Foam fracturing-gas injection synergetic reservoir enhanced displacement yield increasing method

Abstract

The invention discloses a foam fracturing-gas injection synergetic reservoir enhanced displacement yield increasing method, and belongs to the technical field of oil and gas exploitation. The method comprises the following steps: firstly, drilling a liquid injection drill hole and an extraction drill hole in a target reservoir; cO2 foam fluid is injected into the liquid injection drill hole, the liquid injection drill hole is pressurized for foam fracturing, a liquid injection drill hole foam fracturing crack is formed, and fracturing fluid is injected into the extraction drill hole to form an extraction drill hole fracturing crack; cO2 gas is injected into the liquid injection drill hole, after water-containing CO2 gas is formed after the CO2 gas is fully mixed with CO2 foam fluid in the foam fracturing crack of the liquid injection drill hole, displacement is conducted on the target reservoir through the wall face of the foam fracturing crack of the liquid injection drill hole, and oil gas in the target reservoir gradually flows into the extraction drill hole fracturing crack under the action of pressure difference; according to the invention, the sweep range of gas injection is greatly improved, and the gas injection rate is improved; the fracturing fluid has the advantages of low reservoir damage, small filter loss, no need of fracturing fluid flowback operation and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of oil and gas exploitation, and relates to a reservoir enhanced displacement and production increase method by synergizing foam fracturing and gas injection. Background Art

[0002] In recent years, the integrated “pressure-injection-production” fracturing oil and gas technology has been proposed to address the problem of “no injection and no production” in low-permeability tight reservoirs. Hydraulic fracturing can greatly improve the effective utilization of low-permeability tight reservoirs, and further improve the oil and gas recovery rate by combining water drive, chemical drive and gas drive processes. However, conventional water drive currently has serious water flooding and water channeling, and fluid injection is difficult; conventional chemical drive causes chemical agents to remain in the reservoir, and the drive effect is weakened. Low-viscosity gases such as CO2 and N2 have stronger diffusivity than conventional water drive and chemical drive. Gas drive can greatly increase the range of drive and achieve CO2 storage. However, the currently commonly used single-well injection mode has large near-well flow resistance, low gas drive efficiency, and a small range.

[0003] Patent CN 104564000B discloses a method for increasing production of ground coalbed methane wells by using active water-nitrogen foam composite fracturing. The order of using the two fracturing media cannot be reversed, and gas displacement is not involved. Patent CN 113027407 B proposes a foam-gas composite segmented fracturing formation method, which mainly uses jets to form foam and uses low-viscosity gas fracturing to form a complex fracture network. However, in the present invention, the gas displacement process cannot form fracturing cracks to avoid gas channeling. Patent CN 115541634 A proposes a simulation experimental method and system for supercritical CO2 fracturing to displace saline layers, and does not involve foam fracturing methods. Summary of the invention

[0004] The present invention overcomes the shortcomings of the prior art and proposes a reservoir enhancement displacement and production increase method with foam fracturing and gas injection synergy; compared with conventional water-based fracturing fluid, high-viscosity, low-filtration foam fluid can form a straighter and wider single hydraulic main fracture, and has the advantages of low reservoir damage and small filtration loss. The subsequently injected gas, after mixing with the foam fluid to form saturated water gas, will diffuse from the hydraulic fracture wall to the reservoir matrix, greatly improving the gas injection rate compared with single well drilling, and no foam fluid backflow operation is required.

[0005] The present invention is achieved through the following technical solutions: A foam fracturing-gas injection coordinated reservoir enhanced displacement and production increase method comprises the following steps: Step 1: Drilling injection boreholes and extraction boreholes into the target reservoir; Step 2: injecting CO2 foam fluid into the injection borehole, pressurizing the injection borehole for foam fracturing to form injection borehole foam fracturing cracks, and injecting fracturing fluid into the extraction borehole to form extraction borehole fracturing cracks; Step 3: Inject CO2 gas into the injection borehole. After being fully mixed with the CO2 foam fluid in the injection borehole foam fracturing crack to form water-containing CO2 gas, it is displaced to the target reservoir through the wall of the injection borehole foam fracturing crack. Under the action of pressure difference, the oil and gas in the target reservoir gradually flow into the extraction borehole fracturing crack and return to the ground through the extraction borehole.

