Deployment and adjustment method for CO2 injection development well pattern in new area of ultra-low permeability reservoir

Abstract

The invention discloses a method for deploying and adjusting a CO2 injection development well pattern in a new area of an ultra-low permeability reservoir, which comprises the following steps of: deploying a basic well pattern, forming a gas injection well positioned in the center and producing wells surrounding the gas injection well, and injecting the gas injection well, so that the problem of difficulty in water injection is solved through CO2 gas injection, and the CO2 gas injection efficiency is improved. After the basic well pattern is deployed, when the gasoline ratio of the first five-point method well pattern changes suddenly or the stratum energy reaches 120%, the side wells of the oil production wells of the square well pattern are opened, injection is continuously carried out on the gas injection well, and when the corner wells of the oil production wells of the square well pattern reach gas channeling, injection is continuously carried out on the gas injection well; according to the well pattern deployment and adjustment method, the production well corner wells of the square well pattern are converted into the gas injection wells, the production efficiency is guaranteed, the stability of the stratum is guaranteed, CO2 is injected in the new production and construction area of the ultra-low permeability reservoir for displacement development, and compared with traditional well pattern development, the recovery efficiency is improved by 7.3%, and the gas channeling time is delayed by 3.2 years through the well pattern deployment and adjustment method.

Description

Technical Field

[0001] The invention relates to the technical field of oilfield exploitation, and in particular to a method for deploying and adjusting a CO2 injection development well pattern in a new area of ​​an ultra-low permeability oil reservoir. Background Art

[0002] With the exhaustion of conventional oil fields, the goal of oil production has gradually focused on the development of unconventional oil fields (object). As one of the types of unconventional oil fields, ultra-low permeability reservoirs have the characteristics of low reservoir porosity, low permeability, poor natural flow capacity of the bottom fluid, large seepage resistance, low single well production capacity, rapid production decline, and poor stable production capacity. Its exhaustion production capacity and water injection effect are extremely poor. Therefore, CO2 injection development plays an important role in achieving efficient development of unconventional oil fields (problems, necessity). Through the characteristics of CO2's good injectability, easy miscibility, expansion of crude oil, reduction of viscosity, and extraction of light components (principle), the use of CO2 injection development can supplement formation energy, sweep residual oil areas, and achieve a significant increase in crude oil recovery. It is currently the most advantageous gas injection technology for oil recovery.

[0003] At present, the development of new ultra-low permeability oil reservoirs usually adopts the development methods of depletion exploitation, water injection, or initial depletion and mid-to-late water injection. Due to the reservoir characteristics of ultra-low permeability oil reservoirs, conventional development methods often have the following problems: 1. The reservoir pressure coefficient is low, the natural energy is insufficient, the production of depletion exploitation decreases rapidly, and the production decline rate is high in the early stage of development; 2. Water injection is difficult. After water injection, the pressure of some oil reservoirs increases, micro-cracks in the formation open, water seepage occurs between the injection and production wells, and the effect of replenishing formation energy is limited. Summary of the invention

[0004] The purpose of the present invention is to provide a method for deployment and adjustment of CO2 injection development well network in new ultra-low permeability oil reservoir areas, so as to overcome the problems in the prior art such as difficulty in water injection, low reservoir pressure coefficient, insufficient natural energy, rapid decline in production due to depletion exploitation, and high production decline rate in the early stage of development.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] A method for deploying and adjusting a CO2 injection development well pattern in a new ultra-low permeability reservoir area, comprising:

[0007] Calculating the optimal well spacing of the basic well network and deploying the basic well network, wherein the basic well network includes at least one square well network, wherein the square well network includes a gas injection well located in the center and oil production wells arranged around the gas injection well, wherein the oil production wells include oil production well side wells and oil production well corner wells;

[0008] The gas injection wells are injected, and the corner wells of the oil production wells in the square well pattern are opened to form the first five-point method well pattern;

[0009] Continue to inject gas into the gas injection wells. When the gasoline ratio of the first five-point well pattern changes suddenly or the formation energy reaches 120%, open the oil production well side wells of the square well pattern.

[0010] Continue to inject gas into the gas injection wells. When the corner wells of the oil production wells in the square well network reach gas breakthrough, the corner wells of the oil production wells in the square well network are converted into gas injection wells to form a second five-point method well network.

[0011] Preferably, the well spacing ratio of the basic well pattern, the first five-point method well pattern and the second five-point method well pattern is

[0012] Preferably, the well spacing of the basic well pattern is determined according to the well pattern density.

