Horizontal well air heat injection mixed-phase oil extraction method and device suitable for buried hill oil reservoir

Abstract

The invention discloses a horizontal well air injection hot mixed-phase oil extraction method suitable for buried hill oil reservoirs, which solves the problem that the conventional gas injection huff and puff development is small in gas injection scale and difficult to greatly supplement energy, fully utilizes the gas suction capacity of a horizontal well, injects flue gas generated by reaction of air and crude oil at the gas injection amount far beyond the conventional injection scale, and improves the oil extraction efficiency. And by utilizing the development advantage of the fractured buried hill fracture system, the generated flue gas rapidly overcovers the top of the oil layer to form a gas cap, stable gas cap driving is realized, remaining oil at the top of the oil layer can be effectively utilized, and the development effect of the fractured buried hill oil reservoir is effectively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of oil production, and in particular to a method and device for producing oil by injecting hot mixed phase air into a horizontal well suitable for a buried hill oil reservoir. Background Art

[0002] Fractured buried-hill reservoirs are characterized by large structural amplitudes, thick reservoirs, and a high degree of fracture development. They exhibit dual-medium characteristics, with complex reservoir spaces. Low-permeability matrix rocks are typically the primary reservoir for oil and gas, while highly permeable fracture systems serve as the primary flow pathways. Compared to conventional reservoirs, fractured reservoirs have more complex flow characteristics and are more challenging to develop.

[0003] Therefore, how to reduce the difficulty of oil production in fractured reservoirs has become a technical problem that needs to be solved urgently. Summary of the Invention

[0004] The present invention aims to provide a horizontal well air injection hot miscible oil production method suitable for buried hill oil reservoirs to solve the above technical problems.

[0005] To achieve the above object, the present invention provides a method for producing oil by injecting hot miscible air into a horizontal well suitable for a buried hill oil reservoir, comprising:

[0006] The air thermal mixing is started by sequentially injecting formation crude oil, catalytic oxygen consuming agent, hot foam liquid and air into the horizontal well;

[0007] Continuously inject large volumes of air into horizontal wells to form a gas cap at the top of the oil layer;

[0008] Stop injecting air into the horizontal well and shut down the well, and the crude oil in the fracture system migrates by gravity to form an oil wall.

[0009] Control the fluid production rate of horizontal wells and use horizontal wells for oil production.

[0010] The present invention also provides a horizontal well air injection hot miscible phase oil production device suitable for buried hill oil reservoirs, comprising:

[0011] A start-up unit is used to start the air hot mixed phase by using the formation crude oil, catalytic oxygen consuming agent, hot foam liquid and air injected into the formation in sequence;

[0012] The injection unit is used to continuously inject large volumes of air into the horizontal well to form a gas cap at the top of the oil layer. The injection of air into the horizontal well can be stopped by shutting down the injection unit and then the well is shut down. The crude oil in the fracture system migrates by gravity to form an oil wall.

[0013] The oil production unit is used to control the liquid production rate of the horizontal well and use the horizontal well to produce oil.

[0014] Technical effects and advantages of the present invention:

[0015] (1) This method breaks the problem of small-scale gas injection and difficulty in significantly replenishing energy in conventional gas injection development. It fully utilizes the air suction capacity of horizontal wells and injects flue gas generated by the reaction of air and crude oil at a gas injection volume far exceeding the conventional injection scale. By taking advantage of the development of fractured buried-hill fracture systems, the generated flue gas quickly overlaps the top of the oil layer to form a gas cap, achieving stable gas cap drive. It can also effectively mobilize the remaining oil at the top of the oil layer, effectively improving the development effect of fractured buried-hill reservoirs.

[0016] (2) This method consumes air to efficiently generate miscible gas inside the reservoir, realizes air injection thermal miscibility, reduces oil-gas interfacial tension, and at the same time, the miscible gas enters the matrix pores, dissolves the matrix crude oil and expands due to temperature increase, realizes the expansion self-drive of the matrix crude oil, and overcomes the difficulty of utilizing the matrix crude oil in fractured reservoirs.

