CN110344801B - Fracturing operation method for combustible ice exploitation, exploitation method and exploitation system - Google Patents
Fracturing operation method for combustible ice exploitation, exploitation method and exploitation system Download PDFInfo
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- 238000000034 method Methods 0.000 title claims abstract description 42
- 238000002347 injection Methods 0.000 claims abstract description 80
- 239000007924 injection Substances 0.000 claims abstract description 80
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 claims abstract description 36
- 238000000605 extraction Methods 0.000 claims abstract description 21
- 239000003345 natural gas Substances 0.000 claims abstract description 17
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 70
- 238000004519 manufacturing process Methods 0.000 claims description 54
- 230000015572 biosynthetic process Effects 0.000 claims description 29
- 239000007788 liquid Substances 0.000 claims description 24
- 239000011148 porous material Substances 0.000 claims description 24
- 238000000926 separation method Methods 0.000 claims description 15
- 239000012530 fluid Substances 0.000 claims description 14
- 238000005553 drilling Methods 0.000 claims description 12
- 239000004576 sand Substances 0.000 claims description 12
- 230000006837 decompression Effects 0.000 claims description 10
- 230000008018 melting Effects 0.000 claims description 9
- 238000002844 melting Methods 0.000 claims description 9
- 230000001105 regulatory effect Effects 0.000 claims description 8
- 238000012856 packing Methods 0.000 claims description 6
- 230000001276 controlling effect Effects 0.000 claims description 5
- 238000005065 mining Methods 0.000 claims description 5
- 239000000284 extract Substances 0.000 claims description 4
- 238000009434 installation Methods 0.000 claims description 4
- 230000003750 conditioning effect Effects 0.000 claims description 2
- 230000000149 penetrating effect Effects 0.000 claims description 2
- 230000007774 longterm Effects 0.000 abstract description 2
- 238000005755 formation reaction Methods 0.000 description 25
- 238000010586 diagram Methods 0.000 description 9
- 238000003860 storage Methods 0.000 description 6
- 230000000694 effects Effects 0.000 description 5
- 239000007789 gas Substances 0.000 description 4
- 238000009826 distribution Methods 0.000 description 3
- 239000000155 melt Substances 0.000 description 3
- 230000003213 activating effect Effects 0.000 description 2
- 239000003795 chemical substances by application Substances 0.000 description 2
- 230000008014 freezing Effects 0.000 description 2
- 238000007710 freezing Methods 0.000 description 2
- 238000004321 preservation Methods 0.000 description 2
- 238000011084 recovery Methods 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
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- 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
- E21B41/00—Equipment or details not covered by groups E21B15/00 - E21B40/00
- E21B41/0099—Equipment or details not covered by groups E21B15/00 - E21B40/00 specially adapted for drilling for or production of natural hydrate or clathrate gas reservoirs; Drilling through or monitoring of formations containing gas hydrates or clathrates
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- 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
- E21B43/01—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells specially adapted for obtaining from underwater installations
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- 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
- E21B43/25—Methods for stimulating production
- E21B43/26—Methods for stimulating production by forming crevices or fractures
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- 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
- E21B43/30—Specific pattern of wells, e.g. optimising the spacing of wells
- E21B43/305—Specific pattern of wells, e.g. optimising the spacing of wells comprising at least one inclined or horizontal well
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Abstract
The invention discloses a fracturing operation method applied to single wells and double wells, a corresponding natural gas exploitation method and a system device used during exploitation, wherein the fracturing operation is carried out in a pressurization and depressurization paired mode, most fracturing cracks are finally pointed to a branch well hole through the guidance of a negative pressure gradient field, the damage of the fracturing operation to an overlying stratum is greatly reduced, the overlying layer of combustible ice is protected, and the method is one of the guarantee for the safe exploitation of the combustible ice; the exploitation control range of the combustible ice resource by a single well is greatly improved, the single well yield is improved, and the well spacing density is reduced. During exploitation, pressurization and depressurization paired push-pull type work is also adopted between the injection branch well and the extraction branch well, so that smoothness of injection to an extraction seepage channel is kept, secondary icing and filling of fracturing cracks are prevented, and long-term stable exploitation of combustible ice natural gas is maintained.
