CN113187459B - Carbon dioxide acid fracturing method for ultra-deep well carbonate rock reservoir transformation - Google Patents
Carbon dioxide acid fracturing method for ultra-deep well carbonate rock reservoir transformation Download PDFInfo
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- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 title claims abstract description 204
- 239000002253 acid Substances 0.000 title claims abstract description 174
- 229910002092 carbon dioxide Inorganic materials 0.000 title claims abstract description 154
- 239000001569 carbon dioxide Substances 0.000 title claims abstract description 98
- 238000000034 method Methods 0.000 title claims abstract description 39
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 title claims abstract description 10
- 239000011435 rock Substances 0.000 title claims description 12
- 230000009466 transformation Effects 0.000 title abstract description 10
- 239000007788 liquid Substances 0.000 claims abstract description 196
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 claims abstract description 56
- 239000003638 chemical reducing agent Substances 0.000 claims abstract description 30
- 239000003381 stabilizer Substances 0.000 claims abstract description 27
- 238000000889 atomisation Methods 0.000 claims abstract description 18
- 230000008719 thickening Effects 0.000 claims abstract description 13
- 206010017076 Fracture Diseases 0.000 claims description 35
- 239000012530 fluid Substances 0.000 claims description 27
- 208000010392 Bone Fractures Diseases 0.000 claims description 26
- 230000001965 increasing effect Effects 0.000 claims description 14
- 238000005086 pumping Methods 0.000 claims description 14
- 238000010276 construction Methods 0.000 claims description 13
- 238000002347 injection Methods 0.000 claims description 12
- 239000007924 injection Substances 0.000 claims description 12
- 239000000243 solution Substances 0.000 claims description 12
- 238000012360 testing method Methods 0.000 claims description 10
- 239000002562 thickening agent Substances 0.000 claims description 7
- 239000002994 raw material Substances 0.000 claims description 6
- 238000013461 design Methods 0.000 claims description 5
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- 239000003208 petroleum Substances 0.000 claims description 2
- 239000004094 surface-active agent Substances 0.000 claims description 2
- KPUWHANPEXNPJT-UHFFFAOYSA-N disiloxane Chemical group [SiH3]O[SiH3] KPUWHANPEXNPJT-UHFFFAOYSA-N 0.000 claims 1
- 238000002360 preparation method Methods 0.000 claims 1
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- GVGUFUZHNYFZLC-UHFFFAOYSA-N dodecyl benzenesulfonate;sodium Chemical compound [Na].CCCCCCCCCCCCOS(=O)(=O)C1=CC=CC=C1 GVGUFUZHNYFZLC-UHFFFAOYSA-N 0.000 description 6
- 238000004519 manufacturing process Methods 0.000 description 6
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- DSLZVSRJTYRBFB-UHFFFAOYSA-N Galactaric acid Natural products OC(=O)C(O)C(O)C(O)C(O)C(O)=O DSLZVSRJTYRBFB-UHFFFAOYSA-N 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
- 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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- C09K8/00—Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations
- C09K8/60—Compositions for stimulating production by acting on the underground formation
- C09K8/62—Compositions for forming crevices or fractures
- C09K8/72—Eroding chemicals, e.g. acids
- C09K8/725—Compositions containing polymers
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- C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C09K8/00—Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations
- C09K8/60—Compositions for stimulating production by acting on the underground formation
- C09K8/62—Compositions for forming crevices or fractures
- C09K8/72—Eroding chemicals, e.g. acids
- C09K8/74—Eroding chemicals, e.g. acids combined with additives added for specific purposes
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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
- E21B43/16—Enhanced recovery methods for obtaining hydrocarbons
- E21B43/164—Injecting CO2 or carbonated water
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P90/00—Enabling technologies with a potential contribution to greenhouse gas [GHG] emissions mitigation
- Y02P90/70—Combining sequestration of CO2 and exploitation of hydrocarbons by injecting CO2 or carbonated water in oil wells
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Abstract
The invention belongs to the technical field of carbon dioxide sequestration and yield-increasing transformation of oil and gas reservoirs, and particularly relates to a carbon dioxide acid fracturing method for transformation of an ultra-deep well carbonate reservoir. The invention adjusts CO2The fluidity of the composite acid liquid system is controlled by the viscosity of the composite acid liquid system, and hydrochloric acid and CO with the concentration of 20 percent2The thickening drag reducer and the atomization stabilizer form acid liquor by regulating CO2The thickening drag reducer is used to obtain acid liquid with different viscosities and CO with high viscosity2The composite acid system is suitable for making complex cracks at the end parts of the main cracks; CO of medium viscosity2The composite acid system is suitable for making complex cracks in the middle of the main crack end; CO with low viscosity2The composite acid system is suitable for making complex fractures around the main fracture of the near well section. The method can effectively improve the complexity of the reservoir fractures, increase the volume of the fractures to the mining requirement, further increase the effective action range of the artificial fractures, and effectively improve the mining efficiency of the oil and gas resources of the carbonate reservoir.
