Retarded acid system for acidification transformation of clay type shale oil reservoir and application of retarded acid system

Abstract

The invention belongs to the field of oil and gas field development, and discloses a retarded acid system for acidification transformation of clay type shale oil reservoirs and application of the retarded acid system. According to the method, an acid rock reaction speed equation is taken as a theoretical basis, the control on the acid rock speed is realized by controlling two main parameters, namely H + concentration and an acid rock contact area, which influence the reaction speed, so that the deep penetrating power of the acid liquor is realized, the acid liquor can effectively enter the deep part of a reservoir, and meanwhile, the generation of acidification secondary precipitation can be reduced; the surfactant additive is added to reduce the influence of a water-based acid liquid system on high-clay minerals, blockage removal and acidification transformation are mainly performed on calcite, dolomite, siderite and pyrite in high-clay reservoir stratification, an effective acid etching channel is formed, shale oil rock wettability is changed by adding the surfactant additive, the fluidity of crude oil is improved, and the high-clay reservoir stratification effect is improved. While an effective oil transportation channel is formed through effective transformation, the fluidity of crude oil is improved, the resistance of rocks is reduced, and the purpose of high yield is achieved.

Description

Technical Field

[0001] The invention belongs to the field of oil and gas field development, and relates to a slow-rate acid system for acidification transformation of clay-type shale oil reservoirs and application thereof. Background Art

[0002] As the proportion of unconventional reservoirs in exploration and development increases, the exploration and development of shale reservoirs in Jilin Oilfield has become the main replacement resource for the next step. In the clay shale oil reservoirs currently developed in the oil field, the shale is characterized by developed bedding, poor matrix properties, and a clay mineral content of 50-60%. The wetting angle between shale oil rock and oil phase is 4-20°, and the wetting angle with water phase is 40-90°. The reservoir is generally highly oil-wet and weakly hydrophilic. Conventional fracturing transformation methods have problems such as embedded fracturing proppant, low conductivity, long oil-seeping period after fracturing, and severe sand production, and the overall effect is poor. Therefore, how to combine the characteristics of clay shale rocks and reservoirs, effectively transform the reservoir, form a seepage channel with high conductivity, and reduce the expansion and migration of clay, is the key to the effective transformation of clay shale reservoirs. Through research, it is found that acidification transformation technology is a better development technology for shale oil reservoirs. In order to effectively target the high clay mineral content of clay-type shale oil reservoirs while ensuring a large acidizing transformation volume, an acid system with high retarding capacity is needed, as well as an acid system with a certain protective ability for high clay mineral reservoirs.

[0003] The most commonly used retarder systems are mainly polyhydric acid and fluoroboric acid. The main mechanism of action is to reduce the H + , reducing the reaction rate and having a certain retarding ability, this type of acid still has certain limitations for clay shale with high mudstone content. Summary of the invention

[0004] In order to overcome the shortcomings of the prior art and solve the above-mentioned problems, the present invention provides a slow acid system for acidizing and reforming clay-type shale reservoirs and its application. The present invention takes the acid-rock reaction rate equation as the theoretical basis. At a certain reaction temperature, the acid-rock reaction rate is mainly related to the acid-rock contact surface and the H + The concentration is related to the reaction rate by controlling the two main parameters H + The concentration and acid-rock contact area can be used to control the acid-rock velocity, thereby achieving the deep penetration ability of the acid, which can effectively enter the deep reservoir. At the same time, it can reduce the generation of secondary precipitation due to acidification, reduce the impact of the water-based acid system on high-clay minerals, and achieve unblocking and acidification transformation of calcite, dolomite, siderite, and pyrite in the stratum of high-clay reservoirs, forming an effective acid etching channel. The wettability of shale oil rocks is changed by adding surfactant additives to improve the fluidity of crude oil. While achieving effective transformation to form an effective oil transportation channel, the fluidity of crude oil is improved and the resistance of rocks is reduced to achieve the purpose of high production.

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

[0006] A slow-rate acid system for acidizing and reforming clay-type shale reservoirs, specifically: a slow-rate acid system for acidizing and reforming clay-type shale reservoirs, which simultaneously changes the contact area and effective hydrogen ion concentration, two important parameters that affect the acid-rock reaction rate, to achieve the technical requirements of high slow-rate. Organic polycarboxylates are used to form polycarboxylic acids in the way of strong acid to weak acid, and the multi-stage ionization of polycarboxylic acids is used to reduce H + concentration, and at the same time, organic polycarboxylic acids and carboxylates are adsorbed to reservoir rocks to form an adsorption film, thereby reducing the contact area between the acid and clay minerals and reducing the acid-rock reaction rate; organic polycarboxylates can complex the metal ions in the solution to prevent them from forming metal fluorides that cause precipitation, thereby avoiding secondary damage to the reservoir; the oil washing system changes the generally strong oil-wet and weak water-wet characteristics of the original shale oil rock, and improves the fluidity of the crude oil.

