Horizontal well separation pressure drive mining method

Abstract

The invention relates to the technical field of oil exploitation methods, in particular to a horizontal well separation pressure drive exploitation method which comprises the following steps: (1) preferably selecting an oil reservoir suitable for a target; (2) selecting a horizontal well with insufficient stratum energy after production for a period of time, and injecting water into the horizontal well; (3) injecting water into the tail end of the horizontal section of the horizontal well; (4) after water injection of the tail end is completed, water injection of the horizontal section is continued, and operation is circulated until water injection of the whole horizontal section is completed through the continuous oil pipe; during water injection, water injection parameters of the horizontal well are adjusted in time according to reservoir characteristics, and injection-production balance is formed. According to the horizontal well level-separated pressure-drive mining method, the influence of parameters such as oil reservoir physical properties and reservoir rock brittleness on water injection huff and puff development is considered, the injection pressure, the injection amount and the soaking time are optimized and researched while the injection mode is improved, and the method has the advantages that the development efficiency is improved, and the development cost is reduced. The method has important guiding significance for improving the recovery ratio through horizontal well water injection huff and puff.

Description

Technical Field

[0001] The invention relates to the technical field of oil production methods, and is a horizontal well step-by-step pressure-driven production method. Background Art

[0002] Water injection huff and puff is a development method for injecting water and producing oil in the same well. It means that when the formation energy decreases and the production is very low, water is injected into the production well to restore the formation pressure, and then the well is shut down for a certain period of time. Water is injected to replace the crude oil by imbibition, and then the well is opened for production to produce crude oil. It is suitable for small oil reservoirs with low natural energy and no energy supplement, and need to improve the recovery rate. Due to the complex artificial fractures formed after multi-stage fracturing of horizontal wells, the effective seepage channels for reservoir crude oil to flow into the bottom of the well are increased, and the area of ​​the seepage area is expanded. Injecting gas or water in the adjacent wells of the production well is very likely to cause gas channeling or water flooding, reducing the oil production capacity of the oil well. Implementing water injection huff and puff for fractured horizontal wells can fully rely on their own complex fracture network, expand the contact area between the horizontal well and the reservoir, and replace the crude oil through the imbibition of the injected water. After multiple water injection wells and imbibition oil production, the displacement multiple is increased, thereby improving the crude oil recovery rate. However, the current horizontal well water injection and huff-and-puff mainly adopts a general water injection method. Faced with strong reservoir heterogeneity, especially oil reservoirs with large differences in fracture development between horizontal well sections, it is easy to cause over-injection in high-permeability sections and under-injection in low-permeability sections, seriously affecting the water injection and huff-and-puff development effect of horizontal wells. Summary of the invention

[0003] The present invention provides a horizontal well step-by-step pressure-driven production method, which overcomes the shortcomings of the above-mentioned prior art and can effectively solve the problem of overinjection of high permeability sections and underinjection of low permeability sections caused by different opening degrees of perforation sections in horizontal wells in low permeability and extra-low permeability oil reservoirs during horizontal well water injection.

[0004] The technical solution of the present invention is achieved by the following measures: A horizontal well step-by-step pressure-driven mining method is carried out according to the following steps: Step (1), selecting a suitable target reservoir; Step (2), selecting a horizontal well whose formation energy is insufficient after a period of production, and injecting water into it for huff-and-puff production to improve the single well recovery rate; Step (3), lowering a coiled tubing with a differential pressure packer at the bottom into the horizontal well, and injecting water into the end of the horizontal section of the horizontal well by utilizing the isolation effect of the differential pressure packer; Step (4), after the end water injection is completed, the coiled tubing is dragged to the front end of the horizontal well, and water injection into the horizontal section is continued, and the operation is circulated until the entire horizontal section is injected with water by the coiled tubing. After the horizontal section is injected with water, the well is shut down, and the horizontal well is switched to continuous production, and production continues until the end; In the steps (3) to (4), during water injection, the horizontal well water injection parameters are timely adjusted according to the reservoir characteristics to form an injection-production balance.

