Patent Application
20240117714
This application claims the benefit of priority from Chinese Patent Application No. 202310901418.9, filed on Jul. 21, 2023. The content of the aforementioned application, including any intervening amendments thereto, is incorporated herein by reference in its entirety.
This application relates to oil-gas field development, and more particularly to a method for increasing crude oil production by CO2 storage in an aquifer and dumpflooding.
The massive emission of greenhouse gases represented by CO2 has triggered many environmental and ecological problems. The reduction of CO2 emission has attracted worldwide attention. The researches conducted by European and American countries and Japan have proven that Carbon Capture and Storage (CCS) technology may be one of the effective measures of reducing the CO2 emission. The sites suitable for geological storage of CO2 mainly include abandoned oil-gas reservoirs, deep saltwater aquifers and coal seams with no mining value. Sedimentary basins are widely distributed in the land and continental shelf in China, which have a wide distribution area, and a large sedimentary thickness. Moreover, the saline aquifers suitable for geological storage of CO2 has a large CO2 storage capacity, and thus are highly potential for CO2 storage. However, the CCS projects alone cannot bring direct economic benefits and require mass capital investment. At the same time, the pressure accumulation effect in the process of large-scale CO2 injection will lead to abnormal changes in the pressure of the deep aquifers, which will cause fracture in the overburden layer or fault reactivation, easily resulting in secondary geologic disasters. Therefore, the storage capacity of large-scale industrialized CO2 injection is largely limited, and it fails to ensure the safety of geological storage. Ex-situ pumping from the geological medium is an effective way to regulate the pressure, but it will further increase the operating cost of CCS. In addition, carbon capture, utilization and storage (CCUS) is also a key large-scale CO2 emission reduction technology. The CO2 enhanced oil recovery (EOR) is an effective means to improve the economy of the CCUS technology, but its practical application also faces the following challenges. (1) The CO2 injection will easily result in gas channeling phenomenon, which will seriously affect the sweep efficiency and reduce the oil displacement effect. (2) When the light components of crude oil are extracted from a CO2-crude oil mixture, serious asphaltene precipitation will occur, resulting in blockage of the flow channel. (3) After mixed with crude oil, a large amount of CO2 will be extracted continuously along with the crude oil, and return to the atmosphere, and only a small portion of gas is retained, so that there is still a huge amount of CO2 needed to be removed by geological storage. Therefore, it is worthwhile to pay attention to how to realize efficient and safe CO2 injection in oil-gas basins with complex depositional environments and tectonics, control the influence range of the injection operation, and realize synergistic CO2 storage and increased crude oil production while fully utilizing the underground pore space.
Chinese patent No. 113389533B discloses an integrated method of CO2 capture, reservoir modification and crude oil extraction. In this patent, an imidazole compound, a metal-organic framework (MOF) material and an alcohol are mixed to form a mixed base fluid, which is used to capture CO2 from the industrial gas emission. A cross-linking agent and a thickening agent are added to the mixed base fluid that has captured CO2 to form an alcohol-base fracturing fluid. The alcohol-base fracturing fluid is injected into the reservoir wellhead for fracturing reconstruction of the reservoir, and an acidic gel-breaker plug is injected to release the CO2 to extract the crude oil.
Chinese patent Publication No. 114278257A discloses a device and method for synchronous offshore oilfield exploitation and supercritical CO2 storage. By means of a multilateral well, the simultaneous oil-gas exploitation and CO2 storage in different layers at the same well location is enabled, which not only effectively reduces the CO2 emission from the operation of an offshore production platform, but also reduces the cost of marine CO2 storage.
Chinese patent No. 108131122B discloses a method of improving CO2 storage and crude oil recovery. The pressure safety limit of the target area is determined based on the stability evaluation of caprock and fault in the target area of CO2 oil displacement and storage. A reasonable pressure maintenance level is selected by reservoir numerical simulation. According to reservoir parameters, suitable production parameters and process methods are selected to realize the longitudinal balanced CO2 flooding. According to the non-homogeneity of the reservoirs in the target area and the abundance distribution of the remaining reserve, variable well pattern and spacing and differential reservoir modification are used to realize the planar balanced CO2 flooding. The injection-production flow line is adjusted by optimizing the injection method, injection rate, injection-production regulation methods and foam plugging methods.
Chinese patent Publication No. 115637966A discloses a method for geothermal-driven catalytic reduction CO2 storage and oil recovery. The method combines the liquid nitrogen fracturing with injectant injection, and fully utilizes the thermal energy of the deep geothermal reservoir. The method also introduces a nano-Cu-based catalyst to realize the hydrothermal cracking reaction of crude oil as well as the CO2 thermal reduction reaction, thereby improving the crude oil recovery rate, the CO2 storage capacity, storage stability, and storage efficiency.
