Crude oil development method and device for fractured-porous oil reservoir

Abstract

The invention discloses a crude oil development method for a fractured-porous oil reservoir, which comprises the following steps: injecting air into an injection well, and carrying out an oxidation exothermic reaction by using the air and a mixture of injected in-situ crude oil, an oxygen-consuming agent and a catalyst; closing the production well, and forming a hot gas cavity around the injection well based on the heat of the oxidation exothermic reaction; on the basis of the hot air cavity, micro cracks are formed by crack-pore type oil reservoir matrix reservoir rock, and matrix crude oil expands to enter a crack system; based on the crack system, crude oil converges to form an oil wall; and the production well is opened, air is continuously injected into the injection well, and production is stable. According to the method, an air injection hot mixed phase technology is adopted, air is continuously injected into an oil layer to generate high-temperature thermal oxidation, the mixed phase pressure of generated mixed phase gas is greatly reduced under the high-temperature condition, hot mixed phase of the mixed phase gas and liquid-phase crude oil is achieved, interfacial tension is eliminated, the capillary force effect is overcome, and matrix pore crude oil is effectively utilized.

Description

Technical Field

[0001] The present invention relates to the technical field of air injection development, and in particular to a method and device for developing crude oil in a fracture-pore type oil reservoir. Background Art

[0002] Fracture-pore reservoirs, characterized by large reserves and high production, are one of the primary reservoir types found in today's high-yield, large oil fields. Fractures are extensively developed in fracture-pore reservoirs, with matrix pores and fractures serving as the primary reservoir spaces, and fractures as the primary seepage pathways. Due to the significant disparity in seepage capacity between fractures and matrix pores, during reservoir development, crude oil in fractures is produced first, leaving crude oil in matrix pores as residual oil, which is difficult to mobilize. Therefore, effectively utilizing the residual oil in the matrix is ​​key to improving the recovery efficiency of fracture-pore reservoirs.

[0003] Water and gas injection are the primary methods for increasing the recovery of fractured-porous reservoirs. Conventional water flooding can only displace residual oil in the fractures, while capillary forces hinder the recovery of crude oil in the matrix pores. Using surfactants to reduce the oil-water interfacial tension can effectively increase the recovery rate of matrix crude oil, but current research is limited to laboratory studies and limited field trials, and the high cost hinders industrial application. Gas injection generally involves immiscible and miscible flooding. In immiscible flooding, the high permeability difference between the fracture and matrix system leads to high gas channeling within the fractures, and the injected gas is typically a non-wetting phase, making it difficult to recover the residual matrix oil. Capillary forces are the primary factor hindering the recovery of matrix crude oil. Miscible flooding can eliminate interfacial tension, overcome capillary forces, and prevent re-imbibition of crude oil into the matrix pores during seepage, thus effectively recovering the matrix crude oil. However, the high miscibility pressure of crude oil in most reservoirs in my country makes it difficult to achieve miscibility. Furthermore, the high cost of injection media and the scarcity of gas sources hinder the large-scale application of this technology. Therefore, it is urgent to find new technologies to improve the development effect of fracture-pore reservoirs. Summary of the Invention

[0004] The purpose of the present invention is to provide a method and device for developing crude oil in a fracture-pore type oil reservoir to solve the above technical problems.

[0005] To achieve the above object, the present invention provides a method for developing crude oil in a fracture-pore type reservoir, the method comprising:

[0006] Injecting air into the injection well, and utilizing the mixture of air, injected formation crude oil, oxygen consuming agent and catalyst to carry out an oxidative exothermic reaction;

[0007] The production well is shut down, and a hot gas cavity is formed around the injection well due to the heat of the oxidation exothermic reaction;

[0008] Based on the hot gas cavity, micro-fractures are formed in the matrix reservoir rock of the fracture-pore type oil reservoir, and the matrix crude oil expands into the fracture system;

[0009] Based on the fracture system, crude oil gathers to form an oil wall;

[0010] The production wells are opened, air is continuously injected into the injection wells, and the production wells produce stably.

