A method for overall reconstruction of an old oilfield block

Abstract

The present application relates to the technical field of overall repeated reconstruction of old oilfield blocks, and specifically provides an overall reconstruction method for old oilfield blocks, which stops water injection of all water injection wells in a target oilfield according to the dynamic change rules of the seepage field, pressure field and stress field of the fractured well of the target oilfield under long-term water injection conditions, and changes the water injection wells into oil production wells; and the three types of oil wells in the old oilfield are reconstructed one by one according to their characteristics, so that the water injection wells are effectively changed into oil production wells, and the production of the changed oil production wells is improved, and the development effect is enhanced. In the detection of the fracture direction of the target oilfield and the configuration relationship of the sand body, well pattern and fracture network, the natural fracture distribution, fracturing fracture morphology representation and modeling method are adopted to depict the natural fractures and fracturing fractures, and provide quantitative basis for repeated fracturing optimization.

Description

Technical Field

[0001] This invention relates to the field of overall repeated renovation technology for old oilfield blocks, specifically a method for overall renovation of old oilfield blocks. Background Technology

[0002] Ultra-low permeability crude oil production accounts for nearly one-third of the total crude oil production and is an important support for the continuous and stable production of oil fields. At present, the development of ultra-low permeability reservoirs by water injection faces many development challenges, such as difficulty in establishing an effective matrix displacement pressure system, multi-directional fracture water flooding, a large proportion of low-yield and inefficient wells, low oil production rate, large production decline, small lateral water injection range in fractures, and enrichment of residual oil, resulting in poor development effects.

[0003] Therefore, it is necessary to explore integrated treatment technologies for old oilfields to improve the recovery rate of ultra-low permeability reservoirs, based on the development characteristics of old reservoirs and oil reservoirs. Summary of the Invention

[0004] To address the problems of low overall production and poor development effect in existing water-injected ultra-low permeability oilfields, this invention provides a method for the overall transformation of old oilfield blocks. This method can improve the overall production of old oilfields and enhance development effectiveness.

[0005] This invention is achieved through the following technical solution:

[0006] A method for the overall renovation of an old oilfield block includes the following steps:

[0007] S1. Select the target oil field and detect the fracture direction and the configuration relationship of sand body, well network and fracture network in the target oil field to obtain the dynamic change law of seepage field, pressure field and stress field of the fractured well in the target oil field under long-term water injection conditions.

[0008] S2, by observing the dynamic changes in the seepage field, pressure field, and stress field of the fractured wells in the target oilfield under long-term water injection conditions, stops water injection in all water injection wells in the target oilfield and converts the water injection wells into oil production wells;

[0009] S3 involves modifying all production wells within the target oilfield.

[0010] Preferably, in S1, the detection of fracture direction and the configuration relationship of sand body, well network and fracture network in the target oilfield is carried out by using natural fracture distribution, fracturing fracture morphology characterization and modeling methods to characterize natural fractures and fracturing fractures.

[0011] Preferably, in S3, all production wells in the target oilfield include low-yield horizontal wells, directional wells in old oilfields, and wells that have been modified.

[0012] For low-production horizontal wells in the oilfield, the old horizontal well large-displacement volume repressurization process is used for overall treatment. The external sealing technology of fiber filtration and multi-stage particle size plugging agent filling is used to prevent external leakage between the pipes in the old horizontal wells.

[0013] For directional wells in old oilfields, a comprehensive approach is adopted, including pre-fracturing energy replenishment, mixed water fracturing, temporary plugging of old fractures, and multi-well synchronous fracturing.

[0014] For oil wells in old oilfields that have been repeatedly modified, when production declines, water injection and huff-and-puff technology can be used to replenish formation energy and restore production capacity.

[0015] Furthermore, for horizontal wells with low production in oilfields, the replenishment fluid volume needs to be optimized in the large-volume repressurization process of old horizontal wells so that the local formation pressure can be restored to the original formation pressure.

[0016] Furthermore, the specific methods for treating low-yield horizontal wells in oilfields using the large-volume, high-pressure repressurization process for older horizontal wells are as follows:

[0017] Based on the definition of formation compressibility coefficient, the relationship between cumulative water injection volume and pressure change is obtained;

[0018] Based on the formation pressure values ​​measured in oil wells that need to be repeatedly modified, the amount of water injection required to raise the formation pressure to a certain level is calculated, and this amount of water injection is the amount of replenishing fluid.