Description
Technical Field
The invention relates to an energy exploitation technology, in particular to a method for fracturing a stratum by applying a pressurizing and depressurizing paired pressure field, and a method and a system for exploiting combustible ice stratum natural gas by using the fracturing operation method.
Background
Pressure reduction (negative pressure) mining is to reduce the pressure in a well bore and locally break the temperature and pressure environment for storing combustible ice so as to melt the combustible ice. This mining process takes into account a number of factors. As the combustible ice melts, gas is formed and the local pressure increases; the combustible ice melts and absorbs heat to reduce the local temperature; the local temperature and pressure environment quickly returns to the freezing temperature and pressure conditions, causing the production process to stop. In order to make the exploitation of combustible ice more continuous, the fracturing operation naturally becomes an important means, however, the fracturing operation method for the exploitation of combustible ice has the following two problems:
firstly, because the pressure is recovered in a short radial distance, the space range meeting the melting pressure condition of the combustible ice is very small, and the melting area is a radial cylindrical space range from the well wall to dozens of centimeters by taking a uniform infinite thick stratum as an example for analysis. If the perforation channel is also considered as an extension of the wellbore, the control radius of a well is only approximately equal to the perforation radius plus a few tens of centimeters.
Secondly, the fracturing operation becomes an effective means for expanding the single-well exploitation range, and after the fracturing operation, the control radius of one well is about larger than the range covered by the fracturing crack. However, since the combustible ice overlying strata is thin and soft, high-strength fracturing operation like shale gas exploitation cannot be adopted to protect the combustible ice overlying strata from being damaged. In addition, due to the secondary icing of combustible ice, the cracks generated by the fracturing operation are quickly filled, so that the effect generated by the fracturing operation cannot be continuously maintained.
Disclosure of Invention
In order to solve the problems, the invention provides a method for fracturing a stratum by using a pair of pressure fields of pressurization and depressurization, and a method and a system for exploiting combustible ice stratum natural gas by using the fracturing operation method.
A method of fracturing operations for use in a single well, comprising the steps of:
1) drilling at least one production branch borehole at a production layer of the formation and at least one injection branch borehole at an injection layer; a plurality of injection pore canals are formed in pipelines of the production branch well hole and the injection branch well hole so that fracturing fluid can flow in or out;
2) after casing running operation, well cementation operation and installation of an inlet device are finished, a pressure-increasing pipeline and a plug for fracturing packing are placed into a casing between a production branch well hole and an injection branch well hole along the casing;
3) the pressure increasing pipe penetrates through a plug on the path to be communicated with the injection branch well hole; the booster pipe is connected with a booster pump, so that the booster pump is communicated with the injection branch well hole; the annular space between the pressure increasing pipe and the sleeve is a pressure reducing channel; one end of the pressure reducing pipe is connected with the pressure reducing pump, and the other end of the pressure reducing pipe is communicated with the production branch well hole through the pressure reducing channel;
4) starting a booster pump and a pressure reducing pump to perform fracturing operation: the booster pump injects fracturing fluid into the stratum through the injection branch well hole, and a positive pressure gradient field is formed in the stratum around the injection branch well hole; the pressure reducing pump extracts liquid from the production branch well hole through the pressure reducing channel, and a negative pressure gradient field is formed in the stratum around the production branch well hole; on a path from the injection branch well hole to the extraction branch well hole, the positive and negative pressure gradient fields are mutually pushed and pulled to be strengthened to generate a larger fracture; in other formation zones, the positive and negative pressure gradient fields cancel each other, producing smaller or no fracture fractures.
The method for exploiting the natural gas in the combustible ice stratum by applying the fracturing operation method comprises the following steps: after the fracturing operation is finished, the pressure increasing pipe is replaced by a warm water pipe, the pressure reducing pipe is replaced by an air-water channel, the warm water pipe is connected with a warm water regulation and control system, and the air-water channel is connected with a separation lifting system;
the warm water regulation and control system conveys injection liquid into the injection branch well bore through a warm water pipe, the injection liquid seeps into the production branch well bore through a large crack, combustible ice melting liquid in the stratum flows into the production branch well bore under the driving of pressure difference, and natural gas flows into the separation lifting system through a gas-water channel.
