Comprehensive evaluation method for acidification diverting effect of self-diverting acid

Abstract

The invention discloses a comprehensive evaluation method for the acidification diverting effect of self-diverting acid, and relates to the technical field of carbonate reservoir transformation, and the method comprises the following steps: (1) adopting a double-core flowing device to carry out experiments on cores with different permeability ranges n, and measuring to obtain the diverting pressure of the self-diverting acid and the change rate of matrix permeability; (2) adopting an acid etching fracture conductivity device to carry out experiments on the rock plate under different closing pressures Pc, and measuring to obtain the self-diverting acid etching fracture conductivity and fracture roughness; (3) performing regression fitting on the measured self-diverting acid diverting pressure, the measured matrix permeability change rate, the self-diverting acid etching fracture conductivity and the fracture roughness to obtain comprehensive evaluation parameters of the acidification diverting effect; according to the method, comprehensive and accurate evaluation analysis on the acidification diverting effect of the self-diverting acid of the block carbonate rock is realized.

Description

Technical Field

[0001] The invention relates to the technical field of carbonate reservoir transformation, and in particular to a comprehensive evaluation method for a self-steering acidizing diversion effect. Background Art

[0002] Self-diverting acid is one of the main acid systems used for carbonate reservoir transformation. It is mainly composed of hydrochloric acid, diverting agent, corrosion inhibitor, corrosion inhibitor enhancer, iron ion stabilizer and water. It can increase the viscosity of the liquid continuously when reacting with carbonate rock, thereby blocking high permeability reservoirs and diverting subsequent acid to transform low permeability reservoirs.

[0003] The effect of self-diverting acid on the transformation of carbonate reservoirs determines the production level of the implemented well. At present, there are many parameters to characterize the acidizing diversion effect. The existing evaluation methods mainly use a relatively single parameter to characterize the acidizing diversion effect of self-diverting acid. It is unable to take into account the diversion properties of the self-diverting acid itself and the characteristics of the acid-etched cracks formed, and it is unable to comprehensively and accurately characterize the acidizing diversion effect of self-diverting acid. Summary of the invention

[0004] The present invention aims to solve the technical problem that the existing evaluation methods cannot comprehensively and accurately characterize the steering effect of self-steering acid acidizing. The present invention aims to provide a comprehensive evaluation method for the steering effect of self-steering acid acidizing, which can more comprehensively and accurately characterize the steering effect of self-steering acid acidizing and is suitable for the evaluation of the steering effect of self-steering acid acidizing of carbonate rocks in different layers, different reservoir pressures and temperatures.

[0005] The present invention is achieved through the following technical solutions:

[0006] A method for comprehensively evaluating the steering effect of self-steering acidification includes the following steps:

[0007] (1) Using a dual core flow device, the initial permeabilities K1 and K2 of low-permeability and high-permeability cores were measured with standard brine, and the pressure P1 at the K1 value was recorded. The high-permeability core was then plugged with a self-steering acid system, and the steering 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 measured with the same displacement of standard brine, and the permeability change rate C = (K3-K1) / K1 was calculated;

[0008] (2) Conducting experiments with cores with different permeability extreme differences n, repeating step (1), and determining the correlation coefficient between C and f(P2 / P1, n) based on the fitted regression curve of the permeability change rate C, the permeability extreme difference n, and the dimensionless pressure P2 / P1;

[0009] (3) The conductivity of the acid-etched fractures is measured by using an acid-etched fracture conductivity device at a set closing pressure, D1. The conductivity of the acid-etched fractures measured under the same displacement and excess self-diverting acid system is D2. The rock plate before and after acid etching is scanned to obtain the surface area A1 before acid etching and the surface area A2 after acid etching. The roughness of the acid-etched fracture is calculated to be S=A1 / A2;

[0010] (4) Using different closing pressures P c Experiments were conducted on the rock plate, and step (3) was repeated. Based on the dimensionless closing pressure P c / 10 and the dimensionless conductivity D2 / D1, roughness S fitting regression curve, determine D2 / D1 and f(S, P c / 10) correlation coefficient;

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

[0012] The comprehensive evaluation method for the diversion effect of self-diverting acid acidizing provided by the present invention takes into account both the diversion effect of the self-diverting acid itself and the effectiveness of the formed acid-etched cracks, and regresses and fits the measured diversion pressure of the self-diverting acid, the rate of change of matrix permeability, and the conductivity and roughness of the self-diverting acid-etched cracks to obtain comprehensive evaluation parameters of the acidizing diversion effect, thereby realizing a comprehensive and accurate evaluation and analysis of the diversion effect of self-diverting acid acidizing 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 multiple 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-diverting acid system comprises the following components: a self-diverting agent, a corrosion inhibitor, a corrosion inhibitor synergist, an iron ion stabilizer, hydrochloric acid and the balance of water.

