A method of reservoir stimulation and displacement for enhanced production by foam fracturing-gas injection synergy

Abstract

The application discloses a reservoir strengthening displacement stimulation method of foam fracturing-gas injection synergy, and belongs to the technical field of oil and gas exploitation. The method comprises the following steps: drilling a liquid injection borehole and an extraction borehole into a target reservoir; injecting CO2 foam fluid into the liquid injection borehole, performing foam fracturing on the liquid injection borehole to form a foam fracturing fracture of the liquid injection borehole, and injecting fracturing fluid into the extraction borehole to form a fracturing fracture of the extraction borehole; injecting CO2 gas into the liquid injection borehole, fully mixing the CO2 foam fluid in the foam fracturing fracture of the liquid injection borehole to form water-containing CO2 gas, and then performing displacement on the target reservoir through the wall surface of the foam fracturing fracture of the liquid injection borehole; and under the action of pressure difference, oil and gas in the target reservoir gradually flow into the fracturing fracture of the extraction borehole. The method greatly improves the swept range of gas injection and the gas injection rate, and has the advantages of low reservoir damage, small filtration loss, no fracturing fluid flowback operation and the like.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of oil and gas exploitation, and relates to a reservoir strengthening displacement stimulation method of foam fracturing-gas injection synergy. BACKGROUND

[0002] In recent years, in view of the problem of “injection difficulty and production difficulty” of low-permeability tight reservoirs, a fracturing oil displacement technology of “pressure-injection-production” integration has been proposed. Hydraulic fracturing can greatly improve the effective utilization degree of low-permeability tight reservoirs, and further improve the oil and gas recovery by combining water flooding, chemical flooding and gas flooding processes. However, the current conventional water flooding has the problems of serious water flooding and water channeling, and fluid injection difficulty; the conventional chemical displacement leads to the retention of chemical agents in the reservoir, and the displacement effect is weakened. CO2, N2 and other low-viscosity gases have stronger diffusivity than conventional water displacement and chemical displacement, and gas displacement can greatly improve the displacement sweep range and achieve CO2 storage. However, the current commonly used single-well injection mode has large near-well flow resistance, low gas displacement efficiency and small sweep range.

[0003] Patent CN 104564000B discloses a ground coalbed methane well active water-nitrogen foam composite fracturing stimulation method, the use order of the two fracturing media cannot be reversed, and the gas displacement content is not involved. Patent CN 113027407B proposes a foam-gas composite segmented fracturing formation method, which mainly utilizes the jet to form foam, and utilizes low-viscosity gas to form a complex fracture network. However, in the present application, the gas displacement process cannot form a fracturing fracture, and gas channeling is avoided. Patent CN 115541634A proposes a supercritical CO2 fracturing displacement of saline water layer simulation experiment method and system, and the foam fracturing method is not involved. SUMMARY

[0004] The present application overcomes the shortcomings of the prior art and proposes a reservoir strengthening displacement stimulation method of foam fracturing-gas injection synergy. Compared with conventional water-based fracturing fluid, the high-viscosity and low-filter-loss foam fluid can form a more straight and wider single hydraulic main fracture, and has the advantages of low reservoir damage and small filter loss. After the subsequent injection of gas, the mixed foam fluid forms a saturated water-gas body, which will diffuse from the hydraulic fracture wall to the reservoir matrix, greatly improving the gas injection rate compared with the single-well borehole, and without the need for foam fluid flowback operation.

[0005] The present application is realized by the following technical solutions:

[0006] A reservoir strengthening displacement stimulation method of foam fracturing-gas injection synergy, comprising the following steps:

[0007] Step 1: drilling a liquid injection borehole and an extraction borehole into a target reservoir;

[0008] Step 2: Inject CO2 foam fluid into the injection borehole to pressurize the injection borehole and perform foam fracturing to form a foam fracturing fracture in the injection borehole. Inject fracturing fluid into the extraction borehole to form a fracturing fracture in the extraction borehole.

[0009] Step 3: Inject CO2 gas into the injection borehole. After the CO2 gas is fully mixed with the CO2 foam fluid in the foam fracturing fracture of the injection borehole to form water-containing CO2 gas, it will displace the target reservoir through the wall of the foam fracturing fracture of the injection borehole. Under the action of pressure difference, the oil and gas in the target reservoir will gradually flow into the fracturing fracture of the extraction borehole and return to the surface through the extraction borehole.

[0010] A reservoir enhancement and displacement method synergistically combining foam fracturing and gas injection includes the following steps:

[0011] Step 1: Drill injection boreholes and extraction boreholes into the target reservoir; along the direction of the minimum horizontal principal stress of the target reservoir, drill injection boreholes into the horizontal section of injection boreholes and extraction boreholes into the horizontal section of extraction boreholes.