A method of fracturing operations in two wells, comprising the steps of:
1) drilling a left well and a right well, wherein the left well is used for production, and the right well is used for injection;
drilling at least one extraction branch well hole in the left well, drilling at least one injection branch well hole in the right well, and opening a plurality of injection pore canals in pipelines of the extraction branch well hole and the injection branch well hole so that fracturing fluid can flow in or out;
2) completing casing running operation, well cementation operation and inlet device installation operation;
3) installing plugs in the wells respectively, and communicating the output ends of the pressure reducing pipes with the production branch well bores after sequentially penetrating the plugs on the paths in the production wells on the left; in the right well, the output end of the booster pipe sequentially penetrates through the plugs on the path and then is communicated with the injection branch well hole;
4) starting a booster pump and a pressure reducing pump to perform fracturing operation; the booster pump injects fracturing fluid into the stratum through the injection branch well hole to form a positive pressure gradient field in the surrounding stratum; the decompression pump extracts liquid from the production branch well hole through the decompression channel to form a negative pressure gradient field in the surrounding stratum; on the path from the injection branch well hole to the extraction branch well hole, the positive and negative pressure gradient fields push and pull each other to strengthen and generate a larger fracture; in other formation zones, the positive and negative pressure gradient fields cancel each other to create smaller or no fracture fractures.
The method for exploiting the combustible ice natural gas by applying the two-well fracturing operation method comprises the following steps: the pressure increasing pipe is replaced by a warm water pipe, the pressure reducing pipe is replaced by an air-water channel, the upper end of the warm water pipe is connected with a warm water regulation and control system, and the upper end of the air-water channel is connected with a separation lifting system; the warm water regulation and control system conveys injection liquid into the injection branch well bore through a warm water pipe, the injection liquid seeps into the production branch well bore through a large crack, combustible ice melting liquid in the stratum flows into the production branch well bore under the driving of pressure difference, and natural gas flows into the separation lifting system through a gas-water channel.
The exploitation system is applied to a vertical well and comprises a sleeve, a warm water regulation and control system and a separation and lifting system, wherein a warm water pipe and an underground regulation and control device are arranged in the sleeve, the upper end of the warm water pipe is connected with the warm water regulation and control system, and the lower end of the warm water pipe is connected with the underground regulation and control device; a gas-water channel is formed in the space between the sleeve and the warm water pipe and is connected with the separation and lifting system;
the stratum at the extraction branch well hole is a combustible ice reservoir, and the stratum at the injection branch well hole is a pore reservoir;
the method comprises the following steps that sand control screen pipes are respectively arranged in sleeves at a combustible ice reservoir stratum and a pore reservoir stratum, packing devices are respectively arranged at the upper end and the lower end of each sand control screen pipe, and a plurality of through holes for liquid to flow are formed in the sand control screen pipes; the downhole conditioning device is disposed within the casing at the pore reservoir.
The invention has the beneficial effects that:
(1) the fracturing operation is carried out in a pressurization and depressurization paired mode, most fracturing cracks are finally directed to the extraction branch well hole through the guidance of the negative pressure gradient field, the damage of the fracturing operation to the overlying strata is greatly reduced, the overlying layer of the combustible ice is protected, and the method is one of the guarantees of the safe exploitation of the combustible ice;
(2) fracturing operation is carried out in a pressurization and depressurization pairing mode, the exploitation control range of combustible ice resources by a single well is greatly enlarged, the yield of the single well is increased, and the well distribution density is reduced;
(3) during exploitation, pressurization and depressurization paired push-pull type work is also adopted between the injection branch well and the extraction branch well, so that smoothness of injection to an extraction seepage channel is kept, secondary icing and filling of fracturing cracks are prevented, and long-term stable exploitation of combustible ice natural gas is maintained.
(4) When the fracture recovers after production stop, secondary fracturing operation along the old fracture can be performed, and the secondary fracturing operation cost is reduced.
(5) In the process of exploitation, if the production rate is reduced seriously due to blockage, the injection branch well hole and the extraction branch well hole can be exchanged, namely the original injection branch well hole is used as an extraction branch well hole, the original extraction branch well hole is used as an injection branch well hole, positive-negative push-pull type pressurization is carried out, so that fluid flows in the stratum reversely, and the effect of clearing the blockage is achieved.
