A comprehensive evaluation method for the self-steering acid-acidification steering effect

Abstract

This invention discloses a comprehensive evaluation method for the self-directing acid-acidification diversion effect, relating to the field of carbonate reservoir stimulation technology, including the following steps: (1) using a dual-core flow device to conduct experiments on cores with different permeability ranges n, and measuring the self-directing acid-acidification diversion pressure and matrix permeability change rate; (2) using an acid-etched fracture conductivity device to measure the self-directing acid-acidification diversion pressure P under different closure pressures P c Experiments were conducted on the rock slab to measure the conductivity and roughness of the self-directing acid etching cracks; (3) The measured self-directing acid redirection pressure, matrix permeability change rate, self-directing acid etching crack conductivity and roughness were regressed and fitted to obtain comprehensive evaluation parameters of acidification redirection effect; This invention realizes a comprehensive and accurate evaluation and analysis of the self-directing acidification redirection effect of the carbonate rock block.

Description

Technical Field

[0001] This invention relates to the field of carbonate reservoir stimulation technology, specifically to a comprehensive evaluation method for the effect of self-directing acidification. Background Technology

[0002] Self-directing acid, as one of the main acid systems used for carbonate reservoir stimulation, is mainly composed of hydrochloric acid, a redirecting agent, a corrosion inhibitor, a corrosion inhibitor synergist, an iron ion stabilizer, and water. When it reacts with carbonate rocks, it continuously increases the viscosity of the liquid, blocking high-permeability reservoirs and allowing subsequent acid to redirect and stimulate low-permeability reservoirs.

[0003] The effectiveness of self-directing acid in the stimulation of carbonate reservoirs determines the production level of the implemented well. Currently, there are many parameters to characterize its acidizing and redirecting effect. Existing evaluation methods mainly use relatively single parameters to characterize the acidizing and redirecting effect of self-directing acid, which cannot take into account the redirecting properties of the self-directing acid itself and the characteristics of the acid etching fractures formed, and cannot comprehensively and accurately characterize the acidizing and redirecting effect of self-directing acid. Summary of the Invention

[0004] This invention aims to address the technical problem that existing evaluation methods cannot comprehensively and accurately characterize the self-directing acidizing effect. The purpose is to provide a comprehensive evaluation method for the self-directing acidizing effect, which can more comprehensively and accurately characterize the self-directing acidizing effect and is suitable for evaluating the self-directing acidizing effect of carbonate rocks with different strata, reservoir pressures, and temperatures.

[0005] This invention is achieved through the following technical solution:

[0006] A comprehensive evaluation method for the self-steering acid-oxidizing steering effect includes the following steps:

[0007] (1) The initial permeability K1 and K2 of low-permeability and high-permeability cores were determined by using a dual-core flow device with standard brine, and the pressure P1 at the K1 value was recorded. The high-permeability core was then plugged with a self-directing acid system. The turning pressure P2 was determined based on the highest point of the time-pressure change curve. After the core was broken through, the permeability K3 of the low-permeability core after acidification was determined by using the same discharge volume of standard brine. The permeability change rate C = (K3-K1) / K1 was calculated.

[0008] (2) Experiments were conducted using cores with different permeability ranges n. Step (1) was repeated. Based on the fitting regression curves of the permeability change rate C, the permeability range n, and the dimensionless pressure P2 / P1, the correlation coefficient between C and f(P2 / P1, n) was determined.

[0009] (3) Using an acid-etched crack conductivity device, the conductivity D1 under a set closing pressure was measured. The conductivity D2 of the acid-etched crack was measured under the same discharge rate and excess self-directing acid system. The rock slab before and after acid etching was scanned to obtain the surface area A1 before acid etching and the surface area A2 after acid etching. The roughness S of the acid-etched crack was calculated as A1 / A2.

[0010] (4) Using different closing pressures P c Experiments were conducted on the rock slab, repeating step (3), based on the dimensionless closure pressure P. c The fitted regression curves of / 10 with dimensionless conductivity D2 / D1 and roughness S determine the relationship between D2 / D1 and f(S, P). c The correlation coefficient of the relationship / 10);

[0011] (5) Obtain the comprehensive evaluation parameter M for the self-steering acidification steering effect: M = f(P2 / P1, n) + f(S, P c / 10).

