Fracturing anti-gas-channeling fracture-forming design method for low-permeability reservoir CCUS producing well

Abstract

The invention belongs to the technical field of downhole operation fracturing in the petroleum industry, and discloses a low-permeability reservoir CCUS producing well fracturing gas channeling prevention fracture forming design method. The method comprises the steps that stratum parameters and well pattern parameters of a target well area are obtained; calculating the maximum sweep radius of the CO2 injection well by using the CO2 flooding minimum starting pressure gradient and the CO2 flooding injection-production pressure difference; determining the maximum artificial fracture half length of the oil producing well by using the maximum swept radius of the CO2 injection well and the injection-production well distance; s4, according to the maximum artificial fracture half length of the oil producing well, the fracturing optimization design software is used for simulating and calculating the corresponding fracturing displacement, the corresponding sand amount and the corresponding liquid amount; a soluble temporary plugging ball is added to temporarily plug holes in the direction of the artificial crack, so that the crack turns hard. According to the method, the production of the oil producing well in the CCUS process of the low-permeability reservoir is increased by 20%, meanwhile, under the existing fracturing scale, CO2 cannot be rapidly inrush, CO2 gas channeling is effectively prevented, and it is guaranteed that the production capacity of the CCUS oil producing well is exerted.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of fracturing in downhole operation in the petroleum industry, and is a design method for fracturing and anti-gas channeling and fracture creation in a CCUS oil production well of a low-permeability oil reservoir. BACKGROUND

[0002] Carbon capture, utilization and storage (CCUS) technology is a carbon reduction technology that has attracted much attention in recent years, that is, CO2 emitted in the production process is captured and purified, and then reused and stored in a new production process, which can directly reduce CO2 emissions. CCUS technology is an effective means to improve oil recovery in the process of oil production, which changes the physical and chemical properties of crude oil by injecting CO2, so that it is easier to be produced. For low-permeability oil reservoirs, the underground matrix has poor seepage capacity, and the crude oil cannot flow out naturally after drilling. The oil field often uses fracturing means to increase the reservoir reconstruction volume and then uses water injection to achieve the effect of increasing production, but this increases the cost of production and wastes a lot of water resources.

[0003] After water flooding, micro residual oil is mainly distributed in small pore throats and non-connected pores. The space for further improving the recovery rate by water flooding is small, and the cost is also high. If CCUS technology is used, liquid CO2 is injected into the reconstructed reservoir instead of water, so that CO2 and crude oil can be mixed to displace oil. After mixing, the interface disappears, CO2 can enter smaller pore throats, the starting pressure gradient of the oil displacement layer is reduced, and the oil layer that cannot be used by conventional water flooding can be effectively displaced, which can greatly improve the recovery rate of low-permeability oil reservoirs. CCUS technology not only can utilize fossil energy with low carbon, but also is an important way to implement the green and low-carbon development strategy of the petroleum industry.

[0004] However, during the CO2 injection process after fracturing and fracture creation in the oil production well, due to the low viscosity and large diffusion coefficient of liquid CO2, the swept area after injection is large, which is easy to cause gas channeling during the oil displacement utilization stage after fracturing in the oil production well, affect the injection-production relationship of the block, and cause ineffective circulation of CO2. If the oil production well only controls the length of the artificial fracture to achieve anti-gas channeling, it will lead to insufficient reservoir reconstruction and low production, and cannot achieve the purpose of fracturing and increasing production. Therefore, a technical method for fracturing and fracture creation, increasing production and considering anti-gas channeling is needed for CCUS oil production wells in low-permeability oil reservoirs. SUMMARY

[0005] In the prior art, due to poor seepage capacity of low-permeability oil reservoirs, a good displacement relationship cannot be established in a long period of time after CO2 injection in the CCUS process, and it is necessary to perform fracturing reconstruction before displacement to improve initial productivity and prevent serious gas channeling after gas injection, thereby affecting productivity. The purpose of the present application is to provide a fracturing anti-gas channeling fracture design method for a CCUS oil production well in a low-permeability oil reservoir, which on the one hand optimizes the fracturing technical route and individually designs the fracturing parameters by strengthening the understanding of the reservoir physical properties, well pattern conditions and reconstruction requirements of the target block, thereby improving the fracturing reconstruction effect; and on the other hand provides an effective displacement channel for subsequent CCUS gas injection, so as to realize the miscibility of CO2 and crude oil, avoid the ineffective circulation of CO2, and thereby improve the recovery efficiency of the low-permeability oil reservoir.

