Acid fracturing transformation method and device for complex lithologic carbonate reservoir

Abstract

The invention relates to the technical field of carbonate rock transformation, and particularly discloses an acid fracturing transformation method and device for a complex lithologic carbonate rock reservoir, and the method comprises the steps: carrying out bridge plug segmentation on the complex lithologic carbonate rock reservoir; the fracturing fluid A, the acid fluid A, the acid fluid B, the fracturing fluid B and the fracturing fluid C are sequentially injected into the reservoir subjected to bridge plug segmentation, and / or the fracturing fluid A, the acid fluid A, the acid fluid B and the fracturing fluid B are sequentially injected into the reservoir subjected to bridge plug segmentation, and an artificial fracture is formed and used for improving the physical property and the seepage capacity of a reservoir matrix and reducing potential damage to the reservoir caused by excessive corrosion of the acid fluid. The method gives consideration to the modification effects of hydraulic fractures and acid etching fractures, fractures are formed through fracturing fluid to communicate with a matrix, and through double-slug high-displacement injection of acid liquor with a certain concentration, the physical property and seepage capacity of the reservoir matrix are improved, the flow conductivity of reservoir fractures is not affected, the effectiveness of artificial fractures is improved, and damage to the reservoir caused by excessive corrosion of the acid liquor is reduced; and the volume of reservoir transformation and the flow conductivity of fractures with different scales can be improved.

Description

Technical Field

[0001] This invention relates to the field of carbonate rock modification technology, specifically to an acid fracturing modification method and apparatus for complex carbonate rock reservoirs. Background Technology

[0002] Currently, conventional carbonate rock acid fracturing techniques both domestically and internationally include conventional acid fracturing, pre-fracturing, closed-loop acid fracturing, balanced acid fracturing, and multi-stage injection acid fracturing. In recent years, based on the continuous deepening of reservoir characteristics, clean self-directing acid fracturing, composite acid fracturing, ultra-large repeated acid fracturing, hydraulic jet segmented acid fracturing, and network fracture acid fracturing have been developed, which better meet the acid fracturing stimulation technology requirements of different types of carbonate rock reservoirs.

[0003] For acid fracturing working fluid systems, i.e., acid solutions, there are generally types including ordinary hydrochloric acid, gelling acid, crosslinking acid, emulsified acid, viscoelastic surfactant self-adaptive acid, and self-generating acid, mainly to meet the purposes of slowing down the acid-rock reaction rate, extending the acid solution's action distance, and reducing filtration loss. The basic acid solution used is mainly 15-28% industrial hydrochloric acid.

[0004] Although various acid systems have been developed to meet the characteristics of different reservoirs, the exploration and development of carbonate rocks continues to pose challenges to conventional acid fracturing techniques for high-temperature, deep, and complex lithological carbonate reservoirs, necessitating the development of new acid systems to meet these needs. The Permian Mao-1st Formation limestone-type carbonate reservoir in the Sichuan Basin has complex lithology and high reservoir temperature. During acid injection, the complex lithology makes it easy for quartz fragments and clay minerals to deposit after acid etching, reducing the conductivity of fractures formed by acid etching and affecting the increase and stability of oil and gas production.

[0005] Based on this technical background, this invention studies an acid fracturing method and apparatus for complex lithological carbonate reservoirs. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides an acid fracturing stimulation method and apparatus for complex carbonate reservoirs. This method balances the effects of hydraulic fractures and acid-etched fractures. It creates fractures by using fracturing fluid to connect with the matrix, and then injects a high-volume, dual-segment plug of a certain concentration of acid to improve the physical properties and permeability of the reservoir matrix without affecting the conductivity of the reservoir fractures. This enhances the effectiveness of artificial fractures and reduces the potential damage to the reservoir from excessive acid dissolution. It is beneficial for increasing the volume of reservoir stimulation and the conductivity of fractures of different sizes, expanding the scope and effect of reservoir acid fracturing stimulation, and improving the production and stabilization of oil and gas wells.

