Horizontal well staged pressure drive recovery method

Abstract

The present application relates to the technical field of oil exploitation method, and is a horizontal well graded pressure drive exploitation method, which comprises the following steps: (1) selecting an oil reservoir suitable for the target; (2) selecting a horizontal well with insufficient formation energy after a period of production, and performing water injection on the horizontal well; (3) performing water injection on the end of the horizontal section of the horizontal well; (4) after the water injection on the end is completed, continuing to perform water injection on the horizontal section, and performing cyclic operation until the coiled tubing completes water injection on the entire horizontal section; when water injection is performed, the water injection parameters of the horizontal well are adjusted in a timely manner according to the reservoir characteristics to form injection-production balance. The horizontal well graded pressure drive exploitation method has important guiding significance for improving the recovery rate of the horizontal well water injection and throughput, and not only considers the influence of parameters such as reservoir physical properties and reservoir rock brittleness on water injection and throughput development, but also optimizes the research on injection pressure, injection volume and soaking time while improving the injection mode.

Description

Technical Field

[0001] This invention relates to the field of oil extraction methods, specifically a horizontal well staged pressure drive extraction method. Background Technology

[0002] Water injection huff and puff is a development method that involves injecting water and producing oil in the same well. When formation energy declines and production is very low, water is injected into the production well to restore formation pressure. After a certain period of shut-in, the injected water replaces the crude oil through percolation, and then the well is reopened for production. This method is suitable for small reservoirs with low natural energy and no energy replenishment, where enhanced oil recovery is needed. Because the complex artificial fractures formed after multi-stage fracturing in horizontal wells increase the effective percolation channels for crude oil to flow into the bottom of the well, expanding the percolation area, injecting gas or water into adjacent wells can easily cause gas channeling or water flooding, reducing the well's production capacity. Water injection huff and puff in fractured horizontal wells fully utilizes the complex fracture network to expand the contact area between the horizontal well and the reservoir. The crude oil is replaced by the percolation of injected water. Through multiple water injections and well shut-in cycles, the displacement ratio is increased, thereby improving the crude oil recovery rate. However, the current horizontal well water injection and churn mainly adopts a general water injection method. When facing reservoirs with strong heterogeneity, especially oil reservoirs with large differences in the degree of fracture development between horizontal well sections, it is easy to cause over-injection in high-permeability sections and under-injection in low-permeability sections, which seriously affects the water injection and churn development effect of horizontal wells. Summary of the Invention

[0003] This invention provides a horizontal well staged pressure drive production method that overcomes the shortcomings of the prior art. It can effectively address the problem of over-injection in high-permeability sections and under-injection in low-permeability sections caused by different degrees of opening of the perforation section in horizontal wells in low-permeability and ultra-low-permeability reservoirs during previous horizontal well water injection and churn processes.

[0004] The technical solution of this invention is achieved through the following measures: a horizontal well staged pressure-driven extraction method, comprising the following steps:

[0005] Step (1): Select a suitable target reservoir;

[0006] Step (2): Select horizontal wells with insufficient formation energy after a period of production, and perform water injection and huff-and-puff production to improve the single-well recovery rate;

[0007] Step (3): Run a continuous tubing with a differential pressure packer at the bottom end into the horizontal well and use the sealing effect of the differential pressure packer to inject water into the end of the horizontal section of the horizontal well.

[0008] Step (4): After the water injection at the end is completed, drag the coiled tubing to the front end of the horizontal well and continue to inject water into the horizontal section. Repeat the operation until the coiled tubing has injected water into the entire horizontal section. After the water injection into the horizontal section is completed, shut the well and switch the horizontal well to continuous production. Continue production until the end.

[0009] In steps (3) to (4), the injection parameters of the horizontal well are adjusted in a timely manner according to the reservoir characteristics during water injection to form an injection-production balance.

[0010] The following are further optimizations and / or improvements to the above-mentioned technical solution:

[0011] Furthermore, in step (1) above, a suitable reservoir is selected for rough screening. The selected reservoir has a thickness >10m, a porosity >0.2, a horizontal permeability >5mD, an oil saturation >0.40, no continuous mudstone interlayers in the reservoir, a crude oil viscosity of less than 10000mPa.s, a rock brittleness index of less than 40%, and a reservoir that is mainly composed of planar double-wing fractures and is difficult to form a complex fracture network during fracturing.

[0012] Furthermore, in step (2) above, based on different reservoir conditions and the production and development of different horizontal wells, horizontal wells with low single-well production and insufficient formation energy are selected.