[0006] A foam fracturing-gas injection coordinated reservoir enhanced displacement and production increase method comprises the following steps: Step 1: Drilling a fluid injection borehole and a drainage borehole into the target reservoir; along the direction of the minimum horizontal principal stress of the target reservoir, the fluid injection borehole is drilled into the horizontal section of the fluid injection borehole, and the drainage borehole is drilled into the horizontal section of the drainage borehole; Step 2: Inject CO2 foam fluid through the horizontal section of the injection borehole to form a series of vertical minimum horizontal ground stress The foam fracturing cracks in the horizontal section of the injection borehole are formed in the direction of the injection direction; a local stress disturbance area of ​​the reservoir is formed around the foam fracturing cracks in the horizontal section of the injection borehole; the fracturing fluid is injected into the horizontal section of the extraction borehole to form multiple fracturing cracks in the horizontal section of the extraction borehole; Step 3: Inject CO2 gas into the horizontal section of the injection borehole, and form saturated water CO2 gas with CO2 foam fluid in the foam fracturing cracks in the horizontal section of the injection borehole, and then displace it into the target reservoir matrix. Under the action of pressure difference, the oil and gas in the target reservoir gradually flow into the fracturing cracks in the horizontal section of the extraction borehole, and return to the ground through the horizontal section of the extraction borehole.

[0007] Furthermore, in step three, the injection pressure of the CO2 gas is lower than the minimum horizontal principal stress of the target reservoir.

[0008] Furthermore, in step 1, the straight-line distance between the injection borehole and the extraction borehole is greater than 1.2 times the target reservoir thickness.

[0009] Furthermore, the spacing between the foam fracturing cracks in the horizontal section of the injection borehole and the fracturing cracks 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 cracks in the horizontal section of the injection borehole and the fracturing cracks in the horizontal section of the extraction borehole is less than 3 / 4 of the spacing between the injection borehole and the extraction borehole.

[0010] Furthermore, the injection drilling and extraction drilling adopt a multi-well sequential staged fracturing process.

[0011] Furthermore, in step 2, when the target reservoir is a strong adsorptive reservoir, no extraction borehole is drilled, and N2 foam fluid is used for fluid injection drilling fracturing, followed by injection of N2 gas or flue gas containing N2. After the well is shut down for 60 days, the pressure of the fluid injection borehole is directly reduced for extraction.

[0012] Furthermore, the fracturing fluid described in step 2 is a conventional water-based fracturing fluid.

[0013] Furthermore, when high permeability reservoir fracturing is required, CO2 foam fluid with 1-2% by mass of guar gum added is used for liquid injection drilling fracturing.

[0014] Furthermore, when the liquid injection drilling foam fracturing crack reaches a predetermined position, a proppant is mixed into the CO2 foam fluid and is continuously injected into the liquid injection drilling foam fracturing crack.

[0015] In step three, CO2 gas is generally injected into multiple fractures of the injection drilling fracturing with different conductivity, taking advantage of the fact that the fracture width is greatly reduced due to high injection volume, and thus the injection capacity is weakened, ultimately achieving the effect of balanced injection of multiple fracture groups.

[0016] The beneficial effects of the present invention compared with the prior art are as follows: The present invention utilizes a reservoir enhanced displacement extraction method that uses foam fracturing and gas injection synergistically. Unlike conventional single-hole injection methods, it greatly increases the scope of gas injection and increases the gas injection rate. The gas is mixed with the foam in the fracturing crack to form water-containing gas, which avoids the backflow of the foam fracturing fluid. Compared with conventional water-based fracturing fluid, the high-viscosity, low-filtration foam fluid can form a straighter, wider, and longer single hydraulic main fracture, and has the advantages of low reservoir damage and small filtration loss. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of the drilling arrangement of the present invention; Figure 2 It is a schematic diagram of the vertical well mode foam fracturing-gas injection construction of Example 1; Figure 3 This is a schematic diagram of the foam fracturing-gas injection construction in the horizontal well mode of Example 2.