[0007] To achieve the above objectives, a first aspect of the present invention provides an acid fracturing method for complex lithological carbonate reservoirs, comprising:

[0008] Bridge plug segmentation for complex lithological carbonate reservoirs;

[0009] After the reservoir is segmented by bridge plugs, fracturing fluid A, acid A, acid B, fracturing fluid B, and fracturing fluid C are injected sequentially, and / or fracturing fluid A, acid A, acid B, and fracturing fluid B are injected sequentially to form artificial fractures. This is used to improve the reservoir matrix properties and permeability, and to reduce the potential damage to the reservoir caused by excessive acid dissolution.

[0010] A second aspect of the present invention provides an acid fracturing device for complex lithological carbonate reservoirs, comprising:

[0011] Bridge plug segmentation module, used for bridge plug segmentation of complex lithological carbonate reservoirs;

[0012] The injection module is used to sequentially inject fracturing fluid A, acid A, acid B, fracturing fluid B, and fracturing fluid C into the reservoir after bridge plug segmentation, and / or sequentially inject fracturing fluid A, acid A, acid B, and fracturing fluid B to form artificial fractures, which are used to improve the reservoir matrix properties and permeability, and reduce the potential damage to the reservoir caused by excessive acid dissolution.

[0013] The beneficial effects of this invention include:

[0014] The acid fracturing stimulation method for complex carbonate reservoirs proposed in this invention takes into account the stimulation effects of hydraulic fractures and acid-etched fractures. It creates fractures by fracturing fluid to connect with the matrix, and injects a certain concentration of acid through a two-stage plug at high flow rate to improve the physical properties and permeability of the reservoir matrix, while not affecting the conductivity of the reservoir fractures. This improves the effectiveness of artificial fractures and reduces the potential damage to the reservoir caused by excessive acid dissolution. It is beneficial to increase the volume of reservoir stimulation and the conductivity of fractures of different sizes, increase the range and effect of reservoir acid fracturing stimulation, and improve the production and stabilization effect of oil and gas wells.

[0015] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0016] The above and other objects, features and advantages of the present invention will become more apparent from the more detailed description of exemplary embodiments of the invention in conjunction with the accompanying drawings.

[0017] Figure 1 This is a schematic flowchart of the acid fracturing stimulation method for complex lithological carbonate reservoirs proposed in this invention.

[0018] Figure 2 This is a schematic diagram comparing simulated fracture heights at different discharge rates in a specific embodiment of the acid fracturing stimulation method for complex lithological carbonate reservoirs proposed in this invention.

[0019] Figure 3This is a schematic diagram comparing the differences in stimulation volume under different cluster spacings in a specific embodiment of the acid fracturing stimulation method for complex lithological carbonate reservoirs proposed in this invention. Detailed Implementation

[0020] Preferred embodiments of the invention will now be described in more detail. While preferred embodiments of the invention are described below, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein.

[0021] This invention provides an acid fracturing stimulation method for complex lithological carbonate reservoirs, such as... Figure 1 As shown, it includes:

[0022] Bridge plug segmentation for complex lithological carbonate reservoirs;

[0023] After the bridge plug is segmented, fracturing fluid A, acid A, acid B, fracturing fluid B, and fracturing fluid C are injected sequentially into the reservoir to form artificial fractures. This is used to improve the reservoir matrix properties and permeability, and to reduce the potential damage to the reservoir caused by excessive acid dissolution.

[0024] This invention balances the effects of hydraulic fracturing and acid fracturing. It creates fractures by using fracturing fluid to connect with the matrix, and then injects a high-volume, two-stage acid solution of a certain concentration. This improves the matrix properties and permeability without affecting the reservoir's fracture conductivity, thereby enhancing the effectiveness of artificial fractures and reducing the potential damage to the reservoir from excessive acid dissolution. This approach is beneficial for increasing the volume of reservoir stimulation and the conductivity of fractures at different scales, expanding the range and effectiveness of acid fracturing stimulation, and ultimately improving the production and stabilization of oil and gas wells.

[0025] According to the present invention, the number of perforation clusters in a single segment of the bridge plug is 6-8, the spacing between each cluster is 10-50m, and the size of a single segment is 1600-1800m. 3 .

[0026] According to the present invention, the length of the artificial crack is 140-160m and the height is 44-48m.