Description
Technical Field
The invention belongs to the technical field of carbon dioxide sequestration and yield-increasing transformation of oil and gas reservoirs, and particularly relates to a carbon dioxide acid fracturing method for transformation of an ultra-deep well carbonate reservoir.
Background
The acid fracturing reservoir transformation technology is one of the main technical means for exploration and development at home and abroad. With the deepening of the exploration and development process, acid fracturing objects are more and more complex, such as ultra-low permeability/ultra-low permeability, special lithology, complex lithology, ultra-deep wells and the like, so that the acid fracturing difficulty is higher and higher, and the adaptability is poorer and poorer. Currently, acid fracturing is performed at home and abroad by mostly adopting an acid liquor system taking hydrochloric acid as a main body, and generally increasing the viscosity of the system to delay H in the acid liquor+The release rate of the acid rock is reduced, so that the acid liquor has longer action distance in the crack, and a better acid fracturing yield increase effect is achieved. However, the surface interfacial tension of the traditional acid system is large, the traditional acid system cannot enter some tiny natural cracks or pores, and the diffusion and penetration capacity of the traditional acid system is far inferior to that of gas, so that the produced cracks are single, the viscosity of the system is rapidly reduced particularly under high temperature and high pressure, the acid rock reaction rate is accelerated, the acid fracturing modification volume is greatly reduced, and the acid fracturing modification effect is reduced.
Along with the more and more complicated (high temperature, high pressure, hypotonic etc.) of transformation object, the fracture form that traditional acid fracturing technique made is single, and the transformation volume is limited, and this is very unfavorable for the later stage production of oil gas well. Therefore, many oil and gas wells are difficult to obtain ideal yield increasing effect after acid fracturing modification.
At present, a system framework in the prior art needs to be broken through, the complexity of reservoir fractures can be effectively improved, and a reservoir transformation method of a complex fracture system is obtained, so that the efficient development of oil and gas resources in a complex reservoir is realized. Therefore, how to improve the fracture degree of the reservoir in the acid fracturing modification and effectively increase the complexity of the fracture can be seen, and the improvement of the swept range of the reservoir modification is a key technical requirement for the development of the complex reservoir. In addition, the conventional hydraulic fracturing technology also faces the problems of reservoir damage, excessive water resource consumption and the like, so that the conventional hydraulic fracturing technology faces huge challenges and disputes in popularization and application. Under the circumstances, development of a novel acid fracturing modification process is urgently needed, and on the basis of effectively solving the problems of reservoir damage, water resource consumption and the like, the complexity of cracks and the modification volume of a reservoir are further improved, so that efficient development of oil and gas resources is realized.
Disclosure of Invention
The invention aims to overcome the defects of the prior art, and provides a carbon dioxide acid fracturing method for improving a carbonate reservoir of an ultra-deep well.