[0012] The self-directing acidification and acidification effect evaluation method provided by this invention takes into account both the acidification effect of the self-directing acid itself and the effectiveness of the formed acid etching cracks. By regressing and fitting the measured self-directing acidification pressure, matrix permeability change rate, acid etching crack conductivity and crack roughness, comprehensive evaluation parameters of acidification and acidification effect are obtained, which can realize a comprehensive and accurate evaluation and analysis of the self-directing acidification and acidification effect of carbonate rocks in the block.

[0013] As a further technical solution of the present invention, the core is a marble core or a reservoir core, the core length is greater than or equal to 1.5 times the diameter, and the permeability ratio difference between the high-permeability core and the low-permeability core is 1-50.

[0014] As a further technical solution of the present invention, the self-directing acid system includes the following components: self-directing agent, corrosion inhibitor, corrosion inhibitor synergist, iron ion stabilizer, hydrochloric acid, and the balance being water.

[0015] As a further technical solution of the present invention, the self-reversing acid system comprises, by mass percentage, the following components: 6-8% self-reversing agent, 3% corrosion inhibitor, 1% corrosion inhibitor synergist, 2% iron ion stabilizer, 20% hydrochloric acid, and the balance being water.

[0016] As a further technical solution of the present invention, the permeability range n can take values ​​of 10, 20, 30, 40 and 50.

[0017] As a further technical solution of the present invention, the rock slab is a marble rock slab or a reservoir rock slab, and the core length is greater than or equal to 3 times the diameter.

[0018] As a further technical solution of the present invention, the closing pressure P c The values ​​include 10MPa, 20MPa, 30MPa, 40MPa, 50MPa and 60MPa.

[0019] As a further technical solution of the present invention, the relationship between C, P2 / P1, and n is: C = a(P2 / P1) 2 +bn+d;

[0020] Where a, b, and d are correlation coefficients.

[0021] As a further technical solution of the present invention, D2 / D1 and S, P c The relationship is: D2 / D1 = eS 2 +gln(P c / 10)+h;

[0022] Where e, g, and h are correlation coefficients.

[0023] As a further technical solution of the present invention, the comprehensive evaluation parameter for the self-steering acid-oxidizing steering effect is M = a(P2 / P1). 2 +bn+d+eS 2 +gln(P c / 10)+h.

[0024] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0025] 1. The comprehensive evaluation method for the acidification effect of self-directing acidification provided by this invention takes into account both the acidification effect of the self-directing acid itself and the effectiveness of the formed acid etching cracks. By regression fitting of the measured self-directing acidification pressure, matrix permeability change rate, acid etching crack conductivity and crack roughness, comprehensive evaluation parameters for acidification effect are obtained, which can realize a comprehensive and accurate evaluation and analysis of the acidification effect of self-directing acidification in the carbonate rocks of the block.

[0026] 2. The self-directing acidizing diversion effect comprehensive evaluation method provided by the present invention comprehensively considers factors such as diversion pressure, permeability change, conductivity and acid-etched fracture roughness. Among them, the two parameters of diversion pressure and permeability change indicate the effective transformation of low-permeability reservoirs, while the two parameters of conductivity and acid-etched fracture roughness indicate the connectivity and flow capacity of fractures, which can more comprehensively and accurately characterize the self-directing acidizing diversion effect.

[0027] 3. The self-directing acidizing and acidizing reversal effect comprehensive evaluation method provided by the present invention can directly calculate the comprehensive evaluation parameter M of the acidizing and reversal effect when the carbonate reservoir characteristics are similar in the same block, without the need to measure all parameters, which can improve the evaluation efficiency.