[0027] According to the present invention, the viscosity of fracturing fluid A is greater than 25 mPa·s, and the injection rate is 20-22 m³ / s. 3 / min, injection volume is 250-300m³ 3 ;

[0028] The viscosity of fracturing fluid B is 8-15 mPa·s, and the injection rate is 16-18 m³ / s. 3 / min, injection volume is 150-200m³ 3 ;

[0029] The viscosity of fracturing fluid C is 10-20 mPa·s, and the injection rate is 8-10 m³ / s. 3 / min, injection volume 100-150m³ 3 .

[0030] Preferably, the viscosity of acid A is 1.5-3.0 mPa·s, and the injection rate is 16-18 m³ / s. 3 / min, injection volume is 150-200m³ 3 ;

[0031] The viscosity of acid B is 0.1-1.0 mPa·s, and the injection rate is 16-18 m³ / s. 3 / min, injection volume 90-150m³ 3 .

[0032] According to the present invention, fracturing fluid A is a guar gum fracturing fluid, and its composition formula by mass percentage is: 0.3-0.5% hydroxypropyl guar gum + 0.05-0.2% sodium carbonate + 0.2-0.4% crosslinking agent + 0.05-0.2% flow aid + 0.02-0.04% breaker, with the remainder being water;

[0033] Fracturing fluid B is slickwater, and its composition by mass percentage is: 0.10-0.20% drag reducer + 0.05-2.0% flow aid + 9-11% proppant, with the remainder being water;

[0034] Fracturing fluid C is slickwater, and its composition by mass percentage is: 0.1-0.3% drag reducer + 0.05-2.0% flow aid + 9-11% water.

[0035] According to the present invention, acid solution A is a drag-reducing acid, and its composition by mass percentage is: 4-5% hydrochloric acid + 0.05-0.07% thickener + 1.0-3.0% acid pressure corrosion inhibitor + 0.05-2.0% iron ion stabilizer.

[0036] +0.05-2.0% drainage aid, the remainder is water;

[0037] Acid B is a complex organic acid, and its composition by mass percentage is as follows: 3-5% formic acid + 1-3% acetic acid + 0.5-2% chelating acid + 1.0-3.0% acid pressure corrosion inhibitor + 0.05-2.0% iron ion stabilizer + 0.05-2.0% drainage aid, with the remainder being water.

[0038] Preferably, the proppant is 40 / 70 mesh ceramsite;

[0039] The diameter of the temporary plugging balls is 22-25 mm, or the particle size is 20-40 mesh.

[0040] The present invention will be described in more detail below through embodiments.

[0041] Example 1:

[0042] This embodiment proposes an acid fracturing stimulation method for complex carbonate reservoirs, and the specific implementation steps are as follows:

[0043] The system employs segmented bridge plugs, with 6-8 perforation clusters per segment, spacing between clusters of 10-50m, and a segment size of 1600-1800m. 3 ;

[0044] (1) Fracturing fluid A with a viscosity of 30 mPa·s and a flow rate of 20 m³ / s is injected into the reservoir through the oil and gas well casing. 3 / min, liquid volume 300m 3 ;

[0045] (2) Inject acid solution A, the viscosity of acid solution A is 2.0 mPa·s, and the injection rate is 18 m³ / s. 3 / min, injection volume is 200m³ 3 ;

[0046] (3) Inject acid solution B, the viscosity of acid solution B is 1.0 mPa·s, and the injection rate is 18 m³ / s. 3 / min, injection volume 150m 3 ;

[0047] (4) Inject fracturing fluid B with a viscosity of 15 mPa·s and an injection rate of 18 m³ / s. 3 / min, injection volume is 200m³ 3 ;

[0048] (5) Inject fracturing fluid C, viscosity 20 mPa·s, injection rate 10 m³ / s. 3 / min, injection volume is 100m³ 3 ;

[0049] (6) Inject fracturing fluid A with a viscosity greater than 30 mPa·s and an injection rate of 20 m³ / s. 3 / min, injection volume is 300m³ 3 ;

[0050] (7) Inject acid solution A, the viscosity of acid solution A is 2.0 mPa·s, and the injection rate is 18 m³ / s. 3 / min, injection volume is 200m³ 3 ;

[0051] (8) Inject acid solution B, the viscosity of acid solution B is 1.0 mPa·s, and the injection rate is 18 m³ / s. 3 / min, injection volume 150m 3 ;

[0052] (9) Inject fracturing fluid B, with a viscosity of 15 mPa·s and an injection rate of 18 m³ / s. 3 / min, injection volume is 200m³ 3 ;

[0053] Total liquid volume 1800m 3 The crack height is calculated to be 44m, and the half-length of the crack is 140-150m.