In order to achieve the aim, the invention provides a carbon dioxide acid fracturing method for ultra-deep well carbonate reservoir reformation, which comprises the following steps:
the method comprises the following steps: preparing;
preparing ground equipment and construction materials according to a construction design, putting a fracturing pipe column, putting an underground fracturing tool to a preset position in a shaft, installing a fracturing wellhead, connecting the ground equipment, and testing and modifying until the construction requirements are met;
step two: liquid carbon dioxide pretreatment
Injecting liquid carbon dioxide into the well bore at a small displacement in advance, and then gradually increasing the injection displacement (preferably, at 0.5m in advance)3Injecting liquid carbon dioxide into the shaft at a low discharge/min, and gradually increasing the injection discharge to 4-8m3Min) to reduce the temperature of the shaft and the bottom of the well, thereby enhancing the thermal stability of the carbon dioxide acid system; in the early stage of the process, the liquid carbon dioxide is contacted with a high-temperature reservoir, the temperature of the carbon dioxide is gradually increased to produce sufficient supercritical carbon dioxide, the characteristic of the super-high penetrating power of the supercritical carbon dioxide is exerted to reduce the fracture pressure of reservoir rocks, more natural fractures of the reservoir are communicated, the swept range of carbon dioxide acid liquor is further enlarged, and more complex secondary fractures are formed;
Step three: pumping the mixed liquid of the liquid carbon dioxide and the high-viscosity acid liquid into a well;
injecting high-viscosity fracturing fluid, namely liquid carbon dioxide and high-viscosity acid liquid into a well, wherein the liquid carbon dioxide and the high-viscosity acid liquid meet and are fully mixed in the well shaft, forming a high-viscosity carbon dioxide composite acid liquid system under the action of a thickening agent to form an artificial main crack, and along with the continuous injection of the liquid carbon dioxide and high-viscosity acid liquid mixed liquid, the length of the main crack can be further increased, and a complex crack is formed at the end part of the crack;
step four: pumping the mixed liquid of the liquid carbon dioxide and the medium viscosity acid liquid into a well;
after the high-viscosity acid liquid is injected, medium-viscosity fracturing liquid, namely liquid carbon dioxide and medium-viscosity acid liquid, is continuously injected into the cylinder, the liquid carbon dioxide and the medium-viscosity acid liquid meet and are fully mixed in the shaft, a medium-viscosity carbon dioxide composite acid liquid system is formed under the action of a thickening agent, and a complex seam network can be formed around the main crack in the middle of the crack;
step five: pumping the mixed liquid of the liquid carbon dioxide and the low-viscosity acid liquid into a well;
after the injection of the medium-viscosity acid liquid is finished, continuously injecting low-viscosity fracturing liquid, namely liquid carbon dioxide and low-viscosity acid liquid into the cylinder, wherein the liquid carbon dioxide and the low-viscosity acid liquid meet and are fully mixed in the shaft, a low-viscosity carbon dioxide composite acid liquid system is formed under the action of a thickening agent, and a complex secondary fracture network is formed around a near-well main fracture;
Step six: after the slickwater is replaced in place, closing the well for a period of time, and fully reacting acid liquor with the reservoir;
step seven: after pressure is controlled, blowout is carried out, and then oil testing and gas testing are carried out;
the high-viscosity acid liquid, the medium-viscosity acid liquid and the low-viscosity acid liquid are respectively hydrochloric acid with the concentration of 20 percent and CO2Thickening drag reducer and atomization stabilizer by adjusting CO2The thickening drag reducer is used to obtain acid liquor with different viscosities, and the CO is used2The thickening drag reducer and the atomization stabilizer can be commonly used in the petroleum industry.
Preferably, the high viscosity fracturing fluid comprises the following raw materials: liquid CO2The high-viscosity acid liquid comprises the following components: hydrochloric acid + liquid CO2CO 2-2.5% by volume2Thickening drag reducer + liquid CO21% by volume of an atomizing stabilizer;
the medium viscosity fracturing fluid comprises the following raw materials: liquid CO2+ medium mucic acid solution, medium mucic acid solution is: hydrochloric acid + liquid CO2CO volume (1% -1.5%)2Thickening drag reducer + liquid CO21% by volume of an atomizing stabilizer;
the low-viscosity fracturing fluid comprises the following raw materials: liquid CO2The low-viscosity acid liquid comprises the following components: hydrochloric acid + liquid CO2CO (0.6-1%) by volume2Thickening drag reducer + liquid CO21% by volume of an atomizing stabilizer; the concentration of the hydrochloric acid is 20 percent.