[0007] The present invention also provides a slow acid solution for the slow acid system, which comprises the following components in percentage by mass:

[0008]

[0009] Furthermore, the main acid solution in the slow acid solution is a medium-strong acid system such as hydrochloric acid system and phosphoric acid.

[0010] Furthermore, the organic polycarboxylate in the slow acid solution is any one or two of disodium hydroxyethylene diphosphate and heptasodium diethylenetriamine penta methylene phosphonate.

[0011] Furthermore, the high temperature corrosion inhibitor in the slow acid solution is a quaternary ammonium salt corrosion inhibitor system synthesized from benzyl chloride and 3-methylpyridine or other commercially available corrosion inhibitor systems with high compatibility.

[0012] Furthermore, the iron ion stabilizer in the slow acid solution is an iron ion stabilizer of an EDTAD system including an iron chelating agent.

[0013] Furthermore, the clay stabilizer in the slow acid solution is a clay stabilizer comprising potassium chloride and a poly-small cation system.

[0014] Furthermore, the oil washing surfactant system in the slow acid solution is a nano non-ionic surfactant system.

[0015] The present invention also provides a method for preparing the above slow acid solution, which specifically comprises the following steps:

[0016] Weigh the main acid solution, organic polycarboxylate, high temperature corrosion inhibitor, iron ion stabilizer, clay stabilizer, washing oil surfactant system and water according to the mass percentage ratio, mix them at room temperature, shake well and let them stand for use.

[0017] Furthermore, the main acid solution is preferably hydrochloric acid.

[0018] The present invention also claims to protect the use of the above slow acid system for acidizing and reforming clay-type shale oil reservoirs in acidizing and reforming clay-type shale oil reservoirs.

[0019] The present invention also claims to protect the application of the above slow acid system for acidizing and reforming clay shale oil reservoirs in Da'an and Tahucheng clay shale oil in Jilin Oilfield.

[0020] The specific application operations are:

[0021] The beneficial effects of the present invention compared with the prior art are:

[0022] The slow-rate acid system provided by the present invention can prolong the acidification time. The slow-rate acid system has the following performances: by limiting the ratio of the main acid to the organic polycarboxylate, the shale core dissolution rate is between 8% and 30%, and the slow-rate effect of 30% to 80% can be achieved. The static corrosion rate at 90°C is less than 3g / m 2 .h, contact angle 5.33°, strong hydrophilicity; anti-swelling rate reaches more than 64%.

[0023] It can achieve deep acidification transformation of shale bedding, has a certain protective function on clay minerals with little impact, and has the characteristics of changing rock wettability and increasing crude oil fluidity, and is particularly suitable for deep acidification transformation of high-clay shale reservoirs. The slow acid system provided by the present invention has been field tested in 9 wells in clay-type shale oil areas such as Qian'an, Da'an, and Tahucheng in Jilin Oilfield, and has achieved good application results, showing obvious effects of increasing liquid and oil, and has high practicality. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The present invention is further described below in conjunction with the accompanying drawings

[0025] Figure 1 It is a retarding mechanism diagram of the retarding acid system provided by the present invention;

[0026] Figure 2 This is a diagram showing the mechanism of changing wettability of the detergent surfactant system provided by the present invention;

[0027] Figure 3 The content and distribution diagram of rock components in the acidification transformation of shale reservoirs provided by the present invention;

[0028] Figure 4 It is a wettability characterization diagram of shale reservoir provided by the present invention;

[0029] Figure 5 It is a time diagram of acid-rock reaction of different embodiments provided by the present invention;

[0030] Figure 6 It is a diagram of acidizing etching of shale core by the slow acid system provided by the present invention; wherein Figure (a) is a comparison diagram of the plane acidizing reaction of the shale core of Well Cha 35 before and after; Figure (b) is a comparison diagram of the bedding surface acidizing reaction of the shale core of Well Cha 35 before and after. DETAILED DESCRIPTION

[0031] The present invention is described in detail below by specific examples, but the protection scope of the present invention is not limited. Unless otherwise specified, the experimental methods used in the present invention are all conventional methods, and the experimental equipment, materials, reagents, etc. used can be obtained from commercial channels.

