阅读说明：本技术 一种用于开采断裂带内储集体的方法 (Method for exploiting reservoir bodies in fractured zone ) 是由 赵兵 罗攀登 李新勇 李春月 黄燕飞 房好青 张�雄 张俊江 应海玲 纪成 王立 于 2020-04-28 设计创作，主要内容包括：本发明涉及一种用于开采断裂带内储集体的方法,其步骤包括：a、在包括断裂带和完整岩石带的地质结构中构建目标井,保证其位于完整岩石带内并与储集体相邻；b、在地质结构中构造裂缝,使其将目标井与储集体连通；c、通过该目标井采集储集体内的油和/或气。本发明的用于开采断裂带内储集体的方法,可以降低断裂带内储集体的开采难度及费用,并提高目标井的采收率。(The invention relates to a method for mining a reservoir in a fracture zone, comprising the following steps: a. constructing a target well in a geological structure comprising a fractured zone and a complete rock zone, ensuring that the target well is located within the complete rock zone and adjacent to a reservoir body; b. creating a fracture in the geological structure that communicates the target well with the reservoir; c. oil and/or gas within the reservoir is collected through the target well. The method for exploiting the reservoir in the fracture zone can reduce the exploitation difficulty and cost of the reservoir in the fracture zone and improve the recovery ratio of the target well.)

1. A method for mining a reservoir within a fracture zone, comprising the steps of:

a. constructing a target well in a geological structure comprising a fractured zone and a whole rock zone, ensuring that it is within the whole rock zone and adjacent to the reservoir;

b. creating a fracture in the geological structure that places the target well in communication with a reservoir;

c. oil and/or gas within the reservoir is collected through the target well.

2. The method of claim 1 wherein in step b, the fracture is constructed by a combination of perforation and acid fracturing.

3. The method of claim 2, wherein step b comprises:

performing perforations on a portion of the target well opposite the reservoir to form the fractures of an initial formation within the geological structure;

performing a first acid fracturing on the target well to increase the aperture and length of the initial form of the fracture and form the initial form of the fracture into an intermediate form of the fracture;

the target well is acid fractured a second time, extending the ends of the fractures of the intermediate form in multiple directions within the reservoir and forming them into the fractures of the final form.

4. A method according to claim 3, wherein the acid liquor used in the first acid fracturing is a first acid liquor and the acid liquor used in the second acid fracturing is a second acid liquor, the concentration of the first acid liquor being greater than the concentration of the second acid liquor.

5. The method of claim 4, wherein the rocks within the fractured zone and the intact rock zone are both carbonate rocks.

6. The method of claim 5, wherein the first acid solution comprises, by mass, 18% -22% HCl, 0.5% -0.9% thickener, 1.0% -3.0% corrosion inhibitor, 0.5-1.5% demulsifier, and 0.5-1.5% iron ion stabilizer; the second acid liquid comprises 1.5-2.5% of cross-linking agent and 97.5-98.5% of amino acid by mass, wherein the amino acid comprises 18-22% of HCl, 0.5-0.9% of thickening agent, 2.0-4.0% of corrosion inhibitor, 0.5-1.5% of demulsifier, 0.5-1.5% of iron ion stabilizer and 0.02-0.04% of demulsifier by mass.

7. A method according to claim 6, wherein the first acid liquid and the second acid liquid have a viscosity of 36-54mPa.S and 60-80mPa.S respectively, the first acid liquid and the second acid liquid have a hydrochloric acid concentration of 20% and 20% respectively, and the first acid liquid and the second acid liquid have an injection displacement of 2-3m³Min and 6-14m³Min, the total injection amount of the first acid liquid and the second acid liquid is 80-120m respectively³And 300-600m³。

8. The method of any one of claims 2 to 7, wherein the perforations are selected from hydraulic or impulse perforations.

9. The method of any one of claims 1 to 7, wherein the shortest distance between the target well and the reservoir is 80-160 m.

10. The method according to any one of claims 1 to 7, wherein in step a, the target well is constructed in the geological structure by drilling, cementing and completing the well in sequence.

Technical Field

The invention relates to the field of oil and gas development, in particular to a method for exploiting a reservoir in a fracture zone.

Background

The fracture zone is a zone consisting of a main fault plane and broken rock blocks on both sides of the main fault plane and a plurality of secondary faults or fracture planes. Due to the strong heterogeneity of the fracture zone and the poor continuity and integrity of the rock, the unfavorable phenomena of collapse, drill sticking and the like frequently occur in the process of constructing the target well, and the mining of the reservoir in the fracture zone is a very difficult task. Even if fortunately, all difficulties are overcome and the target well is successfully constructed in the fracture zone, the stable-structure crack is difficult to construct in the fracture zone through the combination of perforation and fracturing, so that the communication between the target well and the reservoir body is not smooth and durable, and the recovery ratio of the target well is greatly reduced.

Disclosure of Invention

In order to solve all or part of the above problems, the present invention aims to provide a method for mining a reservoir in a fracture zone, which can reduce the mining difficulty and cost of the reservoir in the fracture zone and improve the recovery efficiency of a target well.