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

[0016] As a further technical solution of the present invention, the permeability range n includes 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] Among them, a, b, and d are correlation coefficients.

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

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

[0023] As a further technical solution of the present invention, the self-steering acidification steering effect comprehensive evaluation parameter 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 diversion effect of self-diverting acid acidizing provided by the present invention takes into account both the diversion effect of the self-diverting acid itself and the effectiveness of the formed acid-etched cracks. The measured diversion pressure of the self-diverting acid, the change rate of the matrix permeability, the conductivity of the self-diverting acid-etched cracks and the roughness of the cracks are regressed and fitted to obtain the comprehensive evaluation parameters of the acidizing diversion effect, which can realize a comprehensive and accurate evaluation and analysis of the diversion effect of self-diverting acid acidizing of carbonate rocks in the block.

[0026] 2. The comprehensive evaluation method for the steering effect of self-steering acid acidizing provided by the present invention comprehensively considers factors such as steering pressure, permeability change, conductivity and acid-etched fracture roughness. Among them, the two parameters of steering 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 steering effect of self-steering acid acidizing.

[0027] 3. The self-steering acidizing diversion effect comprehensive evaluation method provided by the present invention can be directly calculated according to the acidizing diversion effect comprehensive evaluation parameter M formula when the carbonate reservoir characteristics are similar in the same block, without the need to measure all parameters, thereby improving the evaluation efficiency.

[0028] 4. The comprehensive evaluation method for the diversion effect of self-diverting acid acidizing provided by the present invention is suitable for the evaluation of the diversion effect of self-diverting acid acidizing of carbonate rocks in different layers, different reservoir pressures and temperatures. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and should not be regarded as limiting the scope. For those of ordinary skill in the art, other relevant drawings can be obtained based on these drawings without creative work. In the drawings:

[0030] Figure 1 The relationship curve between the permeability change rate, the permeability extreme difference and the dimensionless pressure of Example 1 of the present invention;

[0031] Figure 2 is a relationship curve between dimensionless flow conductivity, dimensional closure pressure and roughness of Example 1 of the present invention;

[0032] Figure 3 The relationship curve between the permeability change rate, the permeability extreme difference and the dimensionless pressure of Example 2 of the present invention;

[0033] Figure 4 This is a relationship curve between the dimensionless flow conductivity and the dimensional closure pressure and roughness of Example 2 of the present invention. DETAILED DESCRIPTION

[0034] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments and drawings. The exemplary embodiments of the present invention and their description are only used to explain the present invention and are not intended to limit the present invention.

[0035] In the following description, a large number of specific details are set forth in order to provide a thorough understanding of the present invention. However, it is apparent to one of ordinary skill in the art that these specific details are not necessarily employed to practice the present invention. In other embodiments, in order to avoid obscuring the present invention, well-known structures, circuits, materials, or methods are not specifically described.

[0036] The present invention provides a method for comprehensively evaluating the steering effect of self-steering acidification, comprising the following steps:

[0037] (1) Using a dual core flow device, the initial permeabilities K1 and K2 of low-permeability and high-permeability cores were measured with standard brine, and the pressure P1 at the K1 value was recorded. The high-permeability core was then plugged with a self-steering acid system, and the steering 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 measured with the same displacement of standard brine, and the permeability change rate C = (K3-K1) / K1 was calculated;

[0038] (2) Conducting experiments with cores with different permeability extreme differences n, repeating step (1), and determining the correlation coefficient between C and f(P2 / P1, n) based on the fitted regression curve of the permeability change rate C, the permeability extreme difference n, and the dimensionless pressure P2 / P1;