Drawings
FIG. 1 is a graph of temperature and pressure conditions for combustible ice formation and preservation (common general knowledge in the art);
FIG. 2 is a graph of downhole pressure radial variation estimation results;
FIG. 3 is a graph of downhole pressure gradient radial variation estimation results;
FIG. 4 is a schematic diagram of a method of a pressurized and depressurized paired fracturing operation;
FIG. 5 is a schematic diagram illustrating the effectiveness of a pair of fracturing operations with increased and decreased pressure;
FIG. 6 is a schematic diagram of a system for exploiting natural gas from combustible ice formations using a pressure and pressure enhanced coupled fracturing operation;
FIG. 7 is a schematic diagram of a system for exploiting natural gas from combustible ice formations in a vertical well by applying a pair of pressurized and depressurized fracturing operations;
FIG. 8 is a schematic diagram of a method for performing a pair-wise fracturing operation with increased pressure and reduced pressure between two wells;
FIG. 9 is a schematic diagram of the fracturing effect of a pair of fracturing operations with pressurization and depressurization between two wells.
In the figure: 11 is a booster pump, 12 is a decompression pump, 13 is a booster pipe, 14 is a negative pressure pipe, 16 is a production branch well hole, 17 is an injection branch well hole, 18 is a perforation hole, 19 is a plug, 21 is a warm water regulating system, 22 is a separation lifting system, 23 is a warm water pipe, 24 is a gas-water channel, 25 is a sand control screen pipe, 26 is a packing device, 27 is an underground regulating device, 3 is a sleeve pipe, 4 is a combustible ice reservoir, 5 is a pore reservoir and 6 is a hot water layer.
Detailed Description
The invention is further explained below with reference to the drawings.
Fig. 1 shows temperature and pressure conditions for combustible ice formation and preservation. Negative pressure mining is to reduce the pressure in a well bore and locally break the temperature and pressure environment for storing combustible ice so as to melt the combustible ice. This mining process takes into account a number of factors. The pressure can be increased along with the formation of methane gas by melting of the combustible ice, the combustible ice melts and absorbs heat to reduce the local temperature, and the local temperature and pressure environment can quickly return to the icing area; it is necessary to continually lift the wellbore fluid to maintain a negative pressure differential environment while replenishing thermal energy and materials. And under the action of negative pressure difference, when the pressure difference gradient is greater than the fracture pressure difference critical value, the stratum is fractured. The formation may locally collapse under the combined action of sand production and fracturing. The size of the negative pressure difference control area directly determines the output of a single well, directly determines the density of a well pattern, and directly determines whether a horizontal well needs to be utilized or not.
After applying a negative pressure differential to the formation, the formation reacts in the same manner as the fracturing process. Except that conventional fracturing is a positive pressure differential. For a wellbore traversing an infinitely thick formation, the pressure distribution is a radial one-dimensional problem, ignoring the pressure transmitted by the fluid in the pores and fractures, the radial radiusrPressure of point
Can be roughly written as:
wherein,
is the pressure of undisturbed stratum, and for a unconsolidated stratum which is hundreds of meters below the surface of a sea bed,
approximation, etcThe hydrostatic pressure of the water therein;
is the wellbore pressure;
is the borehole radius.
Fig. 2 is a simplified estimate of radial variation in pressure. Wherein the undisturbed formation pressure is 10MPa (equivalent to the pressure at the water depth of 1000 m), the borehole pressure is 6MPa (equivalent to the pressure at the water depth of 600 m), the borehole radius is 0.1m, and the used model is in a radial one-dimensional mode. The solid line shown in the figure is the radial variation of the pressure calculated according to formula (i). When the pressure transfer effects of the fluids in the pore channels and fractures are considered, as shown by the dashed lines in FIG. 2, the calculation equations are much more complex and related to a number of other formation parameters. It can be seen from the figure that the range of pressure meeting the melting pressure condition of combustible ice is not very large due to the radial recovery of pressure, and when the critical pressure is 9MPa, the melting area is a radial range from the well wall to 25cm, as analyzed by taking fig. 2 as an example. If the perforation tunnel is also considered as an extension of the wellbore, the control radius of a well is approximately equal to the perforation radius plus 25 cm. If the fracturing is taken into account, the control radius of a well is approximately equal to the extent covered by the fracturing. However, large-scale fracturing such as shale gas production cannot be used because the combustible ice overlying strata are thin and soft. In addition, the cracks generated by the fracturing are quickly filled due to the secondary freezing of combustible ice.