[0017] (3) This method has a simple injection-production relationship, low cost investment, and simple operation. It fully utilizes the existing horizontal production wells and does not require large-scale thermal completion. The injection medium is air, which is simple and easy to obtain and does not require medium costs. It also overcomes the problems of corrosion, transportation, and complex injection processes in conventional gas injection development.

[0018] 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

[0019] Figure 1 The flow chart of the horizontal well air injection hot miscible oil production method suitable for buried hill oil reservoirs. DETAILED DESCRIPTION

[0020] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the 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.

[0021] 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.

[0022] Horizontal wells are a key method for developing fractured buried hills, characterized by high liquid production capacity. However, horizontal wells produce oil quickly but decline rapidly, making effective energy replenishment in the later stages of development difficult. This presents significant technical challenges in increasing single-well production and recovery rates. Gas injection is currently a key method for improving oil recovery, with the injected gas typically including natural gas, CO2, and nitrogen. However, the high cost and transportation of the injected gas, the technical difficulties of field operations, and significant crossflow issues have limited the large-scale application of conventional gas injection development.

[0023] Air injection thermal miscibility technology refers to the technology of injecting catalytic oxygen-consuming agents and air into the formation through injection wells to preheat and start the oil layer, forming a medium-high temperature thermal oxidation state of the formation crude oil and air. The medium-high temperature flue gas generated by thermal oxidation and liquid crude oil achieve phase change thermal miscibility, eliminate interfacial tension, overcome capillary force effects, effectively mobilize the crude oil in the matrix pores, and significantly improve the recovery rate.

[0024] Air injection hot miscible phase technology continuously injects air into the reservoir to generate high-temperature thermal oxidation. The resulting miscible gas has its miscible phase pressure significantly reduced under high-temperature conditions, achieving thermal miscibility with the liquid crude oil and achieving an oil recovery efficiency exceeding 90%. Furthermore, the injected air medium in hot miscible phase development can be sourced from a wide range of sources, eliminating the need for media costs. This avoids the high media costs associated with conventional gas injection development, which hinders large-scale application. Furthermore, the technology offers simple on-site operation, low operating costs, high development efficiency, and a wide range of applications.

[0025] Air injection hot miscible flooding technology has successfully conducted field trials, achieving significant technological breakthroughs. Horizontal well gas injection and huff-and-puff is a key method for improving oil recovery. Conventional gas injection and huff-and-puff methods, however, suffer from limited gas injection capacity, short well shut-in periods, significant gas crossflow issues after well production begins, and a short effective huff-and-puff period. Therefore, the present invention applies air hot miscible flooding technology and horizontal well huff-and-puff development techniques to the development of fractured buried-hill reservoirs, significantly increasing their production and recovery.

[0026] The following combination Figure 1 The invention discloses a method for horizontal well air injection hot miscible oil recovery applicable to buried hill oil reservoirs, which specifically includes:

[0027] 1. Initiate air hot mixing by sequentially injecting formation crude oil, catalytic oxygen consuming agent, hot foam liquid and air into the formation.

[0028] Specifically: (1) Targeted selection of fractured buried hill reservoirs suitable for air injection development, where the oil layer has dual medium characteristics, natural fractures are widely developed, the oil layer structural amplitude is greater than 100m, the formation temperature is greater than 50℃, and horizontal wells are arranged in the middle and lower parts of the oil layer.

[0029] (2) Air hot mixed phase start-up: Inject formation crude oil, catalytic oxygen consuming agent, hot foam liquid and air into the formation in sequence through horizontal wells. In which, inject formation crude oil (0.2~0.5)×lm into the horizontal well. 3 ; Inject catalyst (wt1~5%) + oxygen consuming agent plug into the horizontal well, injection temperature 0~40℃, injection volume (0.1~0.5)×lm 3 , where l is the length of the horizontal well; the amount of hot foam fluid injected is (0.2~0.5)×lm 3 , used to clean the wellbore to ensure that there is no residual oil hanging on the wall; then inject air at a high speed, the injection speed is (0.04~0.1)×l×10 4 Nm 3 / d, utilizing the formation temperature (>50℃) to generate oxidation heat to complete efficient oxygen consumption startup.