[0013] Preferably, the formula for determining the well pattern density is:

[0014] NR T PE D Be B / S =[M(1+i) T / 2 +TC]AS 2

[0015] Where N is geological reserves; R T is the extent of recoverable reserves during the development period; P is the crude oil sales price; E D is the oil recovery efficiency; B is the well network index; S is the well network density; A is the oil-bearing area; M is the total investment in a single well; i is the loan interest; T is the investment recovery period; C is the operating cost; and e is a natural constant.

[0016] Preferably, the best well spacing is:

[0017]

[0018] Where S is the well pattern density and L is the optimal well spacing.

[0019] Preferably, the gas injection well continuously injects gas throughout the process.

[0020] Preferably, the ratio of the number of gas injection wells to the number of oil production wells in the basic well network is 1:3.

[0021] Preferably, the ratio of the number of gas injection wells to the number of oil production wells in the first five-point method well network is 1:1.

[0022] Preferably, the gas channeling standard is a gas-oil ratio of 1500m 3 / t.

[0023] Preferably, the opening of the remaining wells of the first five-spot method well pattern is determined according to the gas-oil ratio of the reservoir blocks in the well pattern and the formation pressure level factors.

[0024] Compared with the prior art, the present invention has the following beneficial effects: the present invention provides a method for deploying and adjusting a CO2 injection development well network in a new area of ​​an ultra-low permeability oil reservoir, by deploying a basic well network, forming a gas injection well located in the center and oil production wells arranged around the gas injection well, and then injecting gas into the gas injection well, and the injection of CO2 gas solves the problem of water injection difficulties without affecting the changes in the structure within the formation, and after the basic well network is deployed, the switch state and shape of the oil production well are changed according to the injection situation of the gas injection well, thereby ensuring the mining efficiency and the stability of the formation. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a flow chart of a method for deploying and adjusting a CO2 injection development well pattern in a new ultra-low permeability reservoir area according to the present invention;

[0026] Figure 2 The basic well network deployed in the embodiment;

[0027] Figure 3 The first five-point well network deployed in the embodiment;

[0028] Figure 4 The first five-point method well pattern for opening the oil production well side well in the embodiment;

[0029] Figure 5 This is the second five-point well network deployed in the embodiment. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0031] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0033] In the description of the embodiments of the present invention, it should be noted that if the terms "upper", "lower", "horizontal", "inner", etc. indicate an orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the product of the invention is usually placed when in use, it is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, the terms "first", "second", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0034] In addition, if the term "horizontal" appears, it does not mean that the component must be absolutely horizontal, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", which does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0035] In the description of the embodiments of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal connection of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0036] The present invention is further described in detail below in conjunction with the accompanying drawings:

[0037] like Figure 1 As shown, the present invention provides a method for deploying and adjusting a CO2 injection development well pattern in a new area of ​​an ultra-low permeability oil reservoir, comprising:

[0038] S101 calculates the optimal well spacing of a basic well pattern and deploys the basic well pattern, wherein the basic well pattern includes at least one square well pattern, wherein the square well pattern includes a gas injection well located in the center and oil production wells arranged around the gas injection well, wherein the oil production wells include oil production well side wells and oil production well corner wells;

[0039] S102 injects gas into the gas injection wells, opens the corner wells of the oil production wells in the square well pattern, and forms the first five-point method well pattern;

[0040] S103 continues to inject gas into the gas injection wells, and when the gasoline ratio of the first five-point method well pattern suddenly changes or the formation energy reaches 120%, the oil production well side wells of the square well pattern are opened;

[0041] S104 continues to inject gas into the gas injection wells, and when the corner wells of the oil production wells in the square well pattern reach gas breakthrough, the corner wells of the oil production wells in the square well pattern are converted into gas injection wells to form a second five-point method well pattern.

[0042] The well spacing ratio of the basic well network, the first five-point method well network and the second five-point method well network is 1:√2:1.

[0043] The well spacing of the basic well network is determined according to the well network density.

[0044] The formula for determining the well pattern density is:

[0045] NR T PE D Be B / S =[M(1+i) T / 2 +TC]AS 2

[0046] Where N is geological reserves; R T is the extent of recoverable reserves during the development period; P is the crude oil sales price; E D is the oil recovery efficiency; B is the well network index; S is the well network density; A is the oil-bearing area; M is the total investment in a single well; i is the loan interest; T is the investment recovery period; C is the operating cost; and e is a natural constant.

[0047] The best well spacing is:

[0048]

[0049] Where S is the well pattern density and L is the optimal well spacing.

[0050] The gas injection wells continuously inject gas throughout the process.

[0051] The ratio of gas injection wells to oil production wells in the basic well network is 1:3.