[0054] In this embodiment, fracturing fluid A is guar gum fracturing fluid, and its composition by mass percentage is: 0.4% HPG (hydroxypropyl guar gum) + 0.1% sodium carbonate + 0.3% crosslinking agent + 0.1% flow aid + 0.03% breaker, with the remainder being water;

[0055] Acid A is a drag-reducing acid, and its composition by mass percentage is: 4-5% hydrochloric acid + 0.06% thickener + 2.0% acid pressure corrosion inhibitor + 1.0% iron ion stabilizer + 0.1% drainage aid, with the remainder being water;

[0056] Acid B is a complex organic acid, and its composition by mass percentage is: 4% formic acid + 2% acetic acid + 1% chelating acid + 2.0% acid pressure corrosion inhibitor + 1.0% iron ion stabilizer + 0.1% drainage aid, with the remainder being water;

[0057] Fracturing fluid B is slickwater, and its composition by mass percentage is: 0.15% drag reducer + 0.1% flow aid, and also contains 10% proppant, which is 40 / 70 mesh ceramsite, with the remainder being water;

[0058] Fracturing fluid C is slickwater, and its composition by mass percentage is: 0.2% drag reducer + 0.1% flow aid, and also contains 100kg of temporary plugging balls with a diameter of 22-25mm and a particle size of 20-40 mesh, with the remainder being water.

[0059] This embodiment simulates the differences in modified volume under different displacements, simulated suture heights, and different cluster spacings, as shown below. Figure 2 , Figure 3 As shown.

[0060] Example 2:

[0061] This embodiment provides an acid fracturing stimulation method for complex lithological carbonate reservoirs, such as... Figure 1 As shown, it includes:

[0062] Bridge plug segmentation for complex lithological carbonate reservoirs;

[0063] After the bridge plug is segmented, fracturing fluid A, acid A, acid B, fracturing fluid B, fracturing fluid C, fracturing fluid A, acid A, acid B, and fracturing fluid B are injected sequentially into the reservoir to form artificial fractures. This is used to improve the reservoir matrix properties and permeability, and to reduce the potential damage to the reservoir caused by excessive acid dissolution.

[0064] In this embodiment, the number of perforation clusters in a single segment of the bridge plug is 6-8, the spacing between each cluster is 10-50m, and the size of a single segment is 1600-1800m. 3 ;

[0065] The artificial cracks are 140-160m long and 44-48m high;

[0066] In this embodiment, the viscosity of fracturing fluid A is 35 mPa·s, and the injection rate is 22 m³ / s. 3 / min, injection volume is 300m³ 3 ;

[0067] The viscosity of fracturing fluid B is 15 mPa·s, and the injection rate is 18 m³ / s. 3 / min, injection volume is 200m³ 3 ;

[0068] The fracturing fluid C has a viscosity of 20 mPa·s and an injection rate of 10 m³ / s. 3 / min, injection volume 150m 3 ;

[0069] Acid A has a viscosity of 3.0 mPa·s and an injection rate of 18 m³ / s. 3 / min, injection volume is 200m³ 3 ;

[0070] The viscosity of acid B is 1.0 mPa·s, and the injection rate is 18 m³ / s. 3 / min, injection volume 150m 3 ;

[0071] According to the present invention, fracturing fluid A is a guar gum fracturing fluid, and its composition formula by mass percentage is: 0.5% hydroxypropyl guar gum + 0.2% sodium carbonate + 0.4% crosslinking agent + 0.2% flow aid + 0.04% breaker, with the remainder being water;

[0072] Fracturing fluid B is slickwater, and its composition by mass percentage is: 0.20% drag reducer + 2.0% flow aid + 11% proppant, with the remainder being water;

[0073] Fracturing fluid C is slickwater, and its composition by mass percentage is: 0.3% drag reducer + 2.0% flow aid + 11%, with the remainder being water;