[0030] The catalyst is metal oxides of nickel and cobalt, and the oxygen-consuming agent is a mixture of potassium permanganate and sodium nitrate.

[0031] 2. Continuously inject large volumes of air into the horizontal well to form a gas cap at the top of the oil layer.

[0032] Specifically, continuous high-volume and high-speed air injection is used to establish a stable thermal oxidation state between the reservoir crude oil and air to achieve thermal miscibility, and the matrix crude oil expands and self-drives into the fracture system; then, the flue gas generated by the reaction between the crude oil and air overlaps the top of the oil layer along the fracture system to form a stable gas cap.

[0033] Among them, the injection speed is (20~50)×10 4 Nm 3 / d, continuous air injection for 50 to 100 days, cumulative air injection of 1000 to 2000×10 4 Nm 3 .

[0034] 3. Stop injecting air into the horizontal well and shut down the well. The crude oil in the fracture system migrates by gravity to form an oil wall.

[0035] Among them, the well soaking time is 30-50 days.

[0036] 4. Control the fluid production rate of horizontal wells and use horizontal wells for oil production.

[0037] Specifically: control the fluid production rate of horizontal wells, maintain a reasonable bottom hole flow pressure, achieve stable gas cap drive, and suppress the rapid coning of bottom water.

[0038] The present invention protects an oil production method for fractured buried-hill oil reservoirs by injecting hot mixed phases of air. The method comprises four main development stages: air hot mixed phase startup, large-scale air injection to create an artificial gas cap, shutting down wells to create an oil wall, and stable production of horizontal wells. Taking full advantage of the large structural amplitude of the buried-hill oil reservoir, horizontal wells are arranged in the middle and lower parts of the reservoir. By establishing an air hot mixed phase state, the oil layer temperature is increased, the oil-gas interface tension is reduced, and the matrix crude oil expands and drives itself, thereby effectively utilizing the matrix crude oil; through large-scale air injection, the gas overburden is fully utilized to establish an artificial gas cap of flue gas, effectively utilizing the remaining oil in the cracks at the top of the oil layer; large-scale air injection can significantly increase the formation pressure, replenish the formation energy, and inhibit the coning of bottom water; the well is shut down for 30-50 days, and the crude oil in the fracture system migrates by gravity to form an oil wall; the liquid production rate of the horizontal well is controlled during the well opening and production phase to achieve stable gas cap drive, thereby significantly increasing the production and recovery rate of the fractured buried-hill oil reservoir.

[0039] In order to better understand the present solution, examples are provided below.

[0040] Example

[0041] This example establishes a double permeability numerical simulation theoretical model based on the actual situation of the Liaohe Oilfield oil reservoir block. The average burial depth of the oil reservoir is 2800m, the buried hill structure amplitude is 500m, the effective oil layer thickness is 130m, the formation temperature is 95℃, the matrix permeability is 2mD, the fracture permeability is 330mD, the original formation pressure is about 28MPa, the bottom water is developed, and the oil-water interface is 480m from the top of the reservoir. The block deploys vertical wells at the top of the oil layer for depletion development, with a fixed liquid production of 100m 3 / d, depletion development to an average formation pressure of 18 MPa and a recovery rate of 30%.

[0042] The following are the methods for hot miscible air injection huff and puff oil recovery:

[0043] 1. Shut in the vertical production wells and arrange horizontal wells 100m above the oil-water interface with a length of 500m;

[0044] 2. Inject 200m3 of formation crude oil into the horizontal wells 3 , catalyst + oxygen consuming agent 100m 3 , hot foam agent 200m 3 , air (injection rate is 20-50×10 4Nm 3 / d), to achieve hot miscible startup;

[0045] 3. Continuously inject large volume of air at a speed of 25×10 4 Nm 3 / d, gas injection for 40 days, cumulative gas injection 1000×10 4 Nm 3 , forming a gas cap;

[0046] 4. Stop air injection and keep the well incubated for 30 days to allow a stable oil wall to form within the fracture system;

[0047] 5. The production wells were put into production, and the recovery rate was predicted to reach 51%, an increase of 21 percentage points.