During the decompression exploitation of combustible ice in the stratum, the stratum may be broken under the action of negative pressure difference. The pressure gradient in the stratum can be calculated in a simulation mode, and the pressure distribution of the stratum is a radial one-dimensional problem under the conditions that the borehole penetrates through an infinite-thickness stratum and the fluid transfer pressure in pores and cracks is neglectedrThe pressure gradient of a spot can be roughly written as:
FIG. 3 is a simplified estimate of radial variation of pressure gradient. In the figure, the undisturbed formation pressure is 10Mpa (equivalent to a pressure at a water depth of 1000 m), the borehole pressure is 6Mpa (equivalent to a pressure at a water depth of 600 m), the borehole radius is 0.1m, and the model used is one-dimensional in the radial direction. The solid line in fig. 3 is the pressure gradient calculated according to formula (ii) as shown by the dashed line when pores and fractures are considered. If the pressure gradient is greater than the fracture threshold of the formation, the formation fractures, creating a fracture. The stratum generally has a sand production critical pressure gradient and a fracture critical pressure gradient, and the well controlled pressure gradient in the stratum is one of important contents for controlling the exploitation process of the combustible ice. Differential pressure control may be achieved by injecting fluid into the formation to replenish the deficit.
Example 1
The invention works best with horizontal multilateral wells. The fracturing method shown in fig. 4 and 5 comprises the following fracturing steps:
1) horizontally drilling a production branch borehole 16 at the position of the combustible ice storage layer 4, and horizontally drilling an injection branch borehole 17 at the pore storage layer 5 below the combustible ice storage layer 4; a plurality of injection pore canals 18 are arranged in the production branch well hole 16 and the injection branch well hole 17 to allow pressure to be released;
2) well placing a casing 3 in a vertical shaft, well cementing and installing an inlet device;
3) lowering the plug 19 and the booster pipe 13 along the casing 3, wherein the booster pipe 13 sequentially passes through the plug 19 on the path and then is communicated with the injection branch well hole 17; the booster pipe 13 is connected with the booster pump 11;
the annular space between the pressure increasing pipe 13 and the sleeve 3 is a negative pressure channel; one end of the negative pressure pipe 14 is connected to the pressure reducing pump, and the other end is connected to the negative pressure channel, so as to communicate with the production branch wellbore 16;
4) the booster pump 11 and the decompression pump 12 are started. With reference to fig. 5, a schematic diagram of positive and negative pressure versus fracturing effect: the production branch well 16 is communicated with the decompression pump 12, and the injection branch well 17 is communicated with the booster pump 11; in the stratum from the injection branch borehole 16 to the extraction branch borehole 17, the positive and negative pressure fields are mutually pushed and pulled to strengthen, and a larger fracturing fracture is generated; in other areas, the positive and negative pressure fields are mutually reduced, and small fracturing cracks or even no fracturing cracks are generated. Because positive pressure amplitudes will generally be greater than negative pressure amplitudes, the fractures below the injection lateral wellbore 17 are medium and the fractures above the production lateral wellbore 16 are smaller.
To this end, after the above-described fracturing operation, there appear in the formation respective large fractures, medium fractures and small fractures, the large fractures appearing in the formation between the production lateral wellbore 16 and the injection lateral wellbore 17, the medium fractures appearing in the formation below the injection lateral wellbore 17, and the small fractures appearing in the formation above the production lateral wellbore 16.
FIG. 6 is a schematic diagram of a positive and negative pressure versus post-fracturing production system: the positive pressure pipe 13 in the fracturing operation is changed into a warm water pipe 23, the negative pressure pipe 14 is changed into a gas-water channel 24, a branch well 16 is extracted and communicated with a separation lifting system 22, and an injection branch well 17 is communicated with a warm water regulation and control system 21 to realize warm water suction, heating and pressurization. The injection liquid seeps to the production branch well bore 16 through the large crack, heat energy and an activating agent are transferred to the combustible ice reservoir 4, and meanwhile the warm water injection liquid can supplement the shortage of stratum substances.