In the above-mentioned patent literatures, the crude oil recovery rate, CO2 storage capacity and storage efficiency are improved often by CO2 injection control in oil reservoirs and synergistic oil recovery and CO2 storage. However, it is still difficult to realize large-scale CO2 storage in oil-gas reservoirs. Therefore, how to find a more suitable technology for synergistic CO2 storage and enhanced crude oil production in oil-gas basins to further solve the problems of the existing technical solutions have received extensive attention.
In view of the deficiencies in the prior art, this application provides a method for increasing crude oil production by CO2 storage in an aquifer and dumpflooding. A well is drilled in an aquifer of an oil-gas bearing basin for large-scale CO2 storage, and at the same time, a low-production and low-efficiency well away from the CO2 injection well at the oil-bearing stratum is selected as the artesian injection well. The groundwater with a continuously-rising pressure is controlled and guided to flow from the aquifer into the oil-bearing stratum, thereby enabling the dump flooding for oil displacement in the oil-bearing stratum. This application can not only achieve the large-scale safe CO2 storage in the deep aquifer, but also enhance the crude oil recovery from the oil-bearing stratum.
Technical solutions of this application are described as follows.
This application provides a method of increasing crude oil production by CO2 storage in an aquifer and dump flooding, comprising:
(1) selecting an aquifer within a regional unit of an oil-bearing basin; drilling at least one CO2 injection well in a structural high part of the aquifer, wherein a perforation position of each of the at least one CO2 injection well is located at a middle-lower part of the aquifer; and within the regional unit of the oil-bearing basin, selecting a deep aquifer with a wide distribution, a burial depth of greater than 800 m, a stable regional cap-rock or an aquiclude, few faults or strong fault sealing, a formation water salinity of greater than 3 g/L, and good compatibility with an oil-bearing stratum;
(2) drilling at least two production wells for depletion development in the regional unit of the oil-bearing basin, wherein at least one of the at least two production wells is drilled to encounter both an oil-bearing stratum and the aquifer; and a perforation position of each of the at least two production wells is located at a middle-upper part of the oil-bearing stratum;
(3) from the at least two production wells, selecting one with a distance of 3 km or more from the at least one CO2 injection well, and a daily oil production of less than 2 t/d or insufficient fluid supply for normal production as an artesian injection well; and perforating the artesian injection well at the middle-lower part of the aquifer, so as to communicate the aquifer with the oil-bearing stratum through a wellbore of the artesian injection well;
(4) deploying a flow-pressure detecting-controlling device in the artesian injection well, wherein the flow-pressure detecting-controlling device is located near a junction of the oil-bearing stratum and an interbedded stratum in the wellbore, and is configured to monitor and control a dump flooding rate and a flooding pressure, which can be realized by adopting a variety of structures of the prior art; and deploying sequentially a first packer and a second packer in the artesian injection well, wherein the first packer is located near a top boundary of the aquifer for isolating and sealing a well section above the aquifer; and the second sealer is located near a bottom boundary of the oil-bearing stratum for isolating and sealing a well section below the oil-bearing stratum; and
(5) continuously injecting CO2 into a geological body of the aquifer for storage through the at least one CO2 injection well; based on an reservoir pressure accumulation effect within the aquifer during the storage of CO2, under the action of a pressure difference between the aquifer and the oil-bearing stratum, allowing formation water in the aquifer to flow into the wellbore of the artesian injection well and the flow-pressure detecting-controlling device; adjusting a flow rate and the flooding pressure of the flow-pressure detecting-controlling device, to make the formation water within the aquifer to flow into the oil-bearing stratum at a preset flow rate to displace crude oil to an adjacent production well for extraction.
Compared to the prior art, this application has the following beneficial effects.
CO2 is injected into the deep aquifer for large-scale storage, and is used to drive the formation water in the deep aquifer to flow into the oil-bearing stratum for oil displacement. On one hand, it can effectively alleviate the problems of reservoir pressure accumulation and salt precipitation in the large-scale CO2 injection into the deep aquifer, improve the injectability and safety of CO2, and significantly increase the dissolved and captured amount of CO2, thereby effectively improving the storage efficiency of CO2. On the other hand, the dump flooding is enabled by controlling the pressure difference between the aquifer and the oil-bearing stratum, which can effectively replenish the energy deficit of the oil-bearing stratum, improve the development effect of the oil-bearing stratum regional unit, and realize the maximized utilization of oil-gas resources and underground reservoir space. Therefore, this application can not only alleviate the shortage of strategic resources, but also produce obvious economic and social benefits.
In the FIGURE: 1—aquifer; 2—oil-bearing stratum; 3—regional cap-rock; 4—interbedded stratum; 5—CO2 injection well; 6—first production well; 7—second production well; 8—third production well; 9—flow-pressure detecting and controlling device; 10—first packer; and 11—second packer.