[0048] The present invention also provides a horizontal well air injection hot miscible phase oil production device suitable for buried hill oil reservoirs, comprising:

[0049] A start-up unit is used to start the air hot mixed phase by using the formation crude oil, catalytic oxygen consuming agent, hot foam liquid and air injected into the formation in sequence;

[0050] The injection unit is used to continuously inject large volumes of air into the horizontal well to form a gas cap at the top of the oil layer. The injection of air into the horizontal well can be stopped by shutting down the injection unit and then the well is shut down. The crude oil in the fracture system migrates by gravity to form an oil wall.

[0051] The oil production unit is used to control the liquid production rate of the horizontal well and use the horizontal well to produce oil.

[0052] 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.

[0053] 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 producing oil by injecting hot miscible air into a horizontal well of a buried hill oil reservoir, characterized in that: include: The air thermal mixing is started by sequentially injecting formation crude oil, catalytic oxygen consuming agent, hot foam liquid and air into the horizontal well; Continuously inject large volumes of air into horizontal wells to form a gas cap at the top of the oil layer; Stop injecting air into the horizontal well and shut down the well, and the crude oil in the fracture system migrates by gravity to form an oil wall. Control the fluid production rate of horizontal wells and use horizontal wells for oil production.

2. The method according to claim 1, characterized in that Before starting the air thermal miscibility by sequentially injecting formation crude oil, catalytic oxygen consuming agent, hot foam liquid and air into the horizontal well, the method further includes: screening the buried hill reservoir; The oil layer structure amplitude of the buried hill oil reservoir is greater than 100m, the formation temperature is greater than 50°C, and the horizontal wells are arranged in the middle and lower part of the oil layer.

3. The method according to claim 1, characterized in that The injection volume of the formation crude oil is (0.2-0.5)×lm 3 The injection amount of the catalytic oxygen consuming agent is (0.1-0.5)×lm 3 The injection amount of the hot foam liquid is (0.2~0.5)×lm 3 ; Where l is the length of the horizontal well.

4. The method according to claim 1, wherein The mass percentage of the catalyst in the catalytic oxygen-consuming agent is 1 to 5%.

5. The method according to claim 1, wherein The injection temperature of the catalytic oxygen-consuming agent is 0-40°C.

6. The method according to claim 1, characterized in that The injection speed of the large displacement air is (20-50)×10 4 Nm 3 / d, injection time is 50 to 100 days.

7. The method according to claim 1, characterized in that Continuously injecting secondary air into horizontal wells to form a gas cap on top of the oil layer, including: By continuously injecting large volumes of air into horizontal wells, the matrix crude oil is self-propelled into the fracture system through expansion; The flue gas generated by the reaction of the matrix crude oil with air overlaps the top of the oil layer along the fracture system to form a stable gas cap.

8. The method according to claim 1, characterized in that The time for stewing the well is 30-50 days.

9. Applicable to horizontal well air injection hot miscible oil production equipment in buried hill oil reservoirs, characterized by: include: A start-up unit is used to start the air hot mixed phase by using the formation crude oil, catalytic oxygen consuming agent, hot foam liquid and air injected into the formation in sequence; The injection unit is used to continuously inject large volumes of air into the horizontal well to form a gas cap at the top of the oil layer. The injection of air into the horizontal well can be stopped by shutting down the injection unit and then the well is shut down. The crude oil in the fracture system migrates by gravity to form an oil wall. The oil production unit is used to control the liquid production rate of the horizontal well and use the horizontal well to produce oil.

10. The device according to claim 9, characterized in that The injection volume of the formation crude oil is (0.2-0.5)×lm 3 The injection amount of the catalytic oxygen consuming agent is (0.1-0.5)×lm 3 The injection amount of the hot foam liquid is (0.2~0.5)×lm 3 ; Where l is the length of the horizontal well.

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