Preferably, the volume ratio of the total adding amount of the high-viscosity acid liquid, the medium-viscosity acid liquid, the low-viscosity acid liquid and the liquid carbon dioxide is (0-0.5): (0-0.5): (0.1-0.5): 1.
preferably, in the carbon dioxide acid fracturing method, the addition amounts of the high viscous acid liquid, the medium viscous acid liquid and the low viscous acid liquid are selected according to the length of the main fracture required by reservoir design, when the length of the main fracture is below 60 meters, only the low viscous acid liquid needs to be added (i.e., the third step and the fourth step are omitted), when the length of the main fracture is 60-100 meters, the medium viscous acid liquid and the low viscous acid liquid need to be added (i.e., the third step is omitted), and when the length of the main fracture is greater than 100 meters, the high viscous acid liquid, the medium viscous acid liquid and the low viscous acid liquid need to be added.
More preferably, when the length of the crack is more than 100 meters, the volume ratio of the high-viscosity acid liquid, the medium-viscosity acid liquid to the total amount of the liquid carbon dioxide is 0.375: 0.25: 0.125: 1;
more preferably, when the length of the crack is 60-100 m, the volume ratio of the high-viscosity acid liquid, the medium-viscosity acid liquid and the total amount of the liquid carbon dioxide is 0: 0.29: 0.18: 1.
preferably, said CO2The thickening and drag reducing agent is a silicone polymer, more preferably polydimethylsiloxane.
Preferably, the atomization stabilizer is a compound mixture of a surfactant and a polymer, more preferably a compound mixture of an aqueous solution of Sodium Dodecyl Benzene Sulfonate (SDBS) and polyacrylamide (HPAM), wherein the concentration of the SDBS aqueous solution is 10%, and the concentration of the HPAM is 5%.
Preferably, in the third to fifth steps, the specific operations of pumping the liquid carbon dioxide and the acid solution into the well are as follows:
(1) pumping liquid carbon dioxide into a carbon dioxide pump truck through a booster pump;
(2) after being uniformly mixed in a sand mixer, 20 percent hydrochloric acid, a thickening drag reducer and an atomization stabilizer form acid liquids with different viscosities, which are respectively fed into an acid liquid pump truck;
(3) injecting the carbon dioxide in the carbon dioxide pump truck in the step (1) and the acid liquor in the acid liquor pump truck into a wellhead, and mixing the liquid carbon dioxide and the acid liquor in a cylinder;
more preferably, in the step (1), when acid liquor with different viscosities is formed, the volume ratio of the liquid carbon dioxide to the addition amount of hydrochloric acid with the concentration of 20% is more than 7: 3.
the invention is prepared by introducing CO2Combined with acid systems to form CO2Complex acid system, under reservoir conditions (temperature)>31.26 deg.C, pressure>7.43Mpa) liquid CO2Phase change to supercritical state to form supercritical CO2CO as an external phase and acid droplets as an internal phase2The atomized acid liquid system has extremely low surface tension, extremely strong fluidity and diffusivity, and has the following beneficial effects in the aspect of acid fracturing:
(1) the rock breaking capacity is strong: supercritical CO2The viscosity and the surface tension are low, the kinetic energy loss in the flowing process is small, the net pressure conduction efficiency is high, and the effective rock breaking in a far end large range can be realized.
(2) The effective spread range is large: CO in supercritical state2The pore space with small radius and weak surface with small opening degree and natural fracture can be carried with acid liquid microdroplets, and the large-range penetration can be realized in the stratum, and the effective coverage range is large.
(3) The crack morphology is complex: supercritical CO2The super-strong fluidity reduces the guiding effect of the flowing direction, and increases the complexity of cracks; and supercritical CO2Molecules tend to enter the microporosities, natural fractures, and natural facets, further increasing the complexity of the fracture system.
(4) Reducing the cracking pressure of the rock.