[0011] The present invention also provides a crude oil development device for a fracture-pore type oil reservoir, the device comprising:

[0012] A reaction unit is used to inject air into the injection well and utilize the mixture of the air, the injected formation crude oil, the oxygen consuming agent and the catalyst to perform an exothermic oxidation reaction;

[0013] A shut-in unit for shutting down the production well, forming a hot gas cavity around the injection well based on the heat of the oxidation exothermic reaction;

[0014] A formation unit for forming micro-fractures in matrix reservoir rocks of fracture-pore type oil reservoirs based on hot gas cavities, and for expanding matrix crude oil into the fracture system;

[0015] Convergence unit, used for crude oil convergence to form oil wall based on fracture system;

[0016] The production unit is used to open the production well, continuously inject air into the injection well, and ensure stable production of the production well.

[0017] Technical effects and advantages of the present invention:

[0018] 1. The present invention adopts air injection hot miscibility technology. By continuously injecting air into the oil layer to cause high-temperature thermal oxidation, the miscibility pressure of the generated miscible gas is greatly reduced under high temperature conditions, achieving hot miscibility with the liquid crude oil, eliminating interfacial tension, overcoming the capillary force effect, and effectively utilizing the crude oil in the matrix pores.

[0019] 2. The injection medium air in air hot mixed phase development has a wide range of sources and does not require medium costs, avoiding the problem of high medium costs in conventional gas injection development that makes it difficult to apply on a large scale. In addition, the on-site operation method is simple, with low operating costs, high development efficiency and a wide range of applications.

[0020] 3. Air-injection miscible flooding technology has successfully been field tested, achieving a significant technological breakthrough. Applying air-injection miscible flooding technology to the development of fractured-porous reservoirs is expected to become a key means of significantly increasing production and recovery in these reservoirs.

[0021] Other features and advantages of the present invention will be described in the following description, and in part will become apparent from the description, or will be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Flow chart of crude oil development method for fracture-pore reservoirs. DETAILED DESCRIPTION

[0023] The following will clearly and completely describe the technical solution of the present invention in conjunction with the accompanying drawings provided by the present invention. Moreover, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0024] It should be noted that the structures, proportions, sizes, etc. illustrated in the drawings of this specification are only used to match the contents disclosed in the specification for understanding and reading by those familiar with this technology, and are not used to limit the conditions for implementation of the present invention. Therefore, they have no substantial technical significance. Any modification of the structure, change in the proportional relationship, or adjustment of the size should still fall within the scope of the technical content disclosed by the present invention without affecting the efficacy and purpose that can be achieved by the present invention. At the same time, terms such as "upper", "lower", "left", "right", "middle" and "one" quoted in this specification are only for the convenience of description and are not used to limit the scope of implementation of the present invention. Changes or adjustments in their relative relationships should also be regarded as the scope of implementation of the present invention without substantially changing the technical content.

[0025] To address the deficiencies of the prior art, the present invention discloses a method for developing crude oil in a fracture-pore type oil reservoir. The method comprises: injecting air into an injection well, and utilizing a mixture of the air and the injected formation crude oil, an oxygen consuming agent, and a catalyst to undergo an exothermic oxidation reaction; closing a production well, and forming a hot gas cavity around the injection well based on the heat of the exothermic oxidation reaction; microcracks are formed in the matrix reservoir rock of the fracture-pore type oil reservoir due to the hot gas cavity, and the matrix crude oil expands into the fracture system; based on the fracture system, the crude oil converges to form an oil wall; and opening a production well, continuously injecting air into the injection well, and achieving stable production at the production well.

[0026] This method includes three main development stages: hot miscible phase startup, asynchronous injection and production to create an oil wall, and stable production of production wells. Hot miscible phase startup is achieved by sequentially injecting formation crude oil, catalyst + oxygen consuming agent, hot foam liquid, and finally air. Through the asynchronous injection and production development mode, a hot gas cavity is formed in the near-wellbore area of ​​the gas injection well, establishing a hot miscible phase state. The matrix crude oil expands and self-drives into the fracture system to form an oil wall, effectively suppressing gas channeling, effectively mobilizing the remaining oil in the matrix of the fracture-pore type reservoir, and significantly improving the recovery rate of the fracture-pore type reservoir.

[0027] In order to better explain this solution, the following Figure 1 A method for obtaining crude oil from a fracture-pore type reservoir is explained in detail.