[0012] Step 2: Inject CO2 foam fluid into the horizontal section of the injection borehole to create a series of stresses perpendicular to the minimum horizontal stress. Foam fracturing fractures in the horizontal section of the injection borehole; local stress disturbance zone in the reservoir is formed around the foam fracturing fractures in the horizontal section of the injection borehole; hydraulic fracturing is injected into the horizontal section of the extraction borehole to form multiple fracturing fractures in the horizontal section of the extraction borehole.

[0013] Step 3: Inject CO2 gas into the horizontal section of the injection borehole. After forming saturated water CO2 gas with CO2 foam fluid in the foam fracturing fracture of the injection borehole, it will displace the target reservoir matrix. Under the action of pressure difference, the target reservoir oil and gas will gradually flow into the fracturing fracture of the horizontal section of the extraction borehole and return to the surface through the horizontal section of the extraction borehole.

[0014] Furthermore, in step three, the CO2 gas injection pressure is lower than the minimum principal stress of the target reservoir.

[0015] Furthermore, in step one, the straight-line distance between the injection borehole and the extraction borehole is greater than 1.2 times the thickness of the target reservoir.

[0016] Furthermore, the spacing between the foam fracturing fractures in the horizontal section of the injection borehole and the fracturing fractures in the horizontal section of the extraction borehole is greater than 1.2 times the target reservoir thickness, and the extended half-fracture length of the foam fracturing fractures in the horizontal section of the injection borehole and the fracturing fractures in the horizontal section of the extraction borehole is less than 3 / 4 of the spacing between the injection borehole and the extraction borehole.

[0017] Furthermore, the injection and extraction boreholes employ a multi-well sequential staged fracturing process.

[0018] Further, in step two, when the target reservoir is a strong adsorption reservoir, a liquid injection drilling hole is not drilled, N2 foam liquid is used for liquid injection drilling hole fracturing, and N2 gas or flue gas containing N2 is injected subsequently. After soaking for 60 days, the pressure of the liquid injection drilling hole is directly reduced for extraction.

[0019] Further, the fracturing fluid in step two is a conventional water-based fracturing fluid.

[0020] Further, when high permeability reservoir fracturing is required, CO2 foam fluid with 1-2% guanidine gum by mass is used for liquid injection drilling hole fracturing.

[0021] Further, when the liquid injection drilling hole foam fracturing fracture reaches a predetermined position, proppants are mixed in the CO2 foam fluid, and injection is continued to the liquid injection drilling hole foam fracturing fracture.

[0022] In step three, CO2 gas is injected into liquid injection drilling hole fracturing multi-fractures with different flow conductivity, and the characteristics of a large reduction in the width of a fracture with a high injection volume and a weakened injection capacity are utilized, so that the effect of balanced injection of a multi-fracture group is finally achieved.

[0023] The beneficial effects of the present application relative to the prior art are as follows:

[0024] The present application uses a foam fracturing-gas injection synergistic reservoir strengthening displacement extraction method, which is different from conventional single-hole injection methods, greatly improves the sweep range of gas injection, and improves the gas injection rate. After the gas is mixed with the foam in the fracturing fracture, water-containing gas is formed, which avoids the flowback of the foam fracturing fluid. Compared with conventional water-based fracturing fluid, the high-viscosity, low-filter-loss foam fluid can form a more straight, wider and longer single hydraulic main fracture, and has the advantages of low reservoir damage, small filter loss, etc. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 It is a schematic diagram of the drilling arrangement of the present application;

[0026] Figure 2 It is a schematic diagram of the foam fracturing-gas injection construction of the straight well mode of Example 1;

[0027] Figure 3 It is a schematic diagram of the foam fracturing-gas injection construction of the horizontal well mode of Example 2.

[0028] In the figure:

[0029] 1-liquid injection drilling hole; 2-fracturing drilling hole; 3-formation; 4-target reservoir; 5-liquid injection drilling hole foam fracturing fracture; 6-extraction drilling hole fracturing fracture; 7-extraction drilling hole horizontal section; 8-liquid injection drilling hole horizontal section; 9-liquid injection drilling hole foam fracturing fracture; 10-reservoir local stress disturbance area; 11-extraction drilling hole horizontal section fracturing fracture. Detailed Implementation

[0030] To make the technical problems to be solved, the technical solutions, and the beneficial effects of this invention clearer, the invention will be further described in detail with reference to the embodiments and accompanying drawings. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. The technical solutions of this invention are described in detail below with reference to the embodiments and accompanying drawings, but the scope of protection is not limited thereto.