[0028] 4. The comprehensive evaluation method for the self-directing acidizing effect provided by the present invention is suitable for evaluating the self-directing acidizing effect of carbonate rocks with different strata, reservoir pressures and temperatures. Attached Figure Description

[0029] To more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of the present invention and should not be considered as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort. In the drawings:

[0030] Figure 1 This is the permeability change rate and permeability range, dimensionless pressure relationship curve of Embodiment 1 of the present invention;

[0031] Figure 2 This is the curve showing the relationship between dimensionless flow conduction capacity and dimensional closure pressure and roughness in Embodiment 1 of the present invention;

[0032] Figure 3 This is the permeability change rate and permeability range, dimensionless pressure relationship curve of Embodiment 2 of the present invention;

[0033] Figure 4 This is the curve showing the relationship between dimensionless flow capacity and dimensional closing pressure and roughness in Embodiment 2 of the present invention. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments and accompanying drawings. The illustrative embodiments and descriptions of the present invention are only used to explain the present invention and are not intended to limit the present invention.

[0035] In the following description, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be apparent to those skilled in the art that these specific details are not necessary to practice the invention. In other embodiments, well-known structures, circuits, materials, or methods have not been specifically described in order to avoid obscuring the invention.

[0036] This invention provides a method for comprehensively evaluating the self-steering acid-oxidizing steering effect, comprising the following steps:

[0037] (1) The initial permeability K1 and K2 of low-permeability and high-permeability cores were determined by using a dual-core flow device with standard brine, and the pressure P1 at the K1 value was recorded. The high-permeability core was then plugged with a self-directing acid system. The turning pressure P2 was determined based on the highest point of the time-pressure change curve. After the core was broken through, the permeability K3 of the low-permeability core after acidification was determined by using the same discharge volume of standard brine. The permeability change rate C = (K3-K1) / K1 was calculated.

[0038] (2) Experiments were conducted using cores with different permeability ranges n. Step (1) was repeated. Based on the fitting regression curves of the permeability change rate C, the permeability range n, and the dimensionless pressure P2 / P1, the correlation coefficient between C and f(P2 / P1, n) was determined.

[0039] (3) Using an acid-etched crack conductivity device, the conductivity D1 under a set closing pressure was measured. The conductivity D2 of the acid-etched crack was measured under the same discharge rate and excess self-directing acid system. The rock slab before and after acid etching was scanned to obtain the surface area A1 before acid etching and the surface area A2 after acid etching. The roughness S of the acid-etched crack was calculated as A1 / A2.

[0040] (4) Using different closing pressures P c Experiments were conducted on the rock slab, repeating step (3), based on the dimensionless closure pressure P. c The fitted regression curves of / 10 with dimensionless conductivity D2 / D1 and roughness S are used to determine the relationship between D2 / D1 and f(S, P). c The correlation coefficient of the relationship / 10);

[0041] (5) Obtain the comprehensive evaluation parameter M for the self-steering acidification steering effect: M = f(P2 / P1, n) + f(S, P c / 10).

[0042] The self-directing acidizing diversion effect evaluation method provided by this invention comprehensively considers factors such as diversion pressure, permeability change, conductivity, and acid-etched fracture roughness. Among them, the two parameters of diversion pressure and permeability change indicate the effective transformation of low-permeability reservoirs, while the two parameters of conductivity and acid-etched fracture roughness indicate the connectivity and flow capacity of fractures, which can more comprehensively and accurately characterize the self-directing acidizing diversion effect.

[0043] As a further technical solution of the present invention, the core is a marble core or a reservoir core, the core length is greater than or equal to 1.5 times the diameter, and the permeability ratio difference between the high-permeability core and the low-permeability core is 1-50.

[0044] As a further technical solution of the present invention, the self-directing acid system includes the following components: self-directing agent, corrosion inhibitor, corrosion inhibitor synergist, iron ion stabilizer, hydrochloric acid, and the balance being water.

[0045] As a further technical solution of the present invention, the self-reversing acid system comprises, by mass percentage, the following components: 6-8% self-reversing agent, 3% corrosion inhibitor, 1% corrosion inhibitor synergist, 2% iron ion stabilizer, 20% hydrochloric acid, and the balance being water.