[0013] Furthermore, in steps (3) to (4) above, the water injection parameters of the horizontal well must be adjusted during water injection, the injection pressure is less than the extension pressure, the water injection volume is 0.3 to 0.5 times the pore volume, and at the same time, attention should be paid to maintaining pressure balance and controlling the overall production-injection ratio.

[0014] Only when the water injection pressure is greater than the closing pressure can the original crack be reopened; if it is less than the extension pressure (FPP), the crack will not be re-created.

[0015] Furthermore, in step (4) above, considering the fracture initiation threshold pressure and the drop in bottom hole pressure during well shut-in, a well shut-in time of 25 to 30 days is determined to be more effective.

[0016] The horizontal well staged pressure drive production method described in this invention not only considers the influence of parameters such as reservoir physical properties and reservoir rock brittleness on water injection and huff-and-puff development, but also optimizes the injection pressure, injection volume and well shut-in time while improving the injection method. It has important guiding significance for improving the recovery rate of horizontal well water injection and huff-and-puff. Attached Figure Description

[0017] Appendix Figure 1 A schematic diagram showing water being injected into the bottom of the horizontal section of the water injection pipe.

[0018] Appendix Figure 2 This is a schematic diagram of water being injected into the middle of the horizontal section of the water injection pipe.

[0019] Appendix Figure 3 This is a schematic diagram showing the relationship between the water injection ratio and the recovery rate.

[0020] Appendix Figure 4 This is a schematic diagram showing the relationship between well shut-in time and recovery rate.

[0021] The codes in the attached diagram are as follows: 1 is a differential pressure packer, and 2 is a well-killing sliding sleeve. Detailed Implementation

[0022] The present invention is not limited to the following embodiments, and the specific implementation can be determined according to the technical solution of the present invention and the actual situation.

[0023] Unless otherwise specified, all tools used in this invention are existing, well-known, and commonly used tools, such as differential pressure packers.

[0024] This invention provides a horizontal well staged hydraulic fracturing method that not only considers the impact of reservoir properties and reservoir rock brittleness on water injection development, but also optimizes injection pressure, injection volume, and well shut-in time while improving the injection method. This method has significant guiding significance for improving oil recovery through horizontal well water injection development. Compared with traditional, general water injection development, this method fully considers the impact of reservoir heterogeneity and reservoir rock brittleness on horizontal well water injection development, making it more suitable for actual field conditions and resulting in a more significant production increase. It also offers lower investment costs and better economic benefits compared to surfactants and repeated fracturing.

[0025] The present invention will be further described below with reference to embodiments:

[0026] Example 1: Horizontal well staged pressure drive production method, carried out according to the following steps:

[0027] Step (1): Select a suitable target reservoir;

[0028] Step (2): Select horizontal wells with insufficient formation energy after a period of production, and perform water injection and huff-and-puff production to improve the single-well recovery rate;

[0029] Step (3): Run a continuous tubing with a differential pressure packer at the bottom end into the horizontal well and use the sealing effect of the differential pressure packer to inject water into the end of the horizontal section of the horizontal well.

[0030] Step (4): After the water injection at the end is completed, drag the coiled tubing to the front end of the horizontal well and continue to inject water into the horizontal section. Repeat the operation until the coiled tubing has injected water into the entire horizontal section. After the water injection into the horizontal section is completed, shut the well and switch the horizontal well to continuous production. Continue production until the end.

[0031] In steps (3) to (4), the injection parameters of the horizontal well are adjusted in a timely manner according to the reservoir characteristics during water injection to form an injection-production balance.

[0032] In step (3), the coiled tubing has a differential pressure packer at the bottom, and water can be injected between the differential pressure packers. For tubing strings where water cannot be injected externally, see attached... Figure 1 .

[0033] In step (4), after the coiled tubing is lowered into the horizontal well, water injection begins from the end of the horizontal section. After water injection at the end is completed, the coiled tubing is dragged towards the front end to continue water injection into the horizontal section. This cycle is repeated until the entire horizontal section is water-injected, as shown in the attached diagram. Figure 2 .

[0034] Example 2: As an optimization of the above example, in step (1), a suitable reservoir is screened. The selected reservoir has a thickness >10m, a porosity >0.2, a horizontal permeability >5mD, an oil saturation >0.40, no continuous mudstone interlayers in the reservoir, a crude oil viscosity of less than 10000mPa.s, a rock brittleness index of less than 40%, and a reservoir that is mainly formed by planar double-wing fractures during fracturing and is difficult to form a complex fracture network.

[0035] Example 3: As an optimization of the above example, in step (2), based on different reservoir conditions and the production and development of different horizontal wells, a horizontal well with low single-well production and insufficient formation energy is selected.