[0005] The following are further optimizations and / or improvements to the above technical solutions: Furthermore, in the above step (1), a rough screening of suitable reservoirs is performed, and the selected oil layer thickness is >10m, the oil layer porosity is >0.2, the horizontal permeability is >5mD, the oil saturation is >0.40, there is no continuous mud interlayer in the oil layer, the formation crude oil viscosity is less than 10000mPa.s, the rock brittleness index is less than 40%, and the plane double-wing fractures are mainly formed during fracturing, and it is difficult to form a complex fracture network in the oil reservoir.

[0006] Furthermore, in the above step (2), according to different reservoir conditions and the production and development conditions of different horizontal wells, horizontal wells with low single well production and insufficient formation energy are selected.

[0007] Furthermore, in the above steps (3) to (4), the injection parameters of the horizontal well must be adjusted during water injection, the injection pressure is less than the extension pressure, the injection volume is 0.3 to 0.5 times the pore volume, and attention is paid to maintaining pressure balance and controlling the overall production-injection ratio.

[0008] The original crack can be reopened only when the injection pressure is greater than the closing pressure, and it can be avoided when it is less than the extension pressure (FPP) to prevent the crack from forming again.

[0009] Furthermore, in the above step (4), considering the fracture initiation threshold pressure and the drop in bottom hole pressure during the well shut-in period, it is better to comprehensively determine the shut-in time to be 25 to 30 days.

[0010] The horizontal well inter-stage pressure-driven production method described in the present invention not only takes into account the influence of parameters such as reservoir physical properties and reservoir rock brittleness on water injection throughput development, but also optimizes the injection pressure, injection volume and well soaking time while improving the injection method. It has important guiding significance for improving the recovery rate of horizontal well water injection throughput. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Attached Figure 1 Schematic diagram of water injection into the bottom of the horizontal section of the water injection pipe.

[0012] Attached Figure 2 Schematic diagram of water injection into the middle of the horizontal section through the water injection pipe.

[0013] Attached Figure 3 Schematic diagram of the relationship between water injection multiple and recovery factor.

[0014] Attached Figure 4 This is a schematic diagram of the relationship between well soaking time and recovery rate.

[0015] The codes in the attached drawings are: 1 is a differential pressure packer, and 2 is a well killing sliding sleeve. DETAILED DESCRIPTION

[0016] The present invention is not limited by the following embodiments, and specific implementation methods can be determined based on the technical solution of the present invention and actual conditions.

[0017] In the present invention, unless otherwise specified, the tools used are all existing well-known and commonly used tools, such as differential pressure packers.

[0018] The present invention provides a horizontal well inter-stage pressure-driven production method, which 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 soaking time while improving the injection method, which has important guiding significance for improving the recovery rate of horizontal well water injection and huff-and-puff. Compared with the traditional general water injection and huff-and-puff, this method fully considers the influence of parameters such as reservoir heterogeneity and reservoir rock brittleness on horizontal well water injection and huff-and-puff development, is more in line with the actual situation on site, has a more obvious production increase effect, has a lower investment cost than surfactants and repeated fracturing, and has better economic benefits.

[0019] The present invention will be further described below in conjunction with embodiments: Example 1: A horizontal well step-by-step pressure-driven mining method is carried out according to the following steps: Step (1), selecting a suitable target reservoir; Step (2), selecting a horizontal well whose formation energy is insufficient after a period of production, and injecting water into it for huff-and-puff production to improve the single well recovery rate; Step (3), lowering a coiled tubing with a differential pressure packer at the bottom into the horizontal well, and injecting water into the end of the horizontal section of the horizontal well by utilizing the isolation effect of the differential pressure packer; Step (4), after the end water injection is completed, the coiled tubing is dragged to the front end of the horizontal well, and water injection into the horizontal section is continued, and the operation is circulated until the entire horizontal section is injected with water by the coiled tubing. After the horizontal section is injected with water, the well is shut down, and the horizontal well is switched to continuous production, and production continues until the end; In the steps (3) to (4), during water injection, the horizontal well water injection parameters are timely adjusted according to the reservoir characteristics to form an injection-production balance.