The invention provides a method for exploiting a reservoir in a fracture zone, which comprises the following steps: a. constructing a target well in a geological structure comprising a fractured zone and a whole rock zone, ensuring that it is within the whole rock zone and adjacent to the reservoir; b. creating a fracture in the geological structure that places the target well in communication with a reservoir; c. oil and/or gas within the reservoir is collected through the target well.

Further, in the step b, the fracture is constructed by means of perforation and acid fracturing.

Further, the step b comprises: performing perforations on a portion of the target well opposite the reservoir to form the fractures of an initial formation within the geological structure; performing a first acid fracturing on the target well to increase the aperture and length of the initial form of the fracture and form the initial form of the fracture into an intermediate form of the fracture; the target well is acid fractured a second time, extending the ends of the fractures of the intermediate form in multiple directions within the reservoir and forming them into the fractures of the final form.

Further, the acid solution used in the first acid pressing is a first acid solution, the acid solution used in the second acid pressing is a second acid solution, and the concentration (acid content) of the first acid solution is greater than that of the second acid solution.

Further, the rocks within the fractured zone and the intact rock zone both belong to carbonate rock.

Further, the first acid solution comprises 18-22% of HCl, 0.5-0.9% of thickening agent, 1.0-3.0% of corrosion inhibitor, 0.5-1.5% of demulsifier and 0.5-1.5% of iron ion stabilizer by mass; the second acid solution comprises 18-22% of HCL, 0.5-0.9% of thickening agent, 2.0-4.0% of corrosion inhibitor, 0.5-1.5% of demulsifier, 0.5-1.5% of iron ion stabilizer and 0.02-0.04% of demulsifier by mass, and further comprises a cross-linking agent, wherein the cross-linking ratio is 100: (1.5-2.5).

Further, the viscosity of the first acid liquid and the viscosity of the second acid liquid are respectively 36-54mPa.S and 60-80mPa.S, the hydrochloric acid concentration of the first acid liquid and the hydrochloric acid concentration of the second acid liquid are respectively 20% and 20%, and the injection displacement of the first acid liquid and the injection displacement of the second acid liquid are respectively 2-3m³Min and 6-14m³Min, the total injection amount of the first acid liquid and the second acid liquid is 80-120m respectively³And 300-600m³。

Further, the perforation is selected from water conservancy perforation or pulse perforation.

Further, the shortest distance between the target well and the reservoir is 80-160 m.

Further, in step a, a target well is constructed in the geological structure by means of drilling, cementing and completing the well in sequence.

According to the method for exploiting the reservoir in the fractured zone, the target well is not formed in the fractured zone, but is formed in the complete rock zone adjacent to the reservoir in the fractured zone, and because the continuity and the integrity of the complete rock zone are far higher than the same properties of the fractured zone, the method can effectively reduce the occurrence probability of collapse, sticking and other adverse phenomena in the process of constructing the target well, and further effectively reduce the exploitation difficulty and the cost of the reservoir in the fractured zone. Meanwhile, the method constructs the cracks by replacing a perforation and fracturing combined mode with a perforation and acid fracturing combined mode, so that the structural stability of the cracks is effectively improved, the communication between the target well and the reservoir body is smoother and more durable, and the recovery ratio of the target well can be improved. Because the method implements acid fracturing for at least two times, the tail end of the crack extends in different directions in the reservoir body, the communication between the target well and the reservoir body can be ensured to be smoother, and the target well is facilitated to be communicated with the reservoir body near the fracture zone, so that the recovery ratio of the target well can be further improved.

Drawings

Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. In the figure:

FIG. 1 shows a flow diagram of a method for mining a reservoir within a fracture zone in accordance with an embodiment of the present invention.

In the drawings, like parts are provided with like reference numerals. The figures are not drawn to scale.

Detailed description of the preferred embodiment

The invention will be further explained with reference to the drawings.

FIG. 1 shows a flow diagram of a method for mining a reservoir within a fracture zone in accordance with an embodiment of the present invention. As shown in fig. 1, a method for mining a reservoir within a fracture zone includes: step a, constructing a target well in a geological structure comprising a fracture zone and a complete rock zone, and ensuring that the target well is positioned in the complete rock zone and is adjacent to a reservoir body (namely, the distance is less than or equal to 160 m); b, constructing cracks in the geological structure to enable the cracks to communicate the target well with the reservoir body; and c, collecting oil and/or gas in the reservoir through the target well.

According to the method for mining the reservoir in the fracture zone, the target well is not formed in the fracture zone, but is formed in the complete rock zone adjacent to the reservoir in the fracture zone, and because the continuity and the integrity of the complete rock zone are far higher than the same properties of the fracture zone, the method can effectively reduce the occurrence probability of collapse, stuck drill and other unfavorable phenomena in the process of constructing the target well, and further effectively reduce the mining difficulty and the mining cost of the reservoir in the fracture zone.