[0028] 1. Inject air into the injection well and use the mixture of air, injected formation crude oil, oxygen consuming agent and catalyst to carry out oxidation exothermic reaction.

[0029] Specifically, it includes: targeted selection of fracture-porous reservoirs suitable for air injection development, reservoir pressure>15MPa, oil layer thickness>10m, and oil saturation>30%.

[0030] Inject a slug of crude oil into the injection well to increase the oil saturation in the area near the wellbore. The injection volume is (1-1.5)×hm 3 ; Then inject oxygen consuming agent + catalyst (wt1~5%) slug, the injection amount is (0.2~0.5)×hm 3 ; then inject (1~1.5)×hm 3 Hot foam is used to clean the wellbore, ensuring that no residual oil (formation crude oil, oxygen consuming agent + catalyst) remains on the wellbore wall and pushing the formation crude oil and oxygen consuming agent deep into the formation. Where h is the perforation height.

[0031] Then inject air at a high speed of (1500~2500)×h Nm 3 / d, air is mixed with the front slug (formation crude oil, oxygen consuming agent and catalyst) and oxidation heat is released by the formation temperature (>50℃) to achieve hot miscible startup.

[0032] 2. The production well is closed, and a hot gas cavity is formed around the injection well based on the heat of the oxidation exothermic reaction.

[0033] 3. Based on the hot gas cavity, micro-cracks are formed in the matrix reservoir rock of the fracture-pore type oil reservoir, and the matrix crude oil expands into the fracture system.

[0034] 4. Based on the fracture system, crude oil gathers to form an oil wall.

[0035] 5. Open the production wells, continuously inject air into the injection wells, and ensure stable production in the production wells.

[0036] Specifically, after continuous air injection into the injection wells, production wells in the first-line well group are temporarily shut down to prevent rapid gas channeling along the fractures. Pressure and temperature changes in the production wells are closely monitored to assess the thermal oxidation state. During this process, a hot gas cavity forms within 5 meters of the injection wellbore. The high temperature improves the matrix reservoir properties and forms microfractures. The crude oil in the matrix pores mixes with the generated miscible gas, eliminating interfacial tension. Simultaneously, the thermal expansion of the matrix crude oil creates a self-propelled expansion, allowing the crude oil in the matrix pores to seep into the fracture system and accumulate, forming an oil wall. This effectively suppresses gas channeling and establishes a stable thermal oxidation front. This process effectively increases formation pressure and inhibits bottom water coning.

[0037] The method further comprises: when the air is injected continuously for 30 to 90 days, the cumulative air injection is (90,000 to 150,000)×hNm 3 After that, the production wells are opened for production and the injection rate of the gas injection wells is adjusted to (1000~1500)×h Nm 3 During the initial opening of a production well, liquid production is controlled at the level before shutting in. Once production stabilizes, the liquid rate is gradually increased. A monitoring system is established to monitor changes in gas production and gas composition in real time, allowing for timely adjustments to the liquid production level of the production well to maintain stable production.

[0038] In order to better explain the present invention, examples are provided below.

[0039] Based on the basic geological reservoir parameters of a fracture-pore reservoir block in the Liaohe Oilfield, a dual-permeability numerical simulation theoretical model was established and numerical simulation research was carried out. The reservoir has an average burial depth of 2950m, an oil-bearing amplitude of 480m, an effective oil layer thickness of 127m, a formation temperature of 101°C, a matrix permeability of 1-10mD, a fracture permeability of 290mD, a current formation pressure of approximately 17MPa, a recovery rate of 31%, and a perforation thickness of 50m.

[0040] The specific steps are as follows:

[0041] 1. Carry out historical matching with a fitting accuracy of more than 95% to obtain the current three-field distribution numerical simulation model of the reservoir;

[0042] 2. The production wells are shut down, and the injection wells inject 50m3 of formation crude oil in sequence. 3 , catalyst + oxygen consuming agent 10m 3 , hot foam agent 50m 3 ;

[0043] 3. Then continuously inject air at a speed of 50000Nm 3 / d, gas injection for 90 days, cumulative gas injection 450×10 4 Nm 3 ,In the numerical simulation model, a hot gas cavity is formed in the near-wellbore area with a temperature of 200-320°C, and a stable oil wall is formed in the fracture system;

[0044] 4. Production wells were put into production, the thermal oxidation front advanced steadily, the production of production wells increased significantly, and the recovery factor was predicted to reach 54%, an increase of 23 percentage points.

