arrive at the detector after 123 ms and they are followed by reflection events.
  • the full waveforms are dominated by modal wavetrains arriving at 139 ms (milliseconds), which travel with a group velocity of about 168
  • the full waveforms are dominated by normal modes and some leaky modes, that is trailing energy that appears behind the head waves and direct P-waves, which exhibit different signature characteristics from those signals observed for greater velocity contrasts.
  • the leaky modes together with head waves can be used to predict the presence of a waveguide in crosswell data recorded at large well separations.
  • P-head waves and leaky modes form a signature characteristic which represents a sandstone waveguide surrounded by a shale host medium.
  • Fig. 3 shows phase velocity and group velocity curves for leaky modes in a low-velocity layer having P-wave and S-wave velocity ratios of 1.35 and 1.08, respectively.
  • phase velocity contours of leaky modes and P-head waves are superimposed on the theoretical curves. P-head wave contours are observed between 3550-3310 m/s.
  • the phase velocity of mode 1 (or the fundamental leaky mode) has an initial value equal to the P-wave velocity of the host medium (about 3550 m/s). Note that the phase velocity of the fundamental (first) mode decreases as a function of increasing frequency toward the P-wave velocity of the waveguide (2627 m/s).
  • the higher order modes 2, 3 and 4 exhibit cutoff frequencies of 520 Hz, 920 Hz, and 1450 Hz, respectively. Seismic responses were selected for a source and detector placed at 0.5 m and 1 m, respectively, below the upper layer interface.
  • the time-frequency analysis indicates the presence of the first (mode 1) and second leaky (mode 2) modes, as well as the P-head wave.
  • Fig. 3 shows the P-head wave group velocity contour in the range of 3550-3310 m/s.
  • This analysis supports the interpretation that the seismic waves travelling behind the head waves are indeed leaky modes.
  • Dispersion curves of leaky modes constructed using time-frequency plots of selected traces, can be used to verify that the wavetrains following the P-head waves are indeed leaky modes.
  • the head wave and the leaky mode form a seismic signature characteristic that can be used to predict the continuity of waveguide targets that do not support normal modes, that is, very low S-wave velocity contrast between the host medium and the waveguide.
  • Two common-source seismograms with source depths of 974 feet and 940 feet were selected from crosswell data recorded in a detector well at 105 m from a source well.
  • the common-source seismogram at 974 feet was selected because the source was placed inside a 4-m thick sand waveguide in a fluvial environment previously characterized by Turpening, W.R. et al., "Detection of Reservoir Continuity Using Crosswell Seismic Data-A Gypsy Pilot Study," S.P.E. 24711, 1992 and Parra, et al., cited hereinabove.
  • the waveguide is formed by a low velocity sand surrounded above and below by higher velocities sands (with reduced permeability and porosity).
  • Turpening et al. used a connectivity mapping technique to predict that connectivity
  • Parra et al. used time-frequency analysis and numerical modeling integrated with well logs and petrophysics to predict sand continuity. Both interpretations were supported by unpublished pressure-test data collected by British Petroleum which demonstrated that the porous sand is connected between the detector well and the source well.
  • the concept of leaky mode regeneration was not addressed because the wavetrains were explicitly observed in the waveguide region containing the source.
  • the data to characterize the sandstone waveguide was based only on waveforms recorded when the source was placed within the waveguide at 974 feet as shown in Fig. 4(a).
  • leaky modes were not excited in the mudstone waveguide when the source was placed as shown in Fig. 4(a).
  • leaky modes are easiest to observe in a waveguide when the source is placed within the waveguide or near its interface.
  • the regeneration of leaky modes is more effective than when the source is outside the waveguide.
  • the amplitude of the leaky modes behind the head waves provides a signature characteristic that can be recognized just by observing common-source seismograms.
  • the leaky modes appear, giving a clear indication of the bed continuity.
  • Figs. 5(a)-5(d) correspond to the signatures associated with a shale waveguide surrounded by a sandstone host medium. To understand these signatures, the velocity ratio between the waveguide target and the host medium is varied.
  • the pressure synthetic seismogram for a source detector separation of 200 m, exhibits direct P-wave events which propagate in a waveguide with a P-wave velocity of 3548 m/s. The direct P-wave events arrive at the detectors after 56 ms, and they are followed by reflection events and leaky modes.
  • the full waveforms are dominated by modal wavetrains arriving at 88 ms, which travel with a group velocity of about 2272 m/s, which is less than the shear wave velocity of the sandstone host medium.
  • These wavetrains are normal modes trapped in the shale waveguide.
  • the seismic responses show that when the P-wave and S- wave velocity ratios between the shale waveguide and the host medium are decreased, in particular as the P-wave velocity ratio approaches 1, leaky modes are no longer observed.
  • this limiting P-wave velocity ratio to illustrate that normal modes can be observed in a shale waveguide when leaky modes are physically impossible.
  • the full waveforms are dominated by head waves and normal waves, which exhibit different signature characteristics than those signatures observed for greater shear wave velocity contrasts.
  • the seismic waveforms show that as the P-wave velocity contrast between the waveguide and the host medium is decreased, the presence of leaky modes is reduced in the seismograms. That is, the character of the seismic response reflects the change of the shale waveguide material property at the different detector positions and well separations.
  • the receiver borehole intercepts an inclusion, such as a pinch out or a discontinuity, in addition to the previously described events, a reflection from the end of the inclusion is also recorded. In this case, the difference between the arrival time between the direct event and the reflection event determines the distance between the receiver borehole and the end of the discontinuity.
  • the receiver borehole does not intercept the inclusion, no energy is trapped in the inclusion and the signature observed at the receiver is similar to that of the host medium, which can be slightly modified by the presence of the inclusion.
  • the seismic traces recorded at a receiver borehole intercepting the inclusion comprise head waves, direct SH-waves and pseudo-Love waves.
  • the receiver borehole does not intercept the inclusion, only the host medium signature is recorded, which can be slightly modified by the presence of the inclusion.
  • phase velocity and group velocity curves for a low- velocity layer having a thickness of 4 m and an SH-wave velocity of 2100 m/s and density of 2.5 gr/cm 3 are calculated.
  • the host medium has an SH-wave velocity of 2500 m/s and a density of 2.65 gr/m 3 .
  • the resulting curves are shown in Fig.
  • Fig. 6 shows the horizontal particle velocity component seismogram in this case.
  • the first arrivals are SH head waves, and the next events are guided waves followed by direct SH-waves. Some of these events are trapped in the waveguide and others travel at the interfaces of the inclusion.
  • the head wave, guided wave, and the direct events form a seismic signature that is typical of a continuous inclusion between two boreholes. Indeed, as shown in Fig.
  • this signature can be observed when both boreholes intercept a pinch out inclusion.
  • the first two signatures having twelve traces each, are intercepted by receiver boreholes located at 40 m and 20 m, respectively, from the discontinuity.
  • the third signature of twelve traces corresponds to that of the host medium. In this case, the receiver borehole is not intercepting the inclusion.
  • the first two signatures exhibit reflection events associated with the presence of the discontinuity.
  • the seismic signature does not contain such a reflection event as is observed in the last twelve traces.
  • the magnitude of the amplitude of the reflection part of the waveform indicates the thickness of the end part of the discontinuity. This concept is observed by comparing Figs. 8 and 9. Fig.
  • Fig. 8 is for a pinch out geometry having the smallest thickness equal to one-half meter
  • Fig. 9 is for a pinch out, or round head, having the smallest thickness equal to 2 m.
  • the magnitude of the reflection shown in Fig. 9 is much greater than the magnitude of that shown in Fig. 8.