It should be noted that the construction cost of the fracture is closely related to the length of the fracture, and the construction cost thereof will increase significantly with the increase of the length, which in severe cases leads to the late-stage yield value of the target well not to exceed the construction cost of the fracture, so in order to ensure the higher economic benefit of the target well, the shortest distance between the target well and the reservoir is recommended to be selected to be 80-160m, so as to reduce the length and cost of the required fracture and improve the economic benefit of the target well.

In order to increase the reliability of the target well, it is proposed in step a to construct the target well in the geological structure by means of technically sophisticated drilling, cementing and completion.

The inventor of the present application finds that, in the prior art, cracks are constructed in a fracture zone through a combination of perforation and fracturing, and although complex cracks can be formed in this way, the stability of rock fragments around the cracks is seriously damaged due to the overlarge pressure of the fracturing, so that the rock fragments are easy to collapse during the process of conveying oil and/or gas to fill a part of the cracks, and further, the recovery rate of a target well is reduced. This example, in order to increase the recovery of the target well, in step b, fractures are constructed in the geological structure by a combination of perforation and acid fracturing instead of a combination of perforation and fracturing. Because the pressure of acid fracturing is far lower than the pressure of fracturing, the damage to the stability of rock fragments around the fracture is lighter, so that the structural stability of the fracture is effectively improved, the communication between the target well and the reservoir body is ensured to be smoother and more durable, and the recovery ratio of the target well is further improved. The perforations may be selected from hydraulic or impulse perforations, but preferably impulse perforations are recommended to further reduce their extent of damage to the stability of the rock fragments surrounding the fracture.

In order to further increase the recovery factor of the target well, step b may specifically comprise: perforating a portion of the target well opposite the reservoir to form an initial form of fractures within the geological structure; performing first acid fracturing on the target well to increase the aperture and the length of the initial form fracture and form the initial form fracture into an intermediate form fracture; the target well is acid fractured a second time, extending the ends of the intermediate form fractures in multiple directions within the reservoir and forming them into final form fractures. Because the method is implemented for acid fracturing at least twice, the tail end (the end far away from the target well) of the crack extends in different directions in the reservoir body, the communication between the target well and the reservoir body can be ensured to be smoother, the target well is facilitated to be communicated with the reservoir body near the fracture zone, and the recovery ratio of the target well can be further improved.

The acid solution used in the first acid pressing is a first acid solution, and the acid solution used in the second acid pressing is a second acid solution, wherein the concentration of the first acid solution is preferably greater than that of the second acid solution. The high-concentration first acid liquid is used for forming a short and thick single main section in the crack, and the low-concentration second acid liquid is used for forming a plurality of slender branch sections in the crack, so that the single main section can effectively receive oil and/or gas from each branch, and the purpose of balancing the conduction capacity of each section of the crack is achieved.

By carrying out the experiment of the present example in carbonate geology (i.e. the rocks in the fracture zone and the intact rock zone both belong to carbonate rock), it is known that when the viscosities of the first acid solution and the second acid solution are 36-54mpa.s and 60-80mpa.s, respectively, the hydrochloric acid concentrations of the first acid solution and the second acid solution are 20% and 20%, respectively, and the injection displacement amounts of the first acid solution and the second acid solution are 2-3m, respectively³Min and 6-14m³Min, and the total injection amount of the first acid solution and the second acid solution is 80-120m³And 300-600m³And the structure of the crack is similar to the expected shape and is stable, so that the communication between the target well and the reservoir body can be smoother and more durable, and the recovery ratio of the target well is remarkably improved. Wherein the first acid liquid comprises 18-22% of HCl, 0.5-0.9% of thickening agent, 1.0-3.0% of corrosion inhibitor, 0.5-1.5% of demulsifier and 0.5-1.5% of iron ion stabilizer by mass. The second acid liquid comprises 1.5-2.5% of cross-linking agent and 97.5-98.5% of amino acid by mass, and the amino acid comprises 18-22% of HCl, 0.5-0.9% of thickening agent, 2.0-4.0% of corrosion inhibitor, 0.5-1.5% of demulsifier, 0.5-1.5% of iron ion stabilizer and 0.02-0.04% of demulsifier by mass.

It should be noted that, this embodiment may be implemented in carbonate geology, and may also achieve similar effects in geology of other lithologies, but when implemented in geology of other lithologies, it is necessary to adjust the composition, form, injection displacement, total injection amount, and the like of the first acid liquid and the second acid liquid according to actual conditions. Since this adjustment is conventional in the art, it will not be described in detail for the sake of brevity.

In summary, the method for mining the reservoir in the fracture zone according to the embodiment of the invention can reduce the mining difficulty and cost of the reservoir in the fracture zone and improve the recovery ratio of the target well.

The above description is only a preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily make changes or variations within the technical scope of the present invention disclosed, and such changes or variations should be covered within the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims. The features mentioned in the embodiments can be combined in any manner as long as there is no conflict. It is intended that the invention not be limited to the particular embodiments disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.