[0045] The present invention also provides a crude oil acquisition device for a fracture-pore type oil reservoir, the device comprising: a reaction unit for injecting air into an injection well, and utilizing a mixture of air and the injected formation crude oil, an oxygen consuming agent, and a catalyst to perform an exothermic oxidation reaction; a closing unit for closing a production well, and forming a hot gas cavity around the injection well based on the heat of the exothermic oxidation reaction; a forming unit for forming microcracks in the matrix reservoir rock of the fracture-pore type oil reservoir based on the hot gas cavity, and expanding the matrix crude oil into the fracture system; a converging unit for converging crude oil to form an oil wall based on the fracture system; and a production unit for opening the production well, continuously injecting air into the injection well, and stably producing the production well.

[0046] Since the content protected by this device is similar to that protected by the above method, we will not introduce it in detail here. Please refer to the discussion section of the above method for details.

[0047] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for developing crude oil in a fracture-pore type reservoir, characterized in that: The method comprises: Injecting air into the injection well, and utilizing the mixture of air, injected formation crude oil, oxygen consuming agent and catalyst to carry out an oxidative exothermic reaction; The production well is shut down, and a hot gas cavity is formed around the injection well due to the heat of the oxidation exothermic reaction; Based on the hot gas cavity, micro-fractures are formed in the matrix reservoir rock of the fracture-pore type oil reservoir, and the matrix crude oil expands into the fracture system; Based on the fracture system, crude oil gathers to form an oil wall; The production wells are opened, air is continuously injected into the injection wells, and the production wells produce stably.

2. The method according to claim 1, characterized in that Inject air into the injection well and use the mixture of air, injected formation crude oil, oxygen consuming agent and catalyst to carry out oxidation exothermic reaction, including: injecting a mixture of formation crude oil, oxygen consuming agent and catalyst into the injection well in sequence; Injecting hot foam fluid into the injection well, and using the hot foam fluid to push the mixture of formation crude oil, oxygen consuming agent and catalyst into the target area of ​​the formation; Air is injected into the injection well, and an exothermic oxidation reaction is carried out using a mixture of air, injected formation crude oil, oxygen consuming agent and catalyst.

3. The method according to claim 1, characterized in that The injection volume of the formation crude oil is (1-1.5)×hm 3 ; where h is the perforation height.

4. The method according to claim 1, wherein The injection amount of the mixture of oxygen consuming agent and catalyst is (0.2~0.5)×hm 3 ; where h is the perforation height.

5. The method according to claim 1, wherein The mass percentage of the catalyst is 1-5%.

6. The method according to claim 2, characterized in that The injection amount of the hot foam liquid is (1-1.5)×hm 3 ; where h is the perforation height.

7. The method according to claim 1, characterized in that The speed of injecting air into the injection well is (1500~2500)×h Nm 3 / d; where h is the perforation height.

8. The method according to claim 1, characterized in that The injection well continuously injects air at a rate of (1000-1500)×h Nm 3 / d.

9. The method according to claim 8, characterized in that The injection well continuously injects air for 30-90 days and the amount of air injected is (75000-150000)×h Nm 3 ; where h is the perforation height.

10. A crude oil development device for a fracture-pore type oil reservoir, characterized in that: The device comprises: A reaction unit is used to inject air into the injection well and utilize the mixture of the air, the injected formation crude oil, the oxygen consuming agent and the catalyst to perform an exothermic oxidation reaction; A shut-in unit for shutting down the production well, forming a hot gas cavity around the injection well based on the heat of the oxidation exothermic reaction; A formation unit for forming micro-fractures in matrix reservoir rocks of fracture-pore type oil reservoirs based on hot gas cavities, and for expanding matrix crude oil into the fracture system; Convergence unit, used for crude oil convergence to form oil wall based on fracture system; The production unit is used to open the production well, continuously inject air into the injection well, and ensure stable production of the production well.

Images