[0039] (3) The conductivity of the acid-etched fractures is measured by using an acid-etched fracture conductivity device at a set closing pressure, D1. The conductivity of the acid-etched fractures measured under the same displacement and excess self-diverting acid system is D2. The rock plate before and after acid etching is scanned to obtain the surface area A1 before acid etching and the surface area A2 after acid etching. The roughness of the acid-etched fracture is calculated to be S=A1 / A2;

[0040] (4) Using different closing pressures P c Experiments were conducted on the rock plate, and step (3) was repeated. Based on the dimensionless closing pressure P c / 10 and the dimensionless conductivity D2 / D1, roughness S fitting regression curve, determine D2 / D1 and f(S, P c / 10) correlation coefficient;

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

[0042] The comprehensive evaluation method for the steering effect of self-steering acidizing provided by the present invention comprehensively considers factors such as steering pressure, permeability change, conductivity and acid-etched fracture roughness, among which the two parameters of steering 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 connected flow capacity of fractures, which can more comprehensively and accurately characterize the steering effect of self-steering acidizing.

[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 multiple 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-diverting acid system comprises the following components: a self-diverting agent, a corrosion inhibitor, a corrosion inhibitor synergist, an iron ion stabilizer, hydrochloric acid and the balance of water.

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

[0046] As a further technical solution of the present invention, the permeability range n includes 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] Through the above method, the relationship between C, P2 / P1, and n is obtained as follows: C = a(P2 / P1) 2 +bn+d; where a, b, and d are correlation coefficients.

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

[0051] Thus, the comprehensive evaluation parameter of the self-steering acidification steering effect M = a (P2 / P1) is obtained. 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 example uses cores and slabs from Block A for experimentation. The formula of the self-diverting acid is: 6% self-diverting agent, 3% corrosion inhibitor, 1% corrosion inhibitor enhancer, 2% iron ion stabilizer, 20% hydrochloric acid and the balance water.

[0055] A method for comprehensively evaluating the steering effect of self-steering acidification includes the following steps:

[0056] (1) A dual core flow device was used to conduct experiments on cores with different permeability extremes n (10, 20, 30, 40, 50). The initial permeability of the low permeability core was measured with standard brine as K1, and the pressure P1 at the K1 value was recorded. The high permeability core was then plugged with a self-steering acid system. The steering 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 measured with the same displacement of standard brine, and the permeability change rate C = (K3-K1) / K1 was calculated. The results are recorded in Table 1. Figure 1 It is the relationship curve between the permeability change rate, the permeability extreme difference and the dimensionless pressure in this embodiment.

[0057] Table 1. Experimental data of self-diverting acid diverting pressure and permeability changes

[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) According to the fitting regression curve of the permeability change rate C, the permeability range n, and the 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 the acid-etched fracture conductivity device, at different closing pressures P c The rock plate was tested under the following conditions, and the conductivity D1 was measured under the closing pressure of 10MPa, 20MPa, 30MPa, 40MPa, 50MPa, and 60MPa, respectively. The conductivity D2 of the acid-etched crack was measured under the same displacement and excessive self-diverting acid system. The rock plate 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=A1 / A2 of the acid-etched crack was calculated. The results are shown in Table 2. Figure 2 It is the relationship curve between the dimensionless flow conductivity and the dimensional closing pressure and roughness of this embodiment.

[0062] Table 2. Experimental data of self-steering 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 closing pressure P in Table 2 c The fitting regression curve of D2 / D1 and the dimensionless conductivity D2 / D1 and roughness S can be obtained. c ) The relationship is:

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

[0066] (5) Obtain comprehensive evaluation parameters of the diversion effect of self-diverting acidizing 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 example uses cores and slabs from Block B for experimentation. The formula of the self-diverting acid is: 8% self-diverting agent, 3% corrosion inhibitor, 1% corrosion inhibitor enhancer, 2% iron ion stabilizer, 20% hydrochloric acid and the balance water.