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  • Physics & Mathematics (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Environmental & Geological Engineering (AREA)
  • Geology (AREA)
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  • General Life Sciences & Earth Sciences (AREA)
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Abstract

On décrit un procédé permettant de planifier des études de diagraphie relatives à la continuité et de détecter la présence d'une inclusion continue ou discontinue de faible vitesse dans une formation géologique souterraine. Pour détecter la présence d'une inclusion continue ou discontinue de faible vitesse, on introduit une source sismique dans un trou de sonde source situé soit au niveau d'une limite d'une inclusion de faible vitesse soit au centre de cette inclusion. A l'aide de la source sismique, de l'énergie sismique est générée en liaison avec l'inclusion de faible vitesse. L'énergie sismique se propage sous forme d'ondes sismiques dans l'inclusion de faible vitesse, cette énergie étant mesurée et enregistrée par au moins un détecteur placé dans un trou de sonde récepteur. Les ondes sismiques sont analysées pour rechercher la présence d'au moins une signature sismique à partir de laquelle on peut déterminer la distance d'une discontinuité, si toutefois il en existe une, de l'inclusion de faible vitesse par rapport au trou de sonde récepteur.
PCT/US1998/015030 1997-08-20 1998-07-21 Procede de prediction de cibles de guide d'ondes continues et discontinues dans lequel on utilise les caracteristiques de signature sismique entre les puits WO1999009435A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU84143/98A AU8414398A (en) 1997-08-20 1998-07-21 Method for predicting continuous and discontinuous waveguide targets using interwell seismic signature characteristics

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
US5611197P 1997-08-20 1997-08-20
US60/056,111 1997-08-20
US09/034,530 1998-03-03
US09/034,530 US6147929A (en) 1998-03-03 1998-03-03 Method for predicting continuous and discontinuous waveguide targets using interwell seismic signature characteristics

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN109477904A (zh) * 2016-06-22 2019-03-15 休斯敦大学系统 地震或声波频散的非线性信号比较和高分辨率度量

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4783771A (en) * 1986-03-18 1988-11-08 Chevron Research Company Nondestructive downhole seismic vibrator source and processes of utilizing the vibrator to obtain information about geologic formations
US5144590A (en) * 1991-08-08 1992-09-01 B P America, Inc. Bed continuity detection and analysis using crosswell seismic data

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4783771A (en) * 1986-03-18 1988-11-08 Chevron Research Company Nondestructive downhole seismic vibrator source and processes of utilizing the vibrator to obtain information about geologic formations
US5144590A (en) * 1991-08-08 1992-09-01 B P America, Inc. Bed continuity detection and analysis using crosswell seismic data

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
M. LOU ET AL.: "Guided-Wave progagation between boreholes", THE LEADING EDGE, July 1992 (1992-07-01), pages 34 - 37, XP002084276 *

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN109477904A (zh) * 2016-06-22 2019-03-15 休斯敦大学系统 地震或声波频散的非线性信号比较和高分辨率度量

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