(1) Within the regional unit of the oil-bearing basin, the aquifer 1 with a wide distribution, a burial depth of greater than 800 m, a stable regional cap-rock, few faults or strong fault sealing, a formation water salinity of greater than 3 g/L, and good compatibility with an oil-bearing stratum is selected. One CO2 injection well 5 is drilled in a structural high part of the aquifer 1.
In this embodiment, there is the stable regional cap-rock 3 above the aquifer 1, and there is an interbedded stratum 4 between the aquifer 1 and the oil-bearing stratum 2. The first injection position of the CO2 injection well is located at a middle-lower part of the aquifer 1.
(2) Three production wells are drilled in the regional unit of the oil-bearing stratum 2 in the oil-bearing basin, namely a first production well 6, a second production well 7, and a third production well 8, for depletion development.
In this embodiment, the first production well 6, the second production well 7, and the third production well 8 are drilled to encounter both the aquifer 1 and the oil-bearing stratum 2. The perforation positions of the first production well 6, the second production well 7, and the third production well 8 are located at the middle-upper part of the oil-bearing stratum 2. The well spacing between the first production well 6, the second production well 7, and the third production well 8 ranges between 200 m and 500 m.
(3) From the production wells, one production well with the distance of 3 km or more from the CO2 injection well 5, and the daily oil production of less than 2 t/d or insufficient fluid supply for normal production is selected as an artesian injection well. The artesian injection well is perforated at the middle-lower part of the aquifer 1, so as to communicate the aquifer 1 with the oil-bearing stratum 2 through the wellbore of the artesian injection well.
In this embodiment, the first production well 6, which has insufficient fluid supply for normal production, is preferred as the artesian injection well. The first production well 6 is perforated at the middle-lower part of the aquifer 1, while perforating the oil-bearing stratum 2 and the aquifer 1 above the oil-bearing stratum 2.
(4) The flow-pressure detecting-controlling device 9 is deployed in the first production well 6. In this embodiment, the flow-pressure detecting-controlling device 9 is located at the junction of the oil-bearing stratum 2 and the interbedded strata 4 in the wellbore, so as to monitor and control the dumpflooding rate and the flooding pressure, which can be realized by adopting a variety of structures of the existing technology. The first packer 10 and the second packer 11 are deployed in the first production well 6.
In this embodiment, the flow-pressure detecting-control device 9 is provided with a pressure sensor and a flow meter together. The pressure sensor can monitor the pressure of the oil-bearing stratum in the wellbore of the first production well 6. The flow meter can monitor and control the dump flooding rate, and adjust the flooding pressure of the oil-bearing stratum in the wellbore of the first production well 6.
In this embodiment, the first packer 10 is located at a top boundary of the aquifer 1 for isolating and sealing a well section above the aquifer 1. The second packer 11 is located at a bottom boundary of the oil-bearing stratum 2 for isolating and sealing a well section below the oil-bearing stratum 2.
(5) CO2 fluid is continuously injected into the geological body of the aquifer 1 for large-scale storage through the CO2 injection well 5. At the same time, based on the reservoir pressure accumulation effect within the aquifer 1 during the large-scale storage of CO2, and under the action of the progressively increasing pressure difference between the aquifer 1 and the oil-bearing stratum 2, the formation water within the aquifer 1 flows into the wellbore of the first production well 6 and the flow-pressure detecting-controlling device 9. The flow rate and flooding pressure of the flow-pressure detecting-controlling device 9 are adjusted to control the formation water within the aquifer 1 to inject into the oil-bearing stratum 2 at a reasonable flow rate, thereby displacing crude oil to the neighboring second production well 7 and third production well 8. Then the crude oil is extracted from the second production well 7 and third production well 8.
By injecting CO2 into the deep aquifer for large-scale storage and controlling and guiding the formation water in the deep aquifer to flow into the oil-bearing stratum, the disclosure realizes synergistic oil displacement by CO2 geological storage in the deep aquifer and by dump flooding in the oil-bearing stratum. On one hand, the disclosure improves the injectability and safety of the large-scale storage of CO2 and effectively improves the storage efficiency of CO2. On the other hand, the disclosure can effectively replenish the energy of the oil-bearing stratum, improve the development effect of crude oil in the oil-bearing stratum, maximize the utilization of oil-gas resources and underground reservoir space, and obtain the double benefits of economy and environmental protection, which has great potential for application in the geographical areas where the oil-gas production industry develops faster and water is scarce, such as Xinjiang and Inner Mongolia.
| Number | Date | Country | Kind |
|---|---|---|---|
| 202310901418.9 | Jul 2023 | CN | national |