(5) Better retarding effect, more durable acid etching effect, and high effect on CO2The acid liquid droplets have longer action distance and wider range under the carrying action; in addition to CO2In addition to hydrochloric acid in the composite acid system, a large amount of CO2H produced by continuous combination with water2CO3The acid etching effect is more durable.
(6) The invention adjusts CO2The fluidity of the composite acid liquid system is controlled by the viscosity of the composite acid liquid system, so that the action distance of the composite acid liquid system is controlled, and the reconstruction of complex cracks in different area ranges is realized. CO with high viscosity2The composite acid system has a long action distance along the main crack and is suitable for forming a complex crack at the end part of the main crack; CO of medium viscosity 2The composite acid system has moderate acting distance along the main crack and is suitable for forming a complex crack in the middle of the main crack end; CO with low viscosity2The composite acid system has short acting distance along the main fracture and is suitable for creating complex fractures around the main fracture of the near well section.
Drawings
FIG. 1 is a schematic flow diagram of a surface operation process in the fracturing process of the example.
FIG. 2 is a schematic flow diagram of a subterranean operation process in a fracturing process of an embodiment.
3-1, 3-2, 3-3 and 3-4 are schematic diagrams of high-viscosity fracturing fluid, medium-viscosity fracturing fluid and low-viscosity fracturing fluid forming cracks in the fracturing process of the embodiment.
Detailed Description
The present invention will be described in further detail with reference to the following drawings and specific examples, which are not intended to limit the scope of the invention.
In the fracturing process, the flow diagram of the ground process is shown in figure 1, and in the injection process, liquid carbon dioxide and acid liquor added with a thickening drag reducer and an atomization stabilizer are injected into a shaft from a well head after passing through a booster pump.
In the following examples, CO2The formula of the composite acid liquid system is liquid CO2Hydrochloric acid with the concentration of 20 percent and CO2Thickening drag reducer and atomization stabilizer are respectively obtained by adjusting the dosage of the thickening drag reducer The fracturing fluid with high, medium and low viscosity is as follows:
high-viscosity fracturing fluid: liquid CO2High viscosity acid solution (high viscosity acid solution is 20% hydrochloric acid + liquid CO)2CO 2-2.5% by volume2Thickening drag reducer + liquid CO21% by volume of atomizing stabilizer);
medium-viscosity fracturing fluid: liquid CO2+ medium-viscosity acid liquid (medium-viscosity acid liquid is 20% hydrochloric acid + liquid CO)2CO volume (1% -1.5%)2Thickening drag reducer + liquid CO21% by volume of an atomizing stabilizer);
low-viscosity fracturing fluid: liquid CO2+ low viscosity acid solution (low viscosity acid solution is 20% hydrochloric acid + liquid CO)2CO (0.6-1%) by volume2Thickening drag reducer + liquid CO21% by volume of an atomizing stabilizer);
wherein CO is used2The thickening drag reducer is polydimethylsiloxane, the atomization stabilizer is a compound mixture of an aqueous solution of Sodium Dodecyl Benzene Sulfonate (SDBS) and polyacrylamide (HPAM), wherein the concentration of the SDBS aqueous solution is 10%, and the concentration of the HPAM is 5%.
In the using process, in order to ensure CO2The atomization effect of the composite acid system in the reservoir, and liquid CO in each fracturing fluid in the construction process2The volume ratio of the added hydrochloric acid to the added 20% hydrochloric acid is more than 7: 3.