[0052] In the first five-point method well network, the ratio of gas injection wells to oil production wells is 1:1.

[0053] The standard for gas breakthrough is a gas-oil ratio of 1500m3 / t.

[0054] The opening of the remaining wells in the first five-point method well network is determined based on the gas-oil ratio of the reservoir block in the well network and the formation pressure level factors.

[0055] Example:

[0056] Step S1: deploy a basic well pattern a, wherein the basic well pattern a includes at least one well spacing of A square well pattern 1 includes a gas injection well 1 in the center and oil production wells 2 arranged around the gas injection well 1. At this time, the well pattern spacing is L×2L. In order to avoid the increase of well control risk due to high gas-oil ratio and high formation pressure in the late stage of gas injection, all deployed wells are implemented synchronously, which is a one-time deployment of the well pattern.

[0057] Step S2: Based on the fact that the CO2 injection capacity is 1.5 to 3 times the water injection capacity, after the gas injection wells are injected, the four corner wells 21 in the basic well pattern a are opened first (the four side wells 22 are in the closed state), forming a well spacing of The first five-point well pattern b.

[0058] Step S3: After the first five-point well network b has been developed for a period of time (including but not limited to ① when the gas-oil ratio suddenly changes: if the well network is not adjusted, the risk of reservoir gas channeling increases; ② the formation energy reaches 120%: the formation energy remains at a high level, if the well network is not adjusted to reduce the injection-production ratio, the risk of formation fracture opening increases), the side well 22 of the square basic well network a is opened, so that all injection and production wells are opened, forming a square well network with a well spacing of L×2L.

[0059] Step S4: deploy the second five-point well pattern c. When the oil production wells of the first square well pattern a reach gas breakthrough (gas-oil ratio reaches 1500m 3 / t, the oil change ratio decreases and continued development is no longer economically beneficial), and the four oil production corner wells 21 of the first square well pattern a are converted into gas injection wells 211 to form a second five-point method well pattern c.

[0060] Specifically, in step S1, if Figure 2 As shown, 4 square well network injection and production units are drawn. Of course, the basic well network a is not limited to having 4 square well networks, and can also be other numbers, such as 1, 2 or more square well networks 1, which are not limited here. In this embodiment, the square well network 1 is defined in the form of central gas injection and surrounding oil production, that is, the square well network 1 includes a gas injection well 1 located in the center and 4 oil production corner wells 21 and 4 oil production side wells 22 arranged around the gas injection well 1. Two adjacent square well networks 1 in the basic well network a share 2 gas injection wells 11 and 1 oil production corner well 21 located on the same side. The ratio of the number of gas injection wells to oil production wells in the basic well network a is 1:3.

[0061] In step S2, if Figure 3 As shown, the four oil production corner wells 21 in the square well pattern in the basic well pattern a are opened to form the first five-point method well pattern b. The block is put into development with the first five-point method well pattern b, the injection and production well spacing of the first five-point method well pattern b is 2L, and the ratio of the number of gas injection wells to oil production wells is 1:1.

[0062] In step S3, if Figure 4 As shown, after the first five-point well pattern b has produced for a predetermined time, the four production side wells 22 in the square well pattern 1 in the basic well pattern a are opened so that all wells in the basic well pattern a are opened. The opening timing of the remaining wells in the first five-point well pattern b is determined according to factors such as the gas-oil ratio of the reservoir block and the formation pressure level.

[0063] In step S4, as Figure 5 , when the gas-oil ratio of each oil production well in the first square well pattern c reaches 1500 m 3 / t (judging gas channeling in the reservoir), convert 4 oil production corner wells 21 of the basic well pattern a into gas injection wells 211 to form a second five-spot well pattern d.

[0064] In the embodiment of the present invention, the well spacing of the basic well pattern is determined according to the well pattern density.

[0065] For the optimal well spacing, it is determined according to the well pattern density, and the well pattern density can be obtained according to the following formula:

[0066] NR T PE D Be B / S =[M(1 + i) T / 2 +TC]AS 2

[0067] In the formula:

[0068] N: Geological reserves, 10 4 t;

[0069] R T : Recovery factor of recoverable reserves during the development period, f;

[0070] P: Crude oil selling price, yuan / t;

[0071] E D : Oil displacement efficiency, f;

[0072] B: Well pattern index, km 2 / well;

[0073] S: Well pattern density, wells / km 2 ;

[0074] A: Oil-bearing area, km 2 ;

[0075] M: Total investment per well, 10 4 yuan / well;

[0076] i: Loan interest, f;

[0077] T: Investment payback period, a;

[0078] C: Operating cost, 10 4 yuan / (well·a);

[0079] e: Natural constant, whose value is approximately 2.71828.