[0006] In order to realize the fracturing fracture creation, yield increase and gas channeling prevention of a CCUS oil production well in a low-permeability oil reservoir, the present application provides a fracturing anti-gas channeling fracture design method for a CCUS oil production well in a low-permeability oil reservoir, comprising the following steps:

[0007] Step S1, obtaining formation parameters and well pattern parameters of a target well area;

[0008] Step S2, calculating the maximum sweep radius of a CO2 injection well by using the minimum starting pressure gradient of CO2 flooding and the injection-production pressure difference of CO2 flooding;

[0009] Step S3, determining the maximum artificial fracture half-length of an oil production well by using the maximum sweep radius of the CO2 injection well and the injection-production well spacing;

[0010] Step S4, simulating and calculating the corresponding fracturing displacement, sand volume and liquid volume by using fracturing optimization design software according to the maximum artificial fracture half-length of the oil production well;

[0011] Step S5, adding soluble temporary plugging balls to temporarily plug the artificial fracture direction hole, so as to make the fracture hard to turn.

[0012] Further, the step S1 comprises: obtaining well pattern parameters of a target well area, the minimum starting pressure gradient of a CO2 flooding reservoir and the injection-production pressure difference of CO2 flooding;

[0013] Further, the step S2 comprises: calculating the maximum sweep radius of a CO2 injection well by using the minimum starting pressure gradient of CO2 flooding and the injection-production pressure difference of CO2 flooding;

[0014] The maximum sweep radius equation of the CO2 injection well is: In the formula, d is the maximum sweep radius of the CO2 injection well, m; ΔP is the injection-production pressure difference, MPa; G is the minimum starting pressure gradient of the CO2 flooding reservoir, MPa / m;

[0015] Further, the step S3 comprises: determining the maximum artificial fracture half-length of an oil production well by using the maximum sweep radius of a CO2 injection well and the injection-production well spacing;

[0016] Equation of the maximum artificial fracture half-length of the oil production well: x f = R-d, wherein x f is the maximum artificial fracture half-length of the oil production well, m; R is the injection-production well spacing, m; and d is the maximum sweep radius of the CO2 injection well, m.

[0017] Further, the step S4 comprises: calculating the primary fracturing fluid volume according to the maximum artificial fracture half-length of the oil production well.

[0018] Equation of the primary fracturing fluid volume: V1=2x f wh(1+η); wherein V1 is the primary fracturing fluid volume, m 3 ; x f is the maximum fracture half-length of the oil production well; w is the fracture zone width, m; h is the fracture height, m; and η is the fracturing fluid liquid efficiency, dimensionless.

[0019] Further, the step S5 comprises: adding soluble temporary plugging balls to temporarily plug the artificial fracture direction perforations, so as to make the fracture hard divert.

[0020] Equation of the soluble temporary plugging ball volume: wherein A is the soluble temporary plugging ball volume, pieces; and N is the number of perforations, pieces.

[0021] Compared with the prior art, the method has the beneficial effects that:

[0022] The method can increase the production of the oil production well by 20% in the CCUS process of the low-permeability reservoir, and can effectively prevent the rapid breakthrough of CO2 and the CO2 gas channeling under the existing fracturing scale, so as to guarantee the production capacity of the CCUS oil production well. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 It is a flow chart of a fracturing anti-gas channeling fracture design method for a CCUS oil production well in a low-permeability reservoir. DETAILED DESCRIPTION

[0024] In order to make the technical problems, technical solutions and advantages of the present application clearer, specific embodiments will be described in detail below, but the protection scope of the present application is not limited to the following description.

[0025] Example 1

[0026] The present application provides a fracturing anti-gas channeling fracture design method for a CCUS oil production well in a low-permeability reservoir, and the specific implementation process is as shown in Figure 1 , which comprises the following steps:

[0027] Step S1, taking the Gaotaizi oil layer of a block in the Daqingzi oilfield as an example, the block belongs to a large-diameter extended area, the well spacing is 450 m, the well row is 150 m, the reservoir permeability is 1 mD, the minimum starting pressure gradient of CO2 flooding is 0.05 MPa / m, and the injection-production pressure difference of CO2 flooding is 15 MPa;

[0028] Step S2, using the minimum starting pressure gradient of CO2 flooding of the block 0.05 MPa / m and the injection-production pressure difference of CO2 flooding 15 MPa, the maximum sweep radius of the CO2 injection well is calculated to be 300 m;

[0029] The maximum sweep radius equation of the CO2 injection well is: In the formula, d is the maximum sweep radius of the CO2 injection well, m; ΔP is the injection-production pressure difference, MPa; G is the minimum starting pressure gradient of the CO2 flooding reservoir, MPa / m;

[0030] Step S3, using the maximum sweep radius of the CO2 injection well of the block 300 m and the injection-production well spacing 450 m, the maximum artificial fracture half length of the production well is determined to be 150 m;