the invention discloses a carbon dioxide acid fracturing method for ultra-deep well carbonate reservoir transformation, which comprises the following steps of:
The method comprises the following steps: preparing;
preparing ground equipment and construction materials according to construction design, putting a fracturing pipe column, putting an underground fracturing tool into a preset position in a shaft, installing a fracturing wellhead, connecting the ground equipment, and testing and rectifying until the construction requirements are met;
step two: liquid carbon dioxide pretreatment
In advance at 0.5m3Injecting liquid carbon dioxide into a shaft at a small discharge amount of/min, and then gradually increasing the injection discharge amount to 4-8m3Min to lower the temperature of the wellbore and the bottom of the well, thereby increasing the carbon dioxide acidThermal stability of the liquid system; in the early stage of the process, the temperature of the carbon dioxide is gradually increased through the contact of the liquid carbon dioxide and a high-temperature reservoir, sufficient supercritical carbon dioxide is produced, the characteristic of the super-strong penetrating power of the supercritical carbon dioxide is exerted to reduce the fracture pressure of reservoir rocks, more natural fractures of the reservoir are communicated, the swept range of carbon dioxide acid liquid is further enlarged, and more complex secondary fractures are formed;
step three: high-viscosity acid liquid is pumped into the well
After the second step is carried out to a certain degree, pumping high-viscosity acid liquid into the well to form an artificial main crack, wherein the schematic diagram is shown in figure 3-1;
Step four: pumping the mixed liquid of the liquid carbon dioxide and the high-viscosity acid liquid into a well;
and continuously injecting liquid carbon dioxide and high-viscosity acid liquid into the wellbore, wherein the liquid carbon dioxide and the high-viscosity acid liquid meet and are fully mixed in the wellbore, and under the action of the thickening agent, a high-viscosity carbon dioxide composite acid liquid system is formed, so that the length of the main crack can be further increased, and a complex crack is formed at the end part of the crack, and the schematic diagram is shown in fig. 3-2.
Step five: pumping the mixed liquid of the liquid carbon dioxide and the medium viscosity acid liquid into a well;
after the high-viscosity acid liquid is injected, liquid carbon dioxide and medium-viscosity acid liquid are continuously injected into the cylinder, the liquid carbon dioxide and the medium-viscosity acid liquid meet and are fully mixed in the shaft, a medium-viscosity carbon dioxide composite acid liquid system is formed under the action of the thickening agent, and a complex seam network can be formed around the main crack in the middle of the crack, wherein the schematic diagram is shown in fig. 3-3.
Step six: pumping the mixed liquid of the liquid carbon dioxide and the low-viscosity acid liquid into a well;
after the injection of the medium-viscosity acid liquid is completed, liquid carbon dioxide and the low-viscosity acid liquid are continuously injected into the cylinder, the liquid carbon dioxide and the low-viscosity acid liquid meet and are fully mixed in the shaft, a low-viscosity carbon dioxide composite acid liquid system is formed under the action of the thickening agent, and a complex secondary fracture network is formed around the near-well main fracture, wherein schematic diagrams of the complex secondary fracture network are shown in fig. 3-4.
Step seven: and after the slickwater is replaced in place, closing the well for a period of time, and fully reacting the acid liquor with the reservoir.
Step eight: after the pressure is controlled, the oil and gas are released and then the operation of oil testing and gas testing is carried out.
In the above steps, the specific operations of pumping liquid carbon dioxide and acid into the well are as follows:
(1) pumping liquid carbon dioxide into a carbon dioxide pump truck through a booster pump;
(2) after being uniformly mixed in a sand mixing truck, 20 percent hydrochloric acid, a thickening drag reducer and an atomization stabilizer form acid liquor with different viscosities, and the acid liquor enters an acid liquor pump truck respectively;
(3) injecting the carbon dioxide in the carbon dioxide pump truck in the step (1) and the acid liquor in the acid liquor pump truck into a wellhead, and mixing the liquid carbon dioxide and the acid liquor in a cylinder.
The technical solution of the present invention will be described in detail with reference to specific examples.
Example 1
The method is applied to carry out acid fracturing operation on a carbonate rock reservoir of a certain well of an oil field in the west of China, wherein the depth of a target reservoir is 6009.5m, the original formation pressure is 64.99MPa, and the latest static pressure test is 58.73 MPa; reservoir temperature 143 ℃, average porosity 16.6%; average permeability 0.33 md; the actual construction parameters of the carbon dioxide acid fracturing of the ultra-deep well are as follows:
high-viscosity fracturing fluid: liquid CO2+ 20% hydrochloric acid + 2.5% CO 2Thickening drag reducer + 1% atomization stabilizer;
medium-viscosity fracturing fluid: liquid CO2+ 20% hydrochloric acid + 1.5% CO2Thickening drag reducer + 1% atomization stabilizer;
low-viscosity fracturing fluid: liquid CO2+ 20% hydrochloric acid + 1% CO2Thickening drag reducer + 1% atomization stabilizer.