[0080] After obtaining the well pattern density S, the optimal well spacing is obtained according to the following formula:

[0081]

[0082] Where: L: optimal well spacing, m.

[0083] In the embodiment of the present invention, the well spacing of the basic well pattern a is 2L, and the well spacing of the first five-point method well pattern b is The second five-point method well spacing is 2L.

[0084] In the present invention, Figure 1 In the embodiment shown, the dynamic well network is developed in a continuous gas injection manner, that is, during the entire dynamic well network deployment method, each gas injection well 1, gas injection well 11 and gas injection well 211 is in a state of continuous CO2 injection.

[0085] In the new production area of ​​ultra-low permeability oil reservoir, CO2 injection displacement development is carried out. The well network deployment and adjustment method described in this method can increase the recovery rate by 7.3% and delay the gas breakthrough time by 3.2 years compared with the traditional well network development.

[0086] Although the embodiments of the present invention are described above in conjunction with the accompanying drawings, the present invention is not limited to the above-mentioned specific embodiments and application fields, and the above-mentioned specific embodiments are only illustrative and instructive, rather than restrictive. Under the guidance of the specification, a person skilled in the art can also make many forms without departing from the scope of protection of the claims of the present invention, all of which belong to the scope of protection of the present invention.

Claims

1. A method for deploying and adjusting a CO2 injection development well pattern in a new ultra-low permeability reservoir, characterized in that: include: Calculating the optimal well spacing of the basic well network and deploying the basic well network, wherein the basic well network includes at least one square well network, wherein the square well network includes a gas injection well located in the center and oil production wells arranged around the gas injection well, wherein the oil production wells include oil production well side wells and oil production well corner wells; The gas injection wells are injected, and the corner wells of the oil production wells in the square well pattern are opened to form the first five-point method well pattern; Continue to inject gas into the gas injection wells. When the gasoline ratio of the first five-point well pattern changes suddenly or the formation energy reaches 120%, open the side wells of the oil production wells in the square well pattern. Continue to inject gas into the gas injection wells. When the corner wells of the oil production wells in the square well network reach gas breakthrough, the corner wells of the oil production wells in the square well network are converted into gas injection wells to form a second five-point method well network.

2. The method for deployment and adjustment of CO2 injection development well pattern in new ultra-low permeability reservoir area according to claim 1, characterized in that: The well spacing ratio of the basic well pattern, the first five-point method well pattern and the second five-point method well pattern is 1:

1.

3. The method for deployment and adjustment of CO2 injection development well pattern in new ultra-low permeability reservoir area according to claim 1, characterized in that: The well spacing of the basic well network is determined according to the well network density.

4. The method for deployment and adjustment of CO2 injection development well pattern in new ultra-low permeability reservoir area according to claim 3, characterized in that: The formula for determining the well pattern density is: NR T PE D Be B / S =[M(1+i) T / 2 +TC]AS 2 Where N is geological reserves; R T is the extent of recoverable reserves during the development period; P is the crude oil sales price; E D is the oil recovery efficiency; B is the well network index; S is the well network density; A is the oil-bearing area; M is the total investment in a single well; i is the loan interest; T is the investment recovery period; C is the operating cost; and e is a natural constant.

5. The method for deployment and adjustment of CO2 injection development well pattern in new ultra-low permeability reservoir area according to claim 4, characterized in that: The optimal well spacing is: Where S is the well pattern density and L is the optimal well spacing.

6. The method for deployment and adjustment of CO2 injection development well pattern in new ultra-low permeability reservoir area according to claim 1, characterized in that: The gas injection well continuously injects gas during the whole process.

7. The method for deployment and adjustment of CO2 injection development well pattern in new ultra-low permeability reservoir area according to claim 1, characterized in that: The ratio of the number of gas injection wells to the number of oil production wells in the basic well network is 1:

3.

8. The method for deployment and adjustment of CO2 injection development well pattern in new ultra-low permeability reservoir area according to claim 1, characterized in that: In the first five-point method well network, the ratio of gas injection wells to oil production wells is 1:

1.

9. The method for deployment and adjustment of CO2 injection development well pattern in new ultra-low permeability reservoir area according to claim 1, characterized in that: The standard for gas channeling is that the gas-oil ratio reaches 1500m 3 / t.

10. The method for deployment and adjustment of CO2 injection development well pattern in new ultra-low permeability reservoir area according to claim 1, characterized in that: The opening of the remaining wells in the first five-point method well network is determined based on the gas-oil ratio of the reservoir block in the well network and the formation pressure level factors.

Images