[0031] Example 1

[0032] This embodiment provides a reservoir enhancement and displacement method synergistically combining foam fracturing and gas injection, comprising the following steps:

[0033] Step 1: See Figure 1 and Figure 2 Based on parameters such as the permeability and in-situ stress of the target reservoir 4, a fluid injection borehole 1 is drilled into the target reservoir 4 below formation 3. A production borehole 2 is arranged on each side of the fluid injection borehole 1, followed by casing cementing and perforation. The line connecting the fluid injection borehole 1 and the fracturing borehole 2 is perpendicular to the minimum horizontal in-situ stress. The direction of the two holes can be increased to 200m. The straight-line distance between the injection borehole 1 and the fracturing borehole 2 is at least 1.2 times the thickness of the target reservoir 4, so that the fracturing fractures in the injection and extraction boreholes are approximately parallel, reducing the stress shadowing effect.

[0034] Step 2: Inject CO2 foam fluid into injection borehole 1 to pressurize it and perform foam fracturing, forming foam fracturing fracture 5. When foam fracturing fracture 5 reaches the predetermined position, proppant is mixed into the CO2 foam fluid and injection continues into foam fracturing fracture 5. Then, conventional water-based high-viscosity fracturing fluid is injected into extraction borehole 2 to form extraction borehole fracturing fracture 6, and then the fracturing fluid is drained back. During the above fracturing process, the fracturing order of injection borehole 1 and extraction borehole 2 cannot be reversed.

[0035] Step 3: Inject CO2 gas into injection borehole 1, maintaining the injection pressure below the minimum stress level of the target reservoir 4. After being fully mixed with CO2 foam in the injection borehole fracturing fracture 5 to form water-containing CO2 gas, the gas is displaced by the wall of the injection borehole fracturing fracture 5 towards the target reservoir 4. Under the action of pressure difference, the oil and gas in the target reservoir 4 gradually flow into the extraction borehole fracturing fracture 6 and return to the surface through the extraction borehole 2.

[0036] Example 2

[0037] This embodiment provides a reservoir enhancement and displacement method synergistically combining foam fracturing and gas injection, comprising the following steps:

[0038] Step one: refer to Figure 1 and Figure 3 According to the permeability and ground stress of the target reservoir 4, drill the injection wellbore 1 into the target reservoir 4 at the lower part of the stratum 3, arrange one extraction wellbore 2 on each side of the injection wellbore 1, and lower the casing cementing and perforation; along the minimum horizontal principal stress direction of the target reservoir 4, drill the injection wellbore 1 into the injection wellbore horizontal section 7 and the extraction wellbore 2 into the extraction wellbore horizontal section 8; form one extraction wellbore horizontal section 8 on each side of the injection wellbore horizontal section 7.

[0039] Step two: inject CO2 foam fracturing fluid into the injection wellbore horizontal section 7 to form a series of injection wellbore horizontal section foam fracturing fractures 9 perpendicular to the minimum horizontal stress direction, when the injection wellbore horizontal section foam fracturing fractures 9 reach the predetermined position, mix proppants into the CO2 foam fluid, continue to inject into the injection wellbore horizontal section foam fracturing fractures 9; after the injection is completed, cause and form the reservoir local stress disturbance area 10 around the injection wellbore horizontal section foam fracturing fractures 9. The fracturing of the extraction wellbore horizontal section 8 uses conventional water-based fracturing fluid to form a plurality of extraction wellbore horizontal section fracturing fractures 11 and carry out flowback;

[0040] The spacing between the injection wellbore horizontal section foam fracturing fractures 9 and the extraction wellbore horizontal section fracturing fractures 11 is greater than 1.2 times the thickness of the target reservoir 4, and the extension half-fracture length of the injection wellbore horizontal section foam fracturing fractures 9 and the extraction wellbore horizontal section fracturing fractures 11 is less than 3 / 4 of the spacing between the injection wellbore 1 and the extraction wellbore 2.

[0041] Among them, the fracturing of the injection wellbore horizontal section 7 and the extraction wellbore horizontal section 8 uses an alternating segmented fracturing process, that is, after sequentially fracturing the first section fractures of the injection wellbore horizontal section 7 and the extraction wellbore horizontal section 8, then fracturing the second section fractures of the injection wellbore horizontal section 7 and the extraction wellbore horizontal section 8, the multi-fracture stress shadow effect is used to avoid the multi-fracture closing, and the horizontal well mode multi-fracture parallel expansion is realized.

[0042] Step three: inject CO2 gas into the injection wellbore horizontal section 7, after the CO2 foam fracturing fluid in the injection wellbore horizontal section foam fracturing fractures 9 is mixed with the saturated water CO2 gas, the target reservoir 4 matrix is displaced, and the oil and gas in the target reservoir 4 gradually flow into the extraction wellbore horizontal section fracturing fractures 11 under the action of pressure difference, and return to the ground through the extraction wellbore horizontal section 8.