The actual construction parameters of the carbon dioxide acid fracturing of the ultra-deep well are as follows:
the total consumption of liquid carbon dioxide is 400.16m3The minimum construction discharge capacity of the liquid carbon dioxide is 0.4m3Min, maximum 3.9m3Min, the minimum discharge capacity of the acid liquid end is 0 and the maximum discharge capacity is 2.2m3Min; the total discharge capacity is at least 0.4m3Min, the mostIs as large as 6.1m3/min。
TABLE 1
After the application, the daily stable gas production amount reaches more than 18 ten thousand square/day, and the stable production time exceeds 200 days.
Example 2
The method is applied to carry out acid fracturing operation on a sandstone condensate gas reservoir of a certain well of an oil field in the western China, the depth of the reservoir is 4320.8m, part of the reservoir is polluted due to early operation, and the characteristic of the condensate gas reservoir is considered. The actual construction parameters of the carbon dioxide acid fracturing of the ultra-deep well are as follows:
medium-viscosity fracturing fluid: liquid CO 2+ 20% hydrochloric acid + 1% CO2Thickening drag reducer + 1% atomization stabilizer;
low-viscosity fracturing fluid: liquid CO2+ 20% hydrochloric acid + 0.6% CO2Thickening drag reducer + 1% atomization stabilizer.
The dosage of liquid carbon dioxide is 280m3The minimum construction discharge capacity of the liquid carbon dioxide is 0.5m3Min, maximum 2.0m3Min, the minimum discharge capacity of the acid liquid end is 0 and the maximum discharge capacity is 1.2m3Min; the total discharge capacity is at least 0.4m3Min, maximum 3.2m3Min; 80.0m of viscous fracturing fluid (without carbon dioxide) in pump injection3(ii) a 50.0m of low-viscosity fracturing fluid (without carbon dioxide) injected by pump3。
After the implementation, the daily output is improved from the original 4 tons/day to 6.7 tons/day in the first 30 days, and under the condition that the oil pressure is basically stable, the process targets of blockage removal and capacity recovery are initially achieved, and a certain increase is obtainedThe production effect (67% is improved relative to the daily oil yield of 4 tons before the blockage removal operation); daily gas production is from 0.33 x 104m3Gradually rise to 1.67X 104m3(ii) a The sleeve pressure also rises gradually. The performance of the productivity and the pressure reflects that the blockage removing construction not only completes the removal of the stratum blockage and unblocks the underground seepage channel, but also reflects the energy increasing effect of carbon dioxide in the production process, and has certain auxiliary capacity for improving the flow capacity of near-well condensate oil and improving the overall extraction degree in the pressure-maintaining exploitation process of the condensate gas reservoir.
Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention, and not for limiting the protection scope of the present invention, although the present invention is described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions can be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.