[0018] In the figure: 1-liquid injection borehole; 2-fracturing borehole; 3-formation; 4-target reservoir; 5-foam fracturing cracks in the liquid injection borehole; 6-fracturing cracks in the extraction borehole; 7-horizontal section of the extraction borehole; 8-horizontal section of the liquid injection borehole, 9-foam fracturing cracks in the horizontal section of the liquid injection borehole, 10-local stress disturbance area of ​​the reservoir, 11-fracturing cracks in the horizontal section of the extraction borehole. DETAILED DESCRIPTION

[0019] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention clearer, the present invention is further described in detail in conjunction with the embodiments and the accompanying drawings. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. The technical solutions of the present invention are described in detail below in conjunction with the embodiments and the accompanying drawings, but the scope of protection is not limited thereto.

[0020] Example 1 The present embodiment provides a method for enhancing reservoir displacement and production by synergistic foam fracturing and gas injection, comprising the following steps: Step 1: See Figure 1 and Figure 2 According to the permeability and geostress parameters of the target reservoir 4, a fluid injection borehole 1 is drilled into the target reservoir 4 at the bottom of the formation 3, and a drainage borehole 2 is arranged on both sides of the fluid injection borehole 1, and casing is lowered for cementing and perforation. The line connecting the fluid injection borehole 1 and the fracturing borehole 2 is perpendicular to the minimum horizontal geostress. 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 injection and extraction borehole fracturing cracks are approximately parallel, reducing the stress shadow effect.

[0021] Step 2: Inject CO2 foam fluid into the injection borehole 1, pressurize the injection borehole 1 for foam fracturing, form the injection borehole foam fracturing crack 5, and when the injection borehole foam fracturing crack 5 reaches the predetermined position, mix the proppant into the CO2 foam fluid, and continue to inject it into the injection borehole foam fracturing crack 5; then inject conventional water-based high-viscosity fracturing fluid into the extraction borehole 2 to form the extraction borehole fracturing crack 6, and then return the fracturing fluid; in the above-mentioned fracturing process, the fracturing order of the injection borehole 1 and the extraction borehole 2 cannot be reversed.

[0022] Step 3: Inject CO2 gas into the injection borehole 1, and keep the injection pressure below the minimum horizontal stress of the target reservoir 4 After being fully mixed with CO2 foam in the injection drilling foam fracturing crack 5 to form water-containing CO2 gas, it is displaced toward the target reservoir 4 through the wall surface of the injection drilling foam fracturing crack 5. Under the action of the pressure difference, the oil and gas in the target reservoir 4 gradually flows into the extraction drilling fracturing crack 6 and returns to the ground through the extraction borehole 2.

[0023] Example 2 The present embodiment provides a method for enhancing reservoir displacement and production by synergistic foam fracturing and gas injection, comprising the following steps: Step 1: See Figure 1 and Figure 3According to the permeability and ground stress parameters of the target reservoir 4, a fluid injection borehole 1 is drilled into the target reservoir 4 at the lower part of the formation 3, and a drainage borehole 2 is arranged on both sides of the fluid injection borehole 1, and casing cementing and perforation are carried out; along the direction of the minimum horizontal principal stress of the target reservoir 4, the fluid injection borehole 1 is drilled into the fluid injection borehole horizontal section 7, and the drainage borehole 2 is drilled into the drainage borehole horizontal section 8; and a drainage borehole horizontal section 8 is formed on both sides of the fluid injection borehole horizontal section 7.

[0024] Step 2: Inject CO2 foam fracturing fluid through the horizontal section 7 of the injection borehole to form a series of vertical minimum horizontal stress The foam fracturing cracks 9 in the horizontal section of the injection borehole are formed in the direction of the liquid injection borehole. When the foam fracturing cracks 9 in the horizontal section of the injection borehole reach the predetermined position, a proppant is mixed into the CO2 foam fluid and the foam fracturing cracks 9 in the horizontal section of the injection borehole are continuously injected. After the injection is completed, a local stress disturbance area 10 of the reservoir is caused and formed around the foam fracturing cracks 9 in the horizontal section of the injection borehole.