[0046] As a further technical solution of the present invention, the permeability range n can take values ​​of 10, 20, 30, 40 and 50.

[0047] As a further technical solution of the present invention, the rock slab is a marble rock slab or a reservoir rock slab, and the core length is greater than or equal to 3 times the diameter.

[0048] As a further technical solution of the present invention, the closing pressure P c The values ​​include 10MPa, 20MPa, 30MPa, 40MPa, 50MPa and 60MPa.

[0049] Using the above method, the relationship between C, P2 / P1, and n is obtained as: C = a(P2 / P1) 2 +bn+d; where a, b, and d are the correlation coefficients.

[0050] The D2 / D1 and S, P c The relationship is: D2 / D1 = eS 2 +gln(P c / 10)+h; where e, g, and h are correlation coefficients.

[0051] Thus, the comprehensive evaluation parameter for the self-steering acid-oxidizing steering effect is obtained as M = a(P2 / P1). 2 +bn+d+eS 2 +gln(P c / 10)+h.

[0052] The following are specific embodiments of the present invention.

[0053] Example 1

[0054] This embodiment uses cores and slabs from Block A for experiments. The formula for the self-directing acid is: 6% self-directing agent, 3% corrosion inhibitor, 1% corrosion inhibitor synergist, 2% iron ion stabilizer, 20% hydrochloric acid, and the balance being water.

[0055] A comprehensive evaluation method for the self-steering acid-oxidizing steering effect includes the following steps:

[0056] (1) Using a dual-core flow apparatus, experiments were conducted on core samples with different permeability ranges n (10, 20, 30, 40, 50). The initial permeability of the low-permeability core was determined using standard brine, K1, and the pressure P1 at K1 was recorded. Then, a self-directing acid system was used to plug the high-permeability core. The redirecting pressure P2 was determined based on the highest point of the time-pressure change curve. After the core was breached, the permeability K3 of the low-permeability core after acidification was determined using the same flow rate of standard brine. The permeability change rate C = (K3 - K1) / K1 was calculated. The results are shown in Table 1. Figure 1 This is the curve showing the relationship between the rate of change of permeability and the permeability range, and the dimensionless pressure in this embodiment.

[0057] Table 1. Experimental data on changes in pressure and permeability of self-directing acid diversion.

[0058] n <![CDATA[K1(mD)]]> <![CDATA[P2(MPa)]]> <![CDATA[P2 / P1 (dimensionless)]]> <![CDATA[K3(mD)]]> C 10 0.5403 5.8 0.98 0.7492 0.39 20 0.3861 6.3 1.02 0.5578 0.44 30 0.2631 8.9 1.09 0.3899 0.48 40 0.1729 10.9 1.19 0.2776 0.61 50 0.1331 15.3 1.37 0.2231 0.67

[0059] (2) Based on the fitting regression curves of the permeability change rate C and permeability range n, and dimensionless pressure P2 / P1 in Table 1, the relationship between C and f(P2 / P1, n) can be obtained as follows:

[0060] C = 0.27(P2 / P1) 2 +0.003n+0.1.

[0061] (3) Using an acid-etched crack flow-guiding device, under different closing pressures P c Experiments were conducted on the rock slab to measure the conductivity D1 under closure pressures of 10 MPa, 20 MPa, 30 MPa, 40 MPa, 50 MPa, and 60 MPa. The conductivity D2 of the acid-etched fractures was measured under the same displacement and excess self-rotating acid system. The rock slabs were scanned before and after acid etching to obtain the surface area A1 before etching and the surface area A2 after etching. The roughness S of the acid-etched fractures was calculated as S = A1 / A2. The results are recorded in Table 2. Figure 2 This is the curve showing the relationship between the dimensionless flow capacity and the dimensional closing pressure and roughness in this embodiment.

[0062] Table 2. Experimental data on self-directing acid conductivity and roughness.