[0031] The maximum artificial fracture half length equation of the production well is x f =R-d, in which x f is the maximum artificial fracture half length of the production well, m; R is the injection-production well spacing, m; d is the maximum sweep radius of the CO2 injection well, m;

[0032] Step S4, according to the maximum artificial fracture half length of the production well of the block 150 m, using the fracturing optimization design software FracproPT to simulate the fracture zone width of the block 0.22 m, the fracture height 58 m, the fracturing fluid liquid efficiency 30%, the initial fracturing fluid volume is calculated to be 498 m 3 ;

[0033] The initial fracturing fluid volume equation is V1=2x f wh(1+η); in which V1 is the initial fracturing fluid volume, m 3 ; x f is the maximum fracture half length of the production well; w is the fracture zone width, m; h is the fracture height, m; η is the fracturing fluid liquid efficiency, dimensionless;

[0034] Step S5, the perforation layer section of the production well adopts spiral perforation, the hole density is 10 holes / m, the soluble temporary plugging ball is added to temporarily block the artificial fracture dominant direction hole, so as to make the fracture forced to turn, and the dosage of soluble temporary plugging ball per meter is 6.

[0035] The soluble temporary plugging ball dosage equation is: In the formula, A is the dosage of soluble temporary plugging ball, pieces; N is the number of perforation holes, pieces.

[0036] The above-described embodiments are merely preferred embodiments of the present application, but are not all the embodiments that can be implemented by the present application. Any obvious modifications made by those skilled in the art to the present application without departing from the principles and spirit of the present application should be considered to fall within the scope of protection of the claims of the present application.

Claims

1. A method for fracture diversion design of a CCUS production well in a low permeability reservoir, characterized in that, The method comprises the following steps: Step S1, obtaining formation parameters and well pattern parameters of a target well area; Step S2, calculating a maximum swept radius of a CO2 injection well by using a minimum starting pressure gradient of CO2 flooding and a CO2 injection-production pressure difference; Step S3, determining a maximum artificial fracture half-length of a production well by using the maximum swept radius of the CO2 injection well and an injection-production well spacing; Step S4, simulating and calculating a corresponding fracturing displacement, sand volume and liquid volume by using fracturing optimization design software according to the maximum artificial fracture half-length of the production well; Step S5, adding soluble temporary plugging balls to temporarily plug the artificial fracture direction hole, so as to make the fracture hard divert.

2. The method according to claim 1, wherein, Step S1 comprises: obtaining well pattern parameters of a target well area, a minimum starting pressure gradient of a CO2 flooding reservoir and a CO2 injection-production pressure difference.

3. The method according to claim 1, wherein, Step S2 comprises: calculating a maximum swept radius of a CO2 injection well by using a minimum starting pressure gradient of CO2 flooding and a CO2 injection-production pressure difference.

4. The method according to claim 3, wherein, The maximum swept radius of the CO2 injection well is calculated according to the following formula: where d is the maximum sweep radius of the CO2 injection well, m; ΔP is the injection-production pressure difference, MPa; G is the minimum starting pressure gradient of the CO2 flooding reservoir, MPa / m.

5. The low permeability reservoir CCUS production well fracture conformance design method of claim 1, wherein, Step S3 comprises: determining a maximum artificial fracture half-length of a production well by using the maximum swept radius of a CO2 injection well and an injection-production well spacing.

6. The method according to claim 5, wherein, The maximum artificial fracture half-length of the production well is calculated according to the following formula: x f = R - d, where x f is the maximum artificial fracture half-length of the production well, m; R is the injection-production well spacing, m; and d is the maximum sweep radius of the CO2 injection well, m.

7. The low permeability reservoir CCUS production well fracture conformance design method of claim 1, wherein, Step S4 comprises: calculating a primary fracturing liquid volume according to the maximum artificial fracture half-length of the production well.

8. The method according to claim 7, wherein, The primary fracturing liquid volume is calculated according to the following formula: V1 = 2x f wh(1 + η); where V1 is the primary fracturing fluid volume, m 3 ; x f is the maximum fracture half-length of the production well; w is the fracture zone width, m; h is the fracture height, m; η is a fracturing fluid liquid efficiency, dimensionless.

9. The low permeability reservoir CCUS production well fracture conformance design method of claim 1, wherein, Step S5 comprises: adding soluble temporary plugging balls to temporarily plug the artificial fracture direction hole, so as to make the fracture hard divert.

10. The low permeability reservoir CCUS production well fracture conformance creation design method of claim 1, wherein, The soluble temporary plugging ball dosage equation is calculated according to the following formula: In the formula, A is the amount of soluble temporary plugging balls, pieces; N is the number of perforation holes, pieces.

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