[0032] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0033] In order to make the objectives, technical solutions and advantages of the present invention more clear, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0034] Example 1

[0035] The system is calculated according to the mass percentage of 8% hydrochloric acid + 1% disodium hydroxyethylene diphosphate + 1% heptasodium diethylenetriamine pentamethylene phosphonate + 1.5% high temperature corrosion inhibitor + 0.5% iron ion stabilizer + 0.5% clay stabilizer + 0.5% washing oil surfactant. The components are mixed at room temperature, shaken and allowed to stand to obtain a slow acid acidifying solution.

[0036] Example 2

[0037] Calculate the system of 10% hydrochloric acid + 1% disodium hydroxyethylene diphosphate + 1% heptasodium diethylenetriamine pentamethylenephosphonate + 1.5% high temperature corrosion inhibitor + 0.5% iron ion stabilizer + 0.5% clay stabilizer + 0.5% detergent surfactant according to the mass percentage, mix the components at room temperature, shake well and let stand to prepare slow acid acidifying solution; Figure 5 In Example 2, the reaction time required is 6 hours when pure hydrochloric acid (4 hours) is used to achieve the same dissolution rate, which effectively slows down the acid-rock reaction rate.

[0038] Example 3

[0039] Calculate the system of 10% hydrochloric acid + 2% disodium hydroxyethylene diphosphate + 1% heptasodium diethylenetriamine pentamethylenephosphonate + 1.5% high temperature corrosion inhibitor + 0.5% iron ion stabilizer + 0.5% clay stabilizer + 0.5% detergent surfactant according to the mass percentage, mix the components at room temperature, shake well and let stand to prepare slow acid acidifying solution; Figure 5In Example 3, the reaction time required is 8 hours when pure hydrochloric acid (4 hours) reaches the same dissolution rate, which effectively slows down the acid-rock reaction rate. Figure 6 (a) It can be seen that after the acidification reaction, obvious grooves appeared on the shale core plane of Well Cha 35, achieving non-uniform etching; Figure 6 (b) It can be seen that obvious acid-etched holes also appear on the core bedding surface.

[0040] Example 4

[0041] Calculate the system of 10% hydrochloric acid + 3% disodium hydroxyethylene diphosphate + 2% heptasodium diethylenetriamine pentamethylenephosphonate + 1.5% high temperature corrosion inhibitor + 0.5% iron ion stabilizer + 0.5% clay stabilizer + 0.5% detergent surfactant according to the mass percentage, mix the components at room temperature, shake well and let stand to prepare slow acid acidifying solution; Figure 5 In Example 4, the reaction time required is 10 hours when pure hydrochloric acid (4 hours) is used to achieve the same dissolution rate. The addition of organic polycarboxylates at different contents reflects different abilities to slow down the acid-rock reaction rate. The larger the amount, the stronger the deceleration ability.

[0042] Example 5

[0043] The system is calculated according to the mass percentage of 15% hydrochloric acid + 3% disodium hydroxyethylene diphosphate + 2% heptasodium diethylenetriamine pentamethylene phosphonate + 1.5% high temperature corrosion inhibitor + 0.5% iron ion stabilizer + 0.5% clay stabilizer + 0.5% washing oil surfactant. The components are mixed at room temperature, shaken and allowed to stand to obtain a slow acid acidifying solution.

[0044] Application Example 1

[0045] The slow-rate acidizing fluid prepared in Example 3 was applied to the field investigation well 35 in the Da'an clay-type shale oil area of ​​Jilin Oilfield.

[0046] The specific implementation operation is: Acidizing is used to transform the reservoir in Bu 8, Bu 7, Bu 6, Bu 4 and Bu 3 layers of the Qing 1st section of Well Cha 35 to dissolve the calcite, dolomite and iron ore components in the reservoir layer structure and improve the deep seepage capacity of the reservoir. According to the preparation method of Example 3, the acid system is prepared for 300m 3 The system was used to examine the target layer of Well 35, and the core dissolution rate was 18% and the corrosion rate was 1.2 g / m 2 .h, slow rate 62%, the construction process uses 1-1.5m3 / min displacement to inject acid, and then inject 1-1.5m 3 / min displacement injection 30m 3 The well was replaced with clean water, and the well was shut down for 24 hours before being reopened for production. The application result showed that the test oil production was 5m 3 Liquid, 3.5t oil.