[0074] Acid A is a drag-reducing acid, and its composition by mass percentage is: 5% hydrochloric acid + 0.07% thickener + 3.0% acid pressure corrosion inhibitor + 2.0% iron ion stabilizer + 2.0% drainage aid, with the remainder being water;

[0075] Acid B is a complex organic acid, and its composition by mass percentage is: 5% formic acid + 3% acetic acid + 2% chelating acid + 3.0% acid pressure corrosion inhibitor + 2.0% iron ion stabilizer + 2.0% drainage aid, with the remainder being water;

[0076] In this embodiment, the proppant is 40 / 70 mesh ceramsite;

[0077] The diameter of the temporary plugging ball is 22-25mm.

[0078] Example 3:

[0079] This embodiment provides an acid fracturing device for complex lithological carbonate reservoirs, including:

[0080] Bridge plug segmentation module, used for bridge plug segmentation of complex lithological carbonate reservoirs;

[0081] The injection module is used to sequentially inject fracturing fluid A, acid A, acid B, fracturing fluid B, fracturing fluid C, fracturing fluid A, acid A, acid B, and fracturing fluid B into the reservoir after bridge plug segmentation to form artificial fractures. This is used to improve the reservoir matrix properties and permeability, and reduce the potential damage to the reservoir caused by excessive acid dissolution.

[0082] In this embodiment, the number of perforation clusters in a single segment of the bridge plug is 6-8, the spacing between each cluster is 10-50m, and the size of a single segment is 1600-1800m. 3 ;

[0083] The artificial cracks are 140-160m long and 44-48m high;

[0084] In this embodiment, the viscosity of fracturing fluid A is 35 mPa·s, and the injection rate is 22 m³ / s. 3 / min, injection volume is 300m³ 3 ;

[0085] The viscosity of fracturing fluid B is 15 mPa·s, and the injection rate is 18 m³ / s. 3 / min, injection volume is 200m³ 3 ;

[0086] The fracturing fluid C has a viscosity of 20 mPa·s and an injection rate of 10 m³ / s. 3 / min, injection volume 150m 3 ;

[0087] Acid A has a viscosity of 3.0 mPa·s and an injection rate of 18 m³ / s.3 / min, injection volume is 200m³ 3 ;

[0088] The viscosity of acid B is 1.0 mPa·s, and the injection rate is 18 m³ / s. 3 / min, injection volume 150m 3 ;

[0089] According to the present invention, fracturing fluid A is a guar gum fracturing fluid, and its composition formula by mass percentage is: 0.5% hydroxypropyl guar gum + 0.2% sodium carbonate + 0.4% crosslinking agent + 0.2% flow aid + 0.04% breaker, with the remainder being water;

[0090] Fracturing fluid B is slickwater, and its composition by mass percentage is: 0.20% drag reducer + 2.0% flow aid + 11% proppant, with the remainder being water;

[0091] Fracturing fluid C is slickwater, and its composition by mass percentage is: 0.3% drag reducer + 2.0% flow aid + 11%, with the remainder being water;

[0092] Acid A is a drag-reducing acid, and its composition by mass percentage is: 5% hydrochloric acid + 0.07% thickener + 3.0% acid pressure corrosion inhibitor + 2.0% iron ion stabilizer + 2.0% drainage aid, with the remainder being water;

[0093] Acid B is a complex organic acid, and its composition by mass percentage is: 5% formic acid + 3% acetic acid + 2% chelating acid + 3.0% acid pressure corrosion inhibitor + 2.0% iron ion stabilizer + 2.0% drainage aid, with the remainder being water;

[0094] In this embodiment, the proppant is 40 / 70 mesh ceramsite;

[0095] The diameter of the temporary plugging ball is 22-25mm.

[0096] The acid fracturing stimulation method for complex carbonate reservoirs proposed in the embodiments of the present invention takes into account the stimulation effects of hydraulic fractures and acid-etched fractures. It creates fractures by fracturing fluid to connect with the matrix, and injects a certain concentration of acid through a two-stage plug at high flow rate to improve the physical properties and permeability of the reservoir matrix, while not affecting the conductivity of the reservoir fractures. This improves the effectiveness of artificial fractures and reduces the potential damage to the reservoir caused by excessive acid dissolution. It is beneficial to increase the volume of reservoir stimulation and the conductivity of fractures of different sizes, increase the range and effect of reservoir acid fracturing stimulation, and improve the production and stabilization effect of oil and gas wells.