FIG. 7 is a schematic diagram of a system for exploiting natural gas from a combustible ice formation in a vertical well by applying a pressurization and depressurization paired fracturing operation method: the casings 3 at the combustible ice reservoir 4 and the pore reservoir 5 are respectively provided with a sand control screen 25, the upper end and the lower end of each sand control screen 25 are respectively provided with a packing device 26, and the sand control screens 25 are provided with a plurality of through holes for liquid to flow. A downhole regulating device 27 is installed in the casing 3 at the pore reservoir 5, and the downhole regulating device 27 regulates the speed and the injection amount of the warm water liquid into the pore reservoir 5. When deep formation hot water is available, the deep formation hot water flows simultaneously from below into the pore reservoir 5.
Example 2
The fracturing method shown in fig. 8 is carried out in multiple wells, two wells for example. The method is implemented between two wells, and comprises the following steps:
1) two wells are drilled, the left one to the extraction site of the combustible ice reservoir 4 and the right one to the injection site of the pore reservoir 5.
Drilling a horizontal production branch borehole 16 at the position of the combustible ice storage layer 4, and drilling a horizontal injection branch borehole 17 at the pore storage layer 5 below the combustible ice storage layer 4; a plurality of injection pore canals 18 are arranged in pipelines of the production branch well hole 16 and the injection branch well hole 17 to allow pressure to be released;
2) respectively placing a casing 3 in a left well and a right well, well cementing and installing an inlet device;
3) installing plugs 19 in the left well and the right well respectively, wherein as shown in fig. 8, in the left well, the output end of the negative pressure pipe 14 sequentially passes through the plugs 19 on the path and then is communicated with the production branch well hole 16; in the right well, the output end of the booster pipe 13 sequentially passes through the plugs 19 on the path and then is communicated with the injection branch well hole 17;
4) the booster pump 11 and the decompression pump 12 are started. The production branch well 16 is communicated with the decompression pump 12, and the injection branch well 17 is communicated with the booster pump 11; in the stratum from the injection branch borehole 16 to the extraction branch borehole 17, the positive and negative pressure fields are mutually pushed and pulled to strengthen, and a larger fracturing fracture is generated; in other areas, the positive and negative pressure fields are mutually reduced, and small fracturing cracks or even no fracturing cracks are generated. Because positive pressure amplitudes will generally be greater than negative pressure amplitudes, the fracture below the injection lateral 17 is medium and the fracture above the production lateral 16 is small.
FIG. 9 is a positive and negative pressure versus fracturing recovery method applied in two wells: the positive pressure pipe 13 in the fracturing operation is changed into a warm water pipe 23, and the negative pressure pipe 14 is changed into a gas-water channel 24. The production branch well 16 is communicated with a separation and lifting system 22 through a gas-water channel 24, and the injection branch well 17 is communicated with a warm water regulation and control system 21 through a warm water pipe 23. The warm water injection liquid seeps to the production branch well bore 16 through the large fracturing fracture, heat energy and an activating agent are transferred to the combustible ice reservoir 4, and meanwhile the warm water injection liquid can supplement the shortage of stratum substances.
Claims (5)
1. A method of fracturing operations, comprising the steps of:
1) drilling at least one production branch borehole at a production layer of the formation and at least one injection branch borehole at an injection layer; a plurality of injection pore canals are formed in pipelines of the production branch well hole and the injection branch well hole so that fracturing fluid can flow in or out;
2) after casing running operation, well cementation operation and installation of an inlet device are finished, a pressure-increasing pipeline and a plug for fracturing packing are placed into a casing between a production branch well hole and an injection branch well hole along the casing;
3) the pressure increasing pipe penetrates through the plug and is communicated with the injection branch well hole; the booster pipe is connected with a booster pump, so that the booster pump is communicated with the injection branch well hole; the annular space between the pressure increasing pipe and the sleeve is a pressure reducing channel; one end of the pressure reducing pipe is connected with the pressure reducing pump, and the other end of the pressure reducing pipe is communicated with the production branch well hole through the pressure reducing channel;
4) starting a booster pump and a pressure reducing pump to perform fracturing operation: the booster pump injects fracturing fluid into the stratum through the injection branch well hole, and a positive pressure gradient field is formed in the stratum around the injection branch well hole; the pressure reducing pump extracts liquid from the production branch well hole through the pressure reducing channel, and a negative pressure gradient field is formed in the stratum around the production branch well hole; on a path from the injection branch well hole to the extraction branch well hole, the positive and negative pressure gradient fields are mutually pushed and pulled to be strengthened to generate a larger fracture; in other formation zones, the positive and negative pressure gradient fields cancel each other, producing smaller or no fracture fractures.