[0036] Example 4: As an optimization of the above example, in steps (3) to (4), the water injection parameters of the horizontal well must be adjusted during water injection, the injection pressure is less than the extension pressure, the water injection volume is 0.3 to 0.5 times the pore volume, and at the same time, attention should be paid to maintaining pressure balance and controlling the overall production-injection ratio.

[0037] During water injection, the relationship between the water injection ratio and the recovery rate is shown in the figure. Figure 3 ,Depend on Figure 3 Numerical simulation results show that the designed injection volume should be 0.3 to 0.5 times.

[0038] Example 5: As an optimization of the above example, in step (4), considering the fracture initiation threshold pressure and the decrease in bottom hole pressure during well shut-in, it is better to determine the well shut-in time to be 25 to 30 days.

[0039] The relationship between well shut-in time and recovery rate is shown in the figure. Figure 4 Considering the fracture initiation threshold pressure and the drop in bottom hole pressure during well shut-in, by Figure 4 It can be concluded that a well-sealing time of 25 to 30 days is more effective.

[0040] Implementation Cases

[0041] This implementation case provides a horizontal well staged pressure-driven production method, which includes the following specific steps:

[0042] (1) The reservoir was roughly screened. The selected continuous oil layer was 20m thick, with a porosity of 0.30, a horizontal permeability of 24mD, an oil saturation of 0.72, and no continuous mudstone or shale interlayers. The crude oil viscosity was 5000mPa.s and the brittleness index was 22.1%.

[0043] Within this oil reservoir, a horizontal well that has been producing for more than a year was selected. Currently, the water cut is over 90%, the fluid volume has decreased by 50%, and both oil and fluid production are at a low level.

[0044] A coiled tubing system with a differential pressure packer was run into the horizontal well. Water injection began from the bottom end. After bottom water injection was completed, the coiled tubing was continuously dragged to continue water injection into the horizontal section until the entire horizontal section was water-injected. At the same time, the water injection parameters were adjusted according to the reservoir characteristics of each section to maintain an overall water injection rate of 240m. 3 / d, water injection pressure 9MPa, water injection volume 6000m³ 3 .

[0045] After water injection is completed, the well is kept closed for 22 days. After the well is closed, it is put into production and circulated production is carried out. The overall production-injection ratio is controlled at around 1.2 until the end.

[0046] Compared with conventional horizontal well water injection huff and puff, the peak oil production increased from 25t / d to 46t / d, the peak oil production rate increased by 77%, the final recovery rate increased by 7.9%, and the oil-gas ratio increased by 0.02.

[0047] As can be seen from this implementation case, the horizontal well staged pressure drive mining method of the present invention can significantly improve the recovery rate.

[0048] The above technical features constitute the embodiments of the present invention, which have strong adaptability and implementation effect. Unnecessary technical features can be added or removed according to actual needs to meet the needs of different situations.

Claims

1. A horizontal well staged pressure-driven extraction method, characterized in that... Follow these steps: Step (1): Select a suitable target reservoir; Step (2): Select horizontal wells with insufficient formation energy after a period of production, and perform water injection and huff-and-puff production to improve the single-well recovery rate; Step (3): Run a coiled tubing with a differential pressure packer at the bottom end into the horizontal well and inject water into the end of the horizontal section of the horizontal well using the sealing effect of the differential pressure packer; Step (4): After the water injection at the end is completed, drag the coiled tubing to the front end of the horizontal well and continue to inject water into the horizontal section. Repeat the operation until the coiled tubing has injected water into the entire horizontal section. After the water injection into the horizontal section is completed, shut the well and switch the horizontal well to continuous production. Continue production until the end. In steps (3) to (4), the injection parameters of the horizontal well are adjusted in a timely manner according to the reservoir characteristics during water injection to form an injection-production balance. In step (1), a suitable reservoir is selected for rough screening. The selected reservoir has a thickness >10m, a porosity >0.2, a horizontal permeability >5mD, an oil saturation >0.40, no continuous mudstone interlayers, a crude oil viscosity of less than 10000mPa.s, a rock brittleness index of less than 40%, and a reservoir that is mainly composed of planar double-wing fractures and is difficult to form a complex fracture network during fracturing. In step (2), based on different reservoir conditions and the production and development of different horizontal wells, horizontal wells with low single-well production and insufficient formation energy are selected. In steps (3) to (4), the injection parameters of the horizontal well must be adjusted during water injection. The injection pressure should be less than the extension pressure, and the injection volume should be 0.3 to 0.5 times the pore volume. At the same time, attention should be paid to maintaining pressure balance and controlling the overall production-injection ratio. In step (4), taking into account the fracture initiation threshold pressure and the drop in bottom hole pressure during well shut-in, the well shut-in time is determined to be 25 to 30 days.

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