[0097] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A method for acid fracturing stimulation of complex carbonate rock reservoirs, characterized in that, include: Bridge plug segmentation for complex lithological carbonate reservoirs; After the reservoir is segmented by bridge plugs, fracturing fluid A, acid A, acid B, fracturing fluid B, and fracturing fluid C are injected sequentially, and / or fracturing fluid A, acid A, acid B, and fracturing fluid B are injected sequentially to form artificial fractures. This is used to improve the reservoir matrix properties and permeability, and to reduce the potential damage to the reservoir caused by excessive acid dissolution.

2. The method according to claim 1, characterized in that, The bridge plug segment has 6-8 perforation clusters per segment, with a spacing of 10-50m between each cluster, and a segment size of 1600-1800m. 3 .

3. The method according to claim 1, characterized in that, The artificial cracks are 140-160m long and 44-48m high.

4. The method according to claim 1, characterized in that, The viscosity of the fracturing fluid A is greater than 25 mPa·s, and the injection rate is 20-22 m³ / s. 3 / min, injection volume is 250-300m³ 3 ; The fracturing fluid B has a viscosity of 8-15 mPa·s and an injection rate of 16-18 m³ / s. 3 / min, injection volume is 150-200m³ 3 ; The fracturing fluid C has a viscosity of 10-20 mPa·s and an injection rate of 8-10 m³ / s. 3 / min, injection volume 100-150m³ 3 .

5. The method according to claim 1, characterized in that, The viscosity of acid solution A is 1.5-3.0 mPa·s, and the injection rate is 16-18 m³ / s. 3 / min, injection volume is 150-200m³ 3 ; The viscosity of acid solution B is 0.1-1.0 mPa·s, and the injection rate is 16-18 m³ / s. 3 / min, injection volume 90-150m³ 3 .

6. The method according to claim 1, characterized in that, The fracturing fluid A is a guar gum fracturing fluid, and its composition by mass percentage is: 0.3-0.5% hydroxypropyl guar gum + 0.05-0.2% sodium carbonate + 0.2-0.4% crosslinking agent + 0.05-0.2% flow aid + 0.02-0.04% breaker, with the remainder being water; The fracturing fluid B is slickwater, and its composition by mass percentage is: 0.10-0.20% drag reducer + 0.05-2.0% flow aid + 9-11% proppant, with the remainder being water; The fracturing fluid C is slickwater, and its composition by mass percentage is: 0.1-0.3% drag reducer + 0.05-2.0% flow aid + 9-11% water.

7. The method according to claim 1, characterized in that, The acid solution A is a drag-reducing acid, and its composition by mass percentage is: 4-5% hydrochloric acid + 0.05-0.07% thickener + 1.0-3.0% acid pressure corrosion inhibitor + 0.05-2.0% iron ion stabilizer + 0.05-2.0% drainage aid, with the remainder being water.

8. The method according to claim 1, characterized in that, The acid solution B is a complex organic acid, and its composition by mass percentage is: 3-5% formic acid + 1-3% acetic acid + 0.5-2% chelating acid + 1.0-3.0% acid pressure corrosion inhibitor + 0.05-2.0% iron ion stabilizer + 0.05-2.0% drainage aid, with the remainder being water.

9. The method according to claim 6, characterized in that, The proppant is 40 / 70 mesh ceramsite; The temporary plugging ball has a diameter of 22-25 mm, or a particle size of 20-40 mesh.

10. An acid fracturing device for complex carbonate rock reservoirs, characterized in that, include: Bridge plug segmentation module, used for bridge plug segmentation of complex lithological carbonate reservoirs; The injection module is used to sequentially inject fracturing fluid A, acid A, acid B, fracturing fluid B, and fracturing fluid C into the reservoir after bridge plug segmentation, and / or sequentially inject fracturing fluid A, acid A, acid B, and fracturing fluid B to form artificial fractures, which are used to improve the reservoir matrix properties and permeability, and reduce the potential damage to the reservoir caused by excessive acid dissolution.

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