[0020] In step (3), the coiled tubing has a differential pressure packer at the bottom, and water can be injected between the differential pressure packers. Figure 1 .

[0021] In step (4), after the coiled tubing is lowered into the horizontal well, water injection is started from the end of the horizontal well section. After the water injection at the end is completed, the coiled tubing is dragged to the front end to continue water injection into the horizontal section. The cycle operation is repeated until the entire horizontal section is fully injected. Figure 2 .

[0022] Example 2: As an optimization of the above example, in step (1), a rough screening of suitable oil reservoirs is performed, and the selected oil layer thickness is >10m, the oil layer porosity is >0.2, the horizontal permeability is >5mD, the oil saturation is >0.40, there is no continuous mud interlayer in the oil layer, the formation crude oil viscosity is less than 10000mPa.s, the rock brittleness index is less than 40%, and the oil reservoir in which planar double-wing fractures are mainly formed during fracturing and it is difficult to form a complex fracture network.

[0023] Embodiment 3: As an optimization of the above embodiment, in step (2), according to different reservoir conditions and the production and development conditions of different horizontal wells, horizontal wells with low single well production and insufficient formation energy are selected.

[0024] Example 4: As an optimization of the above example, in step (3) to step (4), the injection parameters of the horizontal well must be adjusted during water injection, the injection pressure is less than the extension pressure, the injection volume is 0.3 to 0.5 times the pore volume, and attention is paid to maintaining pressure balance and controlling the overall production-injection ratio.

[0025] During water injection, the relationship between water injection multiple and recovery factor is shown in Figure 3 ,Depend on Figure 3 From the numerical simulation results, it can be seen that the injection water volume should be designed to be 0.3 to 0.5 times.

[0026] Example 5: As an optimization of the above example, in step (4), taking into account the fracture initiation threshold pressure and the drop in bottom hole pressure during the well shut-in period, a shut-in period of 25 to 30 days is comprehensively determined to be a better effect.

[0027] The relationship between soaking time and recovery rate is shown in Figure 4 , considering the fracture initiation threshold pressure and the drop in bottom hole pressure during the shut-in period, Figure 4 It can be seen that the comprehensive determination of the well-sealing time should be between 25 and 30 days for better results.

[0028] Implementation Cases This implementation case provides a horizontal well step-by-step pressure-driven mining method, which includes the following specific steps: (1) A rough screening of the reservoir was conducted. The selected continuous oil layer had a thickness of 20 m, a porosity of 0.30, a horizontal permeability of 24 mD, an oil saturation of 0.72, no continuous mudstone or shale interlayers, a formation crude oil viscosity of 5000 mPa.s, and a brittleness index of 22.1%.

[0029] A horizontal well that has been producing for more than one year was selected in the reservoir. Currently, the water content has reached more than 90%, the liquid volume has dropped by 50%, and both the oil production and liquid production are at a relatively low level.

[0030] A coiled tubing with a differential pressure packer was run into the horizontal well, and water was injected from the bottom. After the bottom water injection was completed, the coiled tubing was continuously dragged to continue injecting water into the horizontal section until the entire horizontal section was injected with water. At the same time, the water injection parameters were adjusted according to the characteristics of each reservoir section to maintain the overall water injection rate of 240m 3 / d, water injection pressure 9MPa, wheel water injection volume 6000m 3 .

[0031] After the water injection is completed, the well is shut down for 22 days. After the well is shut down, it is put into production for cyclic throughput production. The overall production-injection ratio is controlled at around 1.2 until the end.