2. A method of fracturing operations, comprising the steps of:
1) drilling a left well and a right well, wherein the left well is used for production, and the right well is used for injection;
drilling at least one extraction branch well hole in the left well, drilling at least one injection branch well hole in the right well, and opening a plurality of injection pore canals in pipelines of the extraction branch well hole and the injection branch well hole so that fracturing fluid can flow in or out;
2) completing casing running operation, well cementation operation and inlet device installation operation;
3) installing plugs in the wells respectively, and communicating the output ends of the pressure reducing pipes with the production branch well bores after sequentially penetrating the plugs on the paths in the production wells on the left; in the right well, the output end of the booster pipe sequentially penetrates through the plugs on the path and then is communicated with the injection branch well hole;
4) starting a booster pump and a pressure reducing pump to perform fracturing operation; the booster pump injects fracturing fluid into the stratum through the injection branch well hole to form a positive pressure gradient field in the surrounding stratum; the decompression pump extracts liquid from the production branch well hole through the decompression channel to form a negative pressure gradient field in the surrounding stratum; on the path from the injection branch well hole to the extraction branch well hole, the positive and negative pressure gradient fields push and pull each other to strengthen and generate a larger fracture; in other formation zones, the positive and negative pressure gradient fields cancel each other to create smaller or no fracture fractures.
3. A method for exploiting natural gas from a combustible ice formation by applying the fracturing operation method of claim 1, wherein: after the fracturing operation is finished, the pressure increasing pipe is replaced by a warm water pipe, the pressure reducing pipe is replaced by an air-water channel, the warm water pipe is connected with a warm water regulation and control system, and the air-water channel is connected with a separation lifting system;
the warm water regulation and control system conveys injection liquid into the injection branch well bore through a warm water pipe, the injection liquid seeps into the production branch well bore through a large crack, combustible ice melting liquid in the stratum flows into the production branch well bore under the driving of pressure difference, and natural gas flows into the separation lifting system through a gas-water channel.
4. A method for exploiting combustible ice natural gas by applying the fracturing operation method of claim 2, wherein:
the pressure increasing pipe is replaced by a warm water pipe, the pressure reducing pipe is replaced by an air-water channel, the upper end of the warm water pipe is connected with a warm water regulation and control system, and the upper end of the air-water channel is connected with a separation lifting system;
the warm water regulation and control system conveys injection liquid into the injection branch well bore through a warm water pipe, the injection liquid seeps into the production branch well bore through a large crack, combustible ice melting liquid in the stratum flows into the production branch well bore under the driving of pressure difference, and natural gas flows into the separation lifting system through a gas-water channel.
5. A production system for producing combustible ice natural gas by applying the fracturing operation method according to claim 1, wherein: the mining system is applied to a vertical well and comprises a sleeve, a warm water regulating and controlling system and a separation and lifting system, wherein a warm water pipe and an underground regulating and controlling device are arranged in the sleeve, the upper end of the warm water pipe is connected with the warm water regulating and controlling system, and the lower end of the warm water pipe is connected with the underground regulating and controlling device; a gas-water channel is formed in the space between the sleeve and the warm water pipe and is connected with the separation and lifting system;
the stratum at the extraction branch well hole is a combustible ice reservoir, and the stratum at the injection branch well hole is a pore reservoir;
the method comprises the following steps that sand control screen pipes are respectively arranged in sleeves at a combustible ice reservoir stratum and a pore reservoir stratum, packing devices are respectively arranged at the upper end and the lower end of each sand control screen pipe, and a plurality of through holes for liquid to flow are formed in the sand control screen pipes; the downhole conditioning device is disposed within the casing at the pore reservoir.
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