[0063] <![CDATA[P c / 10 (dimensionless)]]> <![CDATA[D2(D·cm)]]> <![CDATA[D2 / D1 (dimensionless)]]> S (dimensionless) 2 248.6 0.67 0.43 3 169.3 0.44 0.31 4 112.4 0.29 0.24 5 51.7 0.13 0.21 6 23.5 0.07 0.2

[0064] (4) According to the dimensionless closure pressure P in Table 2 c The fitted regression curves of / 10 with dimensionless conductivity D2 / D1 and roughness S yield the relationship between D2 / D1 and f(S, P) c The relation is:

[0065] D2 / D1 = 33S 2 -0.78ln(P c / 10)+0.15.

[0066] (5) Obtain comprehensive evaluation parameters for the self-direction and acidification-direction effect of carbonate rocks in Block A:

[0067] M = 0.27(P2 / P1) 2 +0.003n+33S 2 -0.78ln(P c / 10)+0.25.

[0068] Example 2

[0069] This embodiment uses cores and slabs from Block B for experiments. The formula for the self-directing acid is: 8% self-directing agent, 3% corrosion inhibitor, 1% corrosion inhibitor synergist, 2% iron ion stabilizer, 20% hydrochloric acid, and the balance being water.

[0070] A comprehensive evaluation method for the self-steering acid-oxidizing steering effect includes the following steps:

[0071] (1) Using a dual-core flow apparatus, experiments were conducted on core samples with different permeability ranges n (10, 20, 30, 40, 50). The initial permeability of the low-permeability core was determined using standard brine, K1, and the pressure P1 at K1 was recorded. Then, a self-directing acid system was used to plug the high-permeability core. The redirection pressure P2 was determined based on the highest point of the time-pressure change curve. After the core was breached, the permeability K3 of the low-permeability core after acidification was determined using the same flow rate of standard brine. The permeability change rate C = (K3 - K1) / K1 was calculated. The results are shown in Table 3. Figure 3 This is the curve showing the relationship between the rate of change of permeability and the permeability range, and the dimensionless pressure in this embodiment.

[0072] Table 3. Experimental data on changes in pressure and permeability of self-directing acid diversion.

[0073] n <![CDATA[K1(mD)]]> <![CDATA[P2(MPa)]]> <![CDATA[P2 / P1 (dimensionless)]]> <![CDATA[K3(mD)]]> C 10 0.6202 6.5 1.21 0.8836 0.42 20 0.4261 7.7 1.24 0.621 0.46 30 0.3085 9.1 1.25 0.4713 0.53 40 0.2229 11.9 1.29 0.3576 0.61 50 0.1543 16.6 1.48 0.2545 0.65

[0074] (2) Based on the fitting regression curves of the permeability change rate C, permeability range n, and dimensionless pressure P2 / P1 in Table 3, the relationship between C and f(P2 / P1, n) can be obtained as follows:

[0075] C = 2(P2 / P1) 2 -0.012n-3.13.

[0076] (3) Using an acid-etched crack flow-guiding device, under different closing pressures P cExperiments were conducted on the rock slab to measure the conductivity D1 under closure pressures of 10 MPa, 20 MPa, 30 MPa, 40 MPa, 50 MPa, and 60 MPa. The conductivity D2 of the acid-etched fractures was measured under the same displacement and excess self-directing acid system. The rock slabs were scanned before and after acid etching to obtain the surface area A1 before etching and the surface area A2 after etching. The roughness S of the acid-etched fractures was calculated as S = A1 / A2. The results are recorded in Table 4. Figure 4 This is the curve showing the relationship between the dimensionless flow capacity and the dimensional closing pressure and roughness in this embodiment.

[0077] Table 4. Experimental data on self-directing acid conductivity and roughness.

[0078]

[0079]

[0080] (4) According to the dimensionless closure pressure P in Table 2 c The fitted regression curves of / 10 with dimensionless conductivity D2 / D1 and roughness S yield the relationship between D2 / D1 and f(S, P) c The relation is:

[0081] D2 / D1 = 0.32S 2 -0.08ln(P c / 10)+0.18.

[0082] (5) Obtain comprehensive evaluation parameters for the self-direction and acidification-direction effect of carbonate rocks in Block B:

[0083] M = 2(P2 / P1) 2 -0.012n+0.32S 2 -0.08ln(P c / 10)-2.95.