[0025] The fracturing of the horizontal section 8 of the extraction borehole adopts conventional water-based fracturing fluid to form multiple fracturing cracks 11 in the horizontal section of the extraction borehole and perform flowback; The distance between the foam fracturing cracks 9 in the horizontal section of the injection borehole and the fracturing cracks 11 in the horizontal section of the extraction borehole is greater than 1.2 times the thickness of the target reservoir 4, and the extended half-fracture length of the foam fracturing cracks 9 in the horizontal section of the injection borehole and the fracturing cracks 11 in the horizontal section of the extraction borehole is less than 3 / 4 of the distance between the injection borehole 1 and the extraction borehole 2.

[0026] The fracturing of the horizontal section 7 of the injection borehole and the horizontal section 8 of the extraction borehole adopts an alternating staged fracturing process, that is, the first section of the cracks in the horizontal section 7 of the injection borehole and the horizontal section 8 of the extraction borehole are formed by fracturing in sequence, and then the second section of the cracks in the horizontal section 7 of the injection borehole and the horizontal section 8 of the extraction borehole are fractured again, and the stress shadow effect of multiple fractures is used to avoid the convergence of multiple fractures, so as to realize the parallel expansion of multiple fractures in the horizontal well mode.

[0027] Step three: Inject CO2 gas into the horizontal section 7 of the injection borehole. After mixing with the CO2 foam fracturing fluid in the foam fracturing cracks 9 of the injection borehole to form saturated water CO2 gas, displace the target reservoir 4 matrix. Under the action of the pressure difference, the oil and gas in the target reservoir 4 gradually flow into the fracturing cracks 11 of the horizontal section of the extraction borehole, and return to the ground through the horizontal section 8 of the extraction borehole.

[0028] Example 3 The method of this embodiment is the same as that of Embodiment 1 except for the following differences. The difference is that in step 2, for strongly adsorbent reservoirs such as coal seams, it is not necessary to drill the extraction borehole 2. N2 foam fluid is used for fracturing the injection borehole 1, and N2 gas or flue gas with a high N2 content is subsequently injected to avoid the target reservoir 4 from adsorbing CO2 gas and expanding, resulting in a reduction in injection capacity. After the well is shut down for 60 to 120 days, the pressure of the injection borehole 1 is directly reduced for extraction.

[0029] Example 4 The method of this embodiment is the same as that of Embodiment 1 except for the following differences. The difference is that for the CO2 storage project in the hyperpermeable saline layer, a thickened CO2 foam fracturing fluid with 1-2% guar gum added can be used to perform injection drilling 1 fracturing, and then CO2 gas is injected for storage.

[0030] The above content is a further detailed description of the present invention in combination with a specific preferred embodiment. It cannot be determined that the specific embodiments of the present invention are limited to this. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the present invention, which should be regarded as belonging to the present invention and the scope of patent protection determined by the submitted claims.

Claims

1. A method for enhancing reservoir displacement and increasing production by synergistic foam fracturing and gas injection, characterized in that: The following steps are involved: Step 1: drilling a fluid injection borehole (1) and a drainage borehole (2) into the target reservoir (4); Step 2: injecting CO2 foam fluid into the injection borehole (1), pressurizing the injection borehole (1) to perform foam fracturing to form injection borehole foam fracturing cracks (5), and injecting fracturing fluid into the extraction borehole (2) to form extraction borehole fracturing cracks (6); Step 3: Inject CO2 gas into the injection borehole (1). After being fully mixed with the CO2 foam fluid in the injection borehole foam fracturing crack (5) to form water-containing CO2 gas, the CO2 gas is displaced toward the target reservoir (4) through the wall of the injection borehole foam fracturing crack (5). Under the action of the pressure difference, the oil and gas in the target reservoir (4) gradually flows into the extraction borehole fracturing crack (6) and returns to the ground through the extraction borehole (2).