[0047] Application Example 2

[0048] In the field well Hei 120-7 in the clay shale oil area of ​​Qian'an area of ​​Jilin Oilfield, 150m of acid solution system was prepared before applying the slow acid acidizing solution prepared in Example 2 of the present invention. 3 The core dissolution rate of this system for the target layer of Heilongjiang Well 120-7 was 27% and the corrosion rate was 1.54g / m 2 .h, slow rate 52%, construction process using 1-2m 3 / min displacement to inject acid, then inject 1-2m 3 / min displacement injection 25m 3 The well was replaced with clean water, and the well was shut down for 24 hours before being reopened for production. The application result showed that the test oil production was 15m 3 Liquid, 8t oil.

[0049] The above-described embodiments are only preferred embodiments of the present invention, and are not all feasible embodiments of the present invention. For those skilled in the art, any obvious changes made to it without departing from the principles and spirit of the present invention should be considered to be included in the scope of protection of the claims of the present invention. Although the present invention has been described above with reference to the embodiments, various improvements can be made to it and the components thereof can be replaced by equivalents without departing from the scope of the present invention. In particular, as long as there is no technical conflict, the various features in the embodiments disclosed in the present invention can be used in combination with each other in any way, and the fact that these combinations are not exhaustively described in this specification is only for the purpose of omitting space and saving resources. Therefore, the present invention is not limited to the specific embodiments disclosed herein, but includes all technical solutions that fall within the scope of the claims.

Claims

1. A slow acid system for acidizing clay shale reservoirs, characterized in that: Specifically, the slow acid system used in the acidification transformation of clay shale reservoirs simultaneously changes the contact area and effective hydrogen ion concentration, two important parameters that affect the acid-rock reaction rate, to achieve the technical requirements of high slowness; organic polycarboxylates are used to form polycarboxylic acids in the way of strong acid to weak acid, and the H is reduced through multi-stage ionization of polycarboxylic acids. + concentration, and at the same time, organic polycarboxylic acids and carboxylates are adsorbed to reservoir rocks to form an adsorption film, thereby reducing the contact area between the acid and clay minerals and reducing the acid-rock reaction rate; organic polycarboxylates can complex the metal ions in the solution to prevent them from forming metal fluorides that cause precipitation, thereby avoiding secondary damage to the reservoir; the oil washing system changes the generally strong oil-wet and weak water-wet characteristics of the original shale oil rock, and improves the fluidity of the crude oil.

2. The slow acid solution for the slow acid system according to claim 1, characterized in that: In terms of mass percentage, it includes the following components: Main acid 8-15% Organic polycarboxylates 2-5% High temperature corrosion inhibitor 1.5% Iron ion stabilizer 0.5% Clay stabilizer 0.5% Cleansing oil surfactant system 0.5%.

3. The slow acid solution for the slow acid system according to claim 2, characterized in that: The main acid solution in the slow acid solution is a medium-strong acid system such as hydrochloric acid system and phosphoric acid.

4. The slow acid solution for the slow acid system according to claim 3, characterized in that: The organic polycarboxylate in the slow acid solution is any one or two of disodium hydroxyethylene diphosphate and heptasodium diethylenetriamine pentamethylene phosphonate.

5. The slow acid solution for the slow acid system according to claim 4, characterized in that: The high temperature corrosion inhibitor in the slow acid solution is a quaternary ammonium salt corrosion inhibitor system synthesized from benzyl chloride and 3-methylpyridine or other commercially available corrosion inhibitor systems with high compatibility.

6. The slow acid solution for the slow acid system according to claim 5, characterized in that: The iron ion stabilizer in the slow acid solution is an iron ion stabilizer of an EDTAD system including an iron chelating agent.

7. The slow acid solution for the slow acid system according to claim 6, characterized in that: The clay stabilizer in the slow acid solution is a clay stabilizer including potassium chloride and a poly small cation system.

8. The slow acid solution for the slow acid system according to claim 7, characterized in that: The oil washing surfactant system in the slow acid solution is a nano non-ionic surfactant system.

9. The method for preparing a slow acid solution according to any one of claims 2 to 8, characterized in that: Weigh the main acid solution, organic polycarboxylate, high temperature corrosion inhibitor, iron ion stabilizer, clay stabilizer, washing oil surfactant system and water according to the mass percentage ratio, mix them at room temperature, shake well and let them stand for use.

10. Use of the slow-rate acid system according to claim 1 in acidizing of clay-type shale reservoirs.

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