[0084] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A comprehensive evaluation method for the self-steering acidification steering effect, characterized in that, Includes the following steps: (1) The initial permeability K1 and K2 of low-permeability and high-permeability cores were determined by using a dual-core flow device with standard brine, and the pressure P1 at the K1 value was recorded. The high-permeability core was then plugged with a self-directing acid system. The turning pressure P2 was determined based on the highest point of the time-pressure change curve. After the core was broken through, the permeability K3 of the low-permeability core after acidification was determined by using the same discharge volume of standard brine. The permeability change rate C = (K3-K1) / K1 was calculated. (2) Experiments were conducted using cores with different permeability ranges n. Step (1) was repeated. Based on the fitting regression curves of the permeability change rate C, the permeability range n, and the dimensionless pressure P2 / P1, the correlation coefficient between C and f(P2 / P1, n) was determined. (3) Using an acid-etched crack conductivity device, the conductivity D1 under a set closing pressure was measured. The conductivity D2 of the acid-etched crack was measured under the same discharge rate and excess self-directing acid system. The rock slab before and after acid etching was scanned to obtain the surface area A1 before acid etching and the surface area A2 after acid etching. The roughness S of the acid-etched crack was calculated as A1 / A2. (4) Using different closing pressures P c Experiments were conducted on the rock slab, repeating step (3), based on the dimensionless closure pressure P. c The fitted regression curves of / 10 with dimensionless conductivity D2 / D1 and roughness S determine the relationship between D2 / D1 and f(S, P). c The correlation coefficient of the relationship / 10); (5) Obtain the comprehensive evaluation parameter M for the self-steering acidification steering effect: M = f(P2 / P1, n) + f(S, P c / 10).

2. The method for comprehensively evaluating the self-steering acidification steering effect according to claim 1, characterized in that, The core sample is a marble core or a reservoir core, with a core length greater than or equal to 1.5 times the diameter, and the permeability ratio difference between high-permeability cores and low-permeability cores is 1-50.

3. The method for comprehensively evaluating the self-steering acidification steering effect according to claim 1, characterized in that, The self-reversing acid system comprises the following components: self-reversing agent, corrosion inhibitor, corrosion inhibitor synergist, iron ion stabilizer, hydrochloric acid, and the balance being water.

4. The method for comprehensively evaluating the self-steering acidification steering effect according to claim 3, characterized in that, The self-reversing acid system comprises, by mass percentage, the following components: 6-8% self-reversing agent, 3% corrosion inhibitor, 1% corrosion inhibitor synergist, 2% iron ion stabilizer, 20% hydrochloric acid, and the balance being water.

5. The method for comprehensively evaluating the self-steering acidification steering effect according to claim 1, characterized in that, The permeability range n can take values ​​of 10, 20, 30, 40, and 50.

6. The method for comprehensively evaluating the self-steering acidification steering effect according to claim 1, characterized in that, The rock slab is a marble rock slab or a reservoir rock slab, and the core length is greater than or equal to 3 times the diameter.

7. The method for comprehensively evaluating the self-steering acidification steering effect according to claim 1, characterized in that, The closing pressure P c The values ​​include 10MPa, 20MPa, 30MPa, 40MPa, 50MPa and 60MPa.

8. The method for comprehensively evaluating the self-steering acidification steering effect according to claim 1, characterized in that, The relationship between C, P2 / P1, and n is: C = a(P2 / P1) 2 +bn+d; Where a, b, and d are correlation coefficients.

9. The method for comprehensively evaluating the self-steering acidification steering effect according to claim 8, characterized in that, The D2 / D1 and S, P c The relationship is: D2 / D1 = eS 2 +gln(P c / 10)+h; Where e, g, and h are correlation coefficients.

10. A comprehensive evaluation method for the self-steering acidification steering effect according to claim 9, characterized in that, The comprehensive evaluation parameter for the self-steering acid-oxidizing steering effect is M = a(P2 / P1). 2 +bn+d+eS 2 +gln(P c / 10)+h.

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