[0070] A method for comprehensively evaluating the steering effect of self-steering acidification includes the following steps:

[0071] (1) A dual core flow device was used to conduct experiments on cores with different permeability extremes n (10, 20, 30, 40, 50). The initial permeability of the low permeability core was measured with standard brine as K1, and the pressure P1 at the K1 value was recorded. The high permeability core was then plugged with a self-steering acid system. The steering 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 measured with the same displacement of standard brine, and the permeability change rate C = (K3-K1) / K1 was calculated. The results are recorded in Table 3. Figure 3 It is the relationship curve between the permeability change rate, the permeability extreme difference and the dimensionless pressure in this embodiment.

[0072] Table 3. Experimental data of self-diverting acid diverting pressure and permeability changes

[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) According to the fitting regression curve 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 the acid-etched fracture conductivity device, at different closing pressures P cThe rock plate was tested under the following conditions, and the conductivity D1 was measured under the closing pressure of 10MPa, 20MPa, 30MPa, 40MPa, 50MPa, and 60MPa, respectively. The conductivity D2 of the acid-etched crack was measured under the same displacement and excessive self-diverting acid system. The rock plate 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=A1 / A2 of the acid-etched crack was calculated. The results are shown in Table 4. Figure 4 It is the relationship curve between the dimensionless flow conductivity and the dimensional closing pressure and roughness of this embodiment.

[0077] Table 4. Experimental data of self-steering acid conductivity and roughness

[0078]

[0079]

[0080] (4) According to the dimensionless closing pressure P in Table 2 c The fitting regression curve of D2 / D1 and the dimensionless conductivity D2 / D1 and roughness S can be obtained. c ) The relationship is:

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

[0082] (5) Obtain comprehensive evaluation parameters of the diversion effect of self-diverting acidizing 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 implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method 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 in the scope of protection of the present invention.

Claims

1. A comprehensive evaluation method for the diversion effect of self-diverting acidification, characterized in that: The following steps are involved: (1) Using a dual core flow device, the initial permeabilities K1 and K2 of low-permeability and high-permeability cores were measured with standard brine, and the pressure P1 at the K1 value was recorded. The high-permeability core was then plugged with a self-steering acid system, and the steering 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 measured with the same displacement of standard brine, and the permeability change rate C = (K3-K1) / K1 was calculated; (2) Conducting experiments with cores with different permeability extreme differences n, repeating step (1), and determining the correlation coefficient between C and f(P2 / P1, n) based on the fitted regression curve of the permeability change rate C, the permeability extreme difference n, and the dimensionless pressure P2 / P1; (3) The conductivity of the acid-etched fractures is measured by using an acid-etched fracture conductivity device at a set closing pressure, D1. The conductivity of the acid-etched fractures measured under the same displacement and excess self-diverting acid system is D2. The rock plate before and after acid etching is scanned to obtain the surface area A1 before acid etching and the surface area A2 after acid etching. The roughness of the acid-etched fracture is calculated to be S=A1 / A2; (4) Using different closing pressures P c Experiments were conducted on the rock plate, and step (3) was repeated. Based on the dimensionless closing pressure P c / 10 and the dimensionless conductivity D2 / D1, roughness S fitting regression curve, determine D2 / D1 and f(S, P c / 10) correlation coefficient; (5) Obtain the comprehensive evaluation parameter of the self-steering acidification steering effect M = f(P2 / P1, n) + f(S, P c / 10).

2. A self-steering acidification and steering effect comprehensive evaluation method according to claim 1, characterized in that: 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 multiple difference between the high permeability core and the low permeability core is 1-50.

3. A self-steering acidification and steering effect comprehensive evaluation method according to claim 1, characterized in that: The self-diverting acid system comprises the following components: a self-diverting agent, a corrosion inhibitor, a corrosion inhibitor synergist, an iron ion stabilizer, hydrochloric acid and the balance of water.

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

5. The method for comprehensive evaluation of the self-steering acidification steering effect according to claim 1, characterized in that: The permeability range n includes 10, 20, 30, 40 and 50.

6. A self-steering acidification and steering effect comprehensive evaluation method 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. A method for comprehensive evaluation of 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 comprehensive evaluation of 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; Among them, a, b, and d are correlation coefficients.

9. A method for comprehensive evaluation of self-steering acidification steering effect according to claim 8, characterized in that: The D2 / D1 and S, P c / 10 is: D2 / D1=eS 2 +gln(P c / 10)+h; Among them, e, g, and h are correlation coefficients.

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

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