Claims (5)
1. A carbon dioxide acid fracturing method for ultra-deep well carbonate rock reservoir reformation comprises the following steps:
the method comprises the following steps: preparation work
Preparing ground equipment and construction materials according to a construction design, putting a fracturing pipe column, putting an underground fracturing tool to a preset position in a shaft, installing a fracturing wellhead, connecting the ground equipment, and testing and modifying until the construction requirements are met;
step two: liquid carbon dioxide pretreatment
Injecting liquid carbon dioxide into a shaft with small discharge capacity in advance, then gradually increasing the injection discharge capacity to produce enough supercritical carbon dioxide, exerting the characteristic of ultra-high penetrating power of the supercritical carbon dioxide to reduce the fracture pressure of reservoir rock, communicating more natural fractures of the reservoir and facilitating the formation of more and more complex secondary fractures;
Step three: pumping the mixed liquid of the liquid carbon dioxide and the high-viscosity acid liquid into a well;
after the pretreatment is finished, injecting high-viscosity fracturing fluid into the well, namely: the method comprises the following steps of (1) forming an artificial main crack by using liquid carbon dioxide and high-viscosity acid liquid, increasing the length of the main crack along with continuous injection of a mixed liquid of the liquid carbon dioxide and the high-viscosity acid liquid, and forming a complex crack at the end part of the crack;
step four: pumping the mixed liquid of the liquid carbon dioxide and the medium viscosity acid liquid into a well;
after the injection of the high-viscosity acid liquid is completed, the medium-viscosity fracturing fluid is continuously injected into the cylinder, namely: liquid carbon dioxide and medium viscous acid liquid are in contact with each other and are fully mixed in a shaft, and a complex seam network is formed around the main crack in the middle of the crack;
step five: pumping the mixed liquid of the liquid carbon dioxide and the low-viscosity acid liquid into a well;
after the injection of the medium viscosity acid liquid is completed, continuously injecting the low viscosity fracturing liquid into the cylinder, namely: liquid carbon dioxide and low-viscosity acid liquor are in contact with each other and are fully mixed in a shaft, and a complex secondary fracture network is built around a near-well main fracture;
step six: after the slickwater is replaced in place, closing the well for a period of time, and fully reacting acid liquor with the reservoir;
Step seven: after controlling the pressure, the pressure is released and spraying is carried out, and then oil testing and gas testing are carried out;
the high-viscosity acid liquid, the medium-viscosity acid liquid and the low-viscosity acid liquid are respectively hydrochloric acid with the concentration of 20 percent and CO2Thickening drag reducer and atomization stabilizer by adjusting CO2The thickening drag reducer is used to obtain acid liquor with different viscosity, and the CO is2The thickening drag reducer and the atomization stabilizer can be commonly used thickening agents and stabilizing agents in the petroleum industry;
the high-viscosity fracturing fluid comprises the following raw materials: liquid CO2The high-viscosity acid liquid comprises the following components: hydrochloric acid + liquid CO22% -2.5% by volume of CO2Thickening drag reducer + liquid CO21% by volume of an atomizing stabilizer; the medium viscosity fracturing fluid comprises the following raw materials: liquid CO2+ the medium-viscosity acid liquid, the medium-viscosity acid liquid is: hydrochloric acid + liquid CO21% -1.5% by volume of CO2Thickening drag reducer + liquid CO21% by volume of an atomizing stabilizer; the low-viscosity fracturing fluid comprises the following raw materials: liquid CO2Low viscosity acid solution, low viscosity acid solutionComprises the following steps: hydrochloric acid + liquid CO20.6-1% by volume of CO2Thickening drag reducer + liquid CO21% by volume of an atomizing stabilizer; the concentration of the hydrochloric acid is 20 percent.
2. The carbon dioxide acid fracturing method of claim 1, characterized in that: the volume ratio of the total adding amount of the high-viscosity acid liquid, the medium-viscosity acid liquid, the low-viscosity acid liquid and the liquid carbon dioxide is (0-0.5): (0-0.5): (0.1-0.5): 1.
3. The carbon dioxide acid fracturing method of claim 2, wherein: in the carbon dioxide acid fracturing method, the adding amounts of the high viscous acid liquid, the medium viscous acid liquid and the low viscous acid liquid can be selected according to the length of the main fracture required by reservoir design, when the length of the main fracture is below 60 meters, only the low viscous acid liquid needs to be added, namely, the third step and the fourth step are omitted, when the length of the main fracture is 60-100 meters, the medium viscous acid liquid and the low viscous acid liquid need to be added, namely, the third step is omitted, and when the length of the main fracture is more than 100 meters, the medium viscous acid liquid and the low viscous acid liquid need to be added.
4. The carbon dioxide acid fracturing method of claim 3, wherein: in each step, the volume ratio of the liquid carbon dioxide in the high-viscosity fracturing fluid, the medium-viscosity fracturing fluid and the low-viscosity fracturing fluid to the addition of hydrochloric acid with the concentration of 20% is more than 7: 3.
5. the carbon dioxide acid fracturing method of claim 3, wherein: said CO2The thickening drag reducer is siloxane polymer, and the atomization stabilizer is a compound mixture of surfactant and polymer.
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