[0043] Example 3

[0044]

[0045] ​The method of the present embodiment is the same as that of Embodiment 1, except that in step two, for strongly adsorptive reservoirs such as coal seams, the extraction drilling hole 2 is not drilled, and the injection drilling hole 1 is fractured using N2 foam liquid, followed by injection of N2 gas or flue gas with high N2 content, to avoid the target reservoir 4 from adsorbing CO2 gas expansion, resulting in reduced injection capacity, and after soaking for 60-120 days, the pressure of the injection drilling hole 1 is directly reduced for extraction.

[0046] Embodiment 4

[0047] The method of the present embodiment is the same as that of Embodiment 1, except that in step two, for strongly adsorptive reservoirs such as coal seams, the extraction drilling hole 2 is not drilled, and the injection drilling hole 1 is fractured using N2 foam liquid, followed by injection of N2 gas or flue gas with high N2 content, to avoid the target reservoir 4 from adsorbing CO2 gas expansion, resulting in reduced injection capacity, and after soaking for 60-120 days, the pressure of the injection drilling hole 1 is directly reduced for extraction.

[0048] The above is a further detailed description of the present application in combination with specific preferred embodiments, and it cannot be concluded that the specific embodiments of the present application are limited to this. For ordinary skilled persons in the technical field to which the present application belongs, without departing from the present application, a number of simple deductions or substitutions can also be made, which should be considered to belong to the scope of patent protection determined by the claims submitted.

Claims

1. A method of foam fracturing-gas injection synergistic reservoir strengthening displacement stimulation, characterized in that, The method comprises the following steps: Step one: drilling a liquid injection borehole (1) and a drainage borehole (2) into a target reservoir (4); along the direction of the minimum horizontal principal stress of the target reservoir (4), the liquid injection borehole (1) is drilled into a liquid injection borehole horizontal section (7), and the drainage borehole (2) is drilled into a drainage borehole horizontal section (8); one drainage borehole horizontal section (8) is formed on each side of the liquid injection borehole horizontal section (7); Step 2: Inject CO2 foam fluid through the horizontal section (7) of the injection borehole to form a series of stresses perpendicular to the minimum horizontal stress. A group of foam fracturing fractures in the horizontal section of the injection borehole (9); a local stress disturbance zone (10) is formed around the foam fracturing fractures (9) in the horizontal section of the injection borehole; hydraulic fracturing is injected into the horizontal section of the extraction borehole (8) to form multiple fracturing fractures in the horizontal section of the extraction borehole (11). The spacing between the foam fracturing fractures (9) of the liquid injection borehole horizontal section and the fracturing fractures (11) of the drainage borehole horizontal section is greater than 1.2 times the thickness of the target reservoir (4), and the extension half-fracture length of the foam fracturing fracture group (9) of the liquid injection borehole horizontal section and the fracturing fracture group (11) of the drainage borehole horizontal section is less than 3 / 4 of the spacing between the liquid injection borehole (1) and the drainage borehole (2); wherein the fracturing of the liquid injection borehole horizontal section (7) and the drainage borehole horizontal section (8) adopts an alternating segmented fracturing process, that is, after sequentially fracturing to form the first section fractures of the liquid injection borehole horizontal section (7) and the drainage borehole horizontal section (8), the second section fractures of the liquid injection borehole horizontal section (7) and the drainage borehole horizontal section (8) are fractured, the multi-fracture stress shadow effect is utilized to avoid the multi-fractures from approaching, and the parallel expansion of the multi-fractures in the horizontal well mode is realized; the foam fracturing fractures (9) of the liquid injection borehole horizontal section and the fracturing fractures (11) of the drainage borehole horizontal section are arranged in a staggered parallel manner and are not connected; Step three: injecting CO2 gas into the liquid injection borehole horizontal section (7), forming saturated water CO2 gas with the CO2 foam fluid in the foam fracturing fractures (9) of the liquid injection borehole horizontal section, and then displacing the target reservoir (4) matrix, under the action of pressure difference, the oil and gas of the target reservoir (4) gradually flows into the fracturing fractures (11) of the drainage borehole horizontal section, and returns to the ground through the drainage borehole horizontal section (8); in step three, the injection pressure of the CO2 gas is lower than the minimum horizontal principal stress of the target reservoir (4).

2. A method of foam-fracturing-gas injection synergized reservoir-strengthening displacement stimulation according to claim 1, characterized in that, The liquid injection borehole (1) and the drainage borehole (2) adopt a multi-well sequential segmented fracturing process, and sequentially fracture the same section fractures of different wells.

3. A method of foam-fracturing-gas injection synergized reservoir-strengthening displacement stimulation according to claim 1, characterized in that, In step two, when the target reservoir (4) is a strong adsorption reservoir, the drainage borehole (2) is not drilled, N2 foam liquid is used for fracturing of the liquid injection borehole (1), and then N2 gas or flue gas is injected, and after soaking for 60 days, the pressure of the liquid injection borehole (1) is directly reduced for drainage.

Images