2. A method for enhancing reservoir displacement and increasing production by synergistic foam fracturing and gas injection, characterized in that: The following steps are involved: Step 1: drilling a fluid injection borehole (1) and a drainage borehole (2) into the target reservoir (4); along the direction of the minimum horizontal principal stress of the target reservoir (4), the fluid injection borehole (1) is drilled into the horizontal section (7) of the fluid injection borehole, and the drainage borehole (2) is drilled into the horizontal section (8) of the drainage borehole; Step 2: Inject CO2 foam fluid through the horizontal section of the injection borehole (7) to form a series of vertical minimum horizontal ground stress A group of foam fracturing cracks (9) in the horizontal section of the injection borehole are formed in the direction of the injection direction; a local reservoir stress disturbance area (10) is formed around the foam fracturing cracks (9) in the horizontal section of the injection borehole; and a plurality of fracturing cracks (11) in the horizontal section of the extraction borehole are formed by injecting fracturing fluid into the horizontal section of the extraction borehole (8); Step 3: Inject CO2 gas into the horizontal section of the injection borehole (7), and form saturated water CO2 gas with CO2 foam fluid in the foam fracturing cracks (9) of the horizontal section of the injection borehole, and then displace the target reservoir (4) matrix. Under the action of pressure difference, oil and gas in the target reservoir (4) gradually flow into the fracturing cracks (11) of the horizontal section of the extraction borehole, and return to the ground through the horizontal section of the extraction borehole (8).

3. The method for enhancing reservoir displacement and increasing production by synergistic foam fracturing and gas injection according to claim 2, characterized in that: In step 3, the injection pressure of CO2 gas is lower than the minimum horizontal principal stress of the target reservoir (4).

4. The method for enhancing reservoir displacement and increasing production by synergistic foam fracturing and gas injection according to claim 1, characterized in that: In steps 2 and 3, the CO2 foam fluid is replaced by N2 or flue gas foam fluid, and in step 3, the CO2 gas is replaced by N2 or flue gas.

5. The method for enhancing reservoir displacement and increasing production by synergistic foam fracturing and gas injection according to claim 1, characterized in that: In step 1, the straight-line distance between the injection borehole (1) and the extraction borehole (2) is greater than 1.2 times the thickness of the target reservoir (4).

6. The method for enhancing reservoir displacement and increasing production by synergistic foam fracturing and gas injection according to claim 2, characterized in that: The distance between the foam fracturing cracks (9) in the horizontal section of the injection borehole and the fracturing cracks (11) in the horizontal section of the extraction borehole is greater than 1.2 times the thickness of the target reservoir (4), and the extended half-fracture length of the foam fracturing crack group (9) in the horizontal section of the injection borehole and the fracturing crack group (11) in the horizontal section of the extraction borehole is less than 3 / 4 of the distance between the injection borehole (1) and the extraction borehole (2).

7. The method for enhancing reservoir displacement and increasing production by synergistic foam fracturing and gas injection according to claim 2, characterized in that: The injection drilling hole (1) and the extraction drilling hole (2) adopt a multi-well sequential staged fracturing process to sequentially open the same section of fractures in different wells.

8. A method for enhancing reservoir displacement and increasing production by synergistic foam fracturing and gas injection according to claim 1 or 2, characterized in that: In step 2, when the target reservoir (4) is a highly adsorbent reservoir, the extraction borehole (2) is not drilled, and the injection borehole (1) is fractured using N2 foam fluid, followed by injection of N2 gas or flue gas. After the well is shut down for 60 days, the pressure of the injection borehole (1) is directly reduced for extraction.

9. The method for enhancing reservoir displacement and increasing production by synergistic foam fracturing and gas injection according to claim 1, characterized in that: When high permeability reservoir fracturing is required, a viscosity-enhancing CO2 foam fluid with 1-2% by mass of guar gum added is used for injection drilling (1) fracturing.

10. The method for enhancing reservoir displacement and increasing production by synergistic foam fracturing and gas injection according to claim 1, characterized in that: When the liquid injection drilling foam fracturing crack (5) reaches a predetermined position, a proppant is mixed into the CO2 foam fluid and the fluid is continuously injected into the liquid injection drilling foam fracturing crack (5).

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