[0032] Compared with conventional horizontal well water injection, the peak oil production increased from 25t / d to 46t / d, the peak oil production rate increased by 77%, the ultimate recovery factor increased by 7.9%, and the oil-gas ratio increased by 0.02.

[0033] It can be seen from this implementation case that the horizontal well inter-stage pressure-driven production method described in the present invention can significantly improve the recovery rate.

[0034] The above technical features constitute the embodiments of the present invention, which have strong adaptability and implementation effect. Non-essential technical features can be added or reduced according to actual needs to meet the requirements of different situations.

Claims

1. A horizontal well step-by-step pressure-driven mining method, characterized in that Follow these steps: Step (1), selecting a suitable target reservoir; Step (2), selecting a horizontal well whose formation energy is insufficient after a period of production, and injecting water into it for huff-and-puff production to improve the single well recovery rate; Step (3), lowering a coiled tubing with a differential pressure packer at the bottom into the horizontal well, and injecting water into the end of the horizontal section of the horizontal well by utilizing the isolation effect of the differential pressure packer; Step (4), after the end water injection is completed, the coiled tubing is dragged to the front end of the horizontal well, and water injection into the horizontal section is continued, and the operation is circulated until the entire horizontal section is injected with water by the coiled tubing. After the horizontal section is injected with water, the well is shut down, and the horizontal well is switched to continuous production, and production continues until the end; In the steps (3) to (4), during water injection, the horizontal well water injection parameters are timely adjusted according to the reservoir characteristics to form an injection-production balance.

2. The horizontal well step-by-step pressure-driven mining method according to claim 1 is characterized in that In step (1), a rough screening of suitable reservoirs is performed, and the selected oil layer thickness is >10m, the oil layer porosity is >0.2, the horizontal permeability is >5mD, the oil saturation is >0.40, there is no continuous mud interlayer in the oil layer, the formation crude oil viscosity is less than 10000mPa.s, the rock brittleness index is less than 40%, and the plane double-wing fractures are mainly formed during fracturing, and it is difficult to form a complex fracture network.

3. The horizontal well step-by-step pressure-driven mining method according to claim 1 or 2, characterized in that In step (2), according to different reservoir conditions and the production and development status of different horizontal wells, horizontal wells with low single well production and insufficient formation energy are selected.

4. The horizontal well step-by-step pressure-driven mining method according to claim 1 or 2, characterized in that In step (3) to step (4), the injection parameters of the horizontal well must be adjusted during water injection. The injection pressure is less than the extension pressure, and the injection volume is 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.

5. The horizontal well step-by-step pressure-driven mining method according to claim 3 is characterized in that In step (3) to step (4), the injection parameters of the horizontal well must be adjusted during water injection. The injection pressure is less than the extension pressure, and the injection volume is 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.

6. The horizontal well step-by-step pressure-driven mining method according to claim 1 or 2, characterized in that In step (4), taking into account the fracture initiation threshold pressure and the drop in bottom hole pressure during the shut-in period, the shut-in time is comprehensively determined to be 25 to 30 days.

7. The horizontal well step-by-step pressure-driven mining method according to claim 3 is characterized in that In step (4), taking into account the fracture initiation threshold pressure and the drop in bottom hole pressure during the shut-in period, the shut-in time is comprehensively determined to be 25 to 30 days.

8. The horizontal well step-by-step pressure-driven mining method according to claim 4 is characterized in that In step (4), taking into account the fracture initiation threshold pressure and the drop in bottom hole pressure during the shut-in period, the shut-in time is comprehensively determined to be 25 to 30 days.

9. The horizontal well step-by-step pressure-driven mining method according to claim 5, characterized in that In step (4), taking into account the fracture initiation threshold pressure and the drop in bottom hole pressure during the shut-in period, the shut-in time is comprehensively determined to be 25 to 30 days.

Images