[0019] The amount of sand required to support the fracture was simulated, and then the amount of fluid required to carry the sand into the fracture was calculated based on the amount of sand.

[0020] After injecting the required amount of fluid into a single well, shut in the well and increase the pressure. Observe the pressure drop at the wellhead. If the pressure at the wellhead is higher than the limit and remains stable, stop injecting water; otherwise, continue injecting water to replenish energy.

[0021] Using the model, the cumulative fluid production under different fracturing stages was simulated, and the optimal number of fracturing stages was determined based on the simulation results.

[0022] The fracture half-length was optimized by calculating the relationship between the fracture half-length and the well spacing based on the well spacing and the available geological reserves between wells, in accordance with the requirement of full fracture coverage.

[0023] Optimize the fracturing displacement and calculate the net pressure inside the fracture when the natural fractures in the reservoir undergo tensile fracturing; draw a chart of net pressure inside the fracture, reservoir thickness, and fracturing displacement, and determine the displacement of volumetric fracturing based on the chart comparison results.

[0024] Furthermore, the specific methods for replenishing energy before fracturing in the overall treatment of directional well groups in old oilfields are as follows:

[0025] Before fracturing, directional wells inject oil-displacing fracturing fluid at a rate of 1 cubic meter per minute. After fracturing, the well is left to simmer for a period of time to increase local formation energy.

[0026] Furthermore, in the overall treatment of directional well groups in old oilfields, when large fractures are connected between wells within the group, polymer microspheres, polymer gels, and 70-140 mesh sand are first used to seal the distal end of the water-bearing channel and the matrix; then, high-strength plugging agents are used to seal the fractures before fracturing is carried out; during the fracturing process, slug-type sand is added, and under the condition of a certain amount of sand, multiple slugs are arranged to add sand.

[0027] Furthermore, for oil wells in old oilfields that have been repeatedly modified, when using water injection and huff-and-puff technology to supplement formation energy, it is necessary to optimize the timing of the huff-and-puff. According to the changes in bottom hole pressure during the oil well production period, the recovery rate is highest when the formation pressure is 75-80% of the original formation pressure. That is, water injection and huff-and-puff tests should be started when the formation pressure drops to 75-80% of the original formation pressure.

[0028] Furthermore, for oil wells in old oilfields that have been repeatedly modified, when using water injection and huff-and-puff technology to replenish formation energy, the throughput needs to be optimized. At the end of the water injection period, the pressure maintenance level needs to reach 100%, and the designed throughput should be increased or decreased based on the pressure maintenance level value.

[0029] Furthermore, for oil wells in old oilfields that have been repeatedly modified, when using water injection and huff-and-puff technology to replenish formation energy, it is necessary to optimize the well shut-in time. Combined with the production rate of the wells in the field, oil production should begin when the wellhead pressure is stable and no longer declining.

[0030] Compared with the prior art, the present invention has the following beneficial technical effects:

[0031] This invention provides a method for the overall transformation of an old oilfield block. By analyzing the dynamic changes in the seepage field, pressure field, and stress field of the fractured wells in the target oilfield under long-term water injection conditions, all water injection wells in the target oilfield are stopped and converted into oil production wells. Furthermore, the method is modified one by one according to the characteristics of the three types of oil wells existing in the old oilfield, so that the water injection wells are effectively converted into oil production wells, thereby increasing the production of the converted oil production wells and enhancing the development effect.

[0032] Furthermore, in detecting the fracture direction and the configuration relationship between sand bodies, well networks, and fracture networks in the target oilfield, natural fracture distribution, fracturing fracture morphology characterization, and modeling methods are used to characterize natural fractures and fracturing fractures, providing a quantitative basis for repeated fracturing optimization.

[0033] Furthermore, by integrating a rational formation pressure system, well network, well type and volume modification, and an integrated development and design method for energy replenishment, the formation pressure can be quickly restored to 100-120% of its normal level; the contact area between fractures and reservoirs can be increased, while connecting the original water storage area with the remaining oil area; the shut-in time can be optimized based on the wellhead pressure drop, so that the elastic driving energy and oil-water can be further balanced on the plane, and production can be further improved through percolation replacement.

[0034] Furthermore, by integrating technologies such as comprehensive energy replenishment, volumetric modification, and synchronous fracturing, the production of single wells is significantly increased. The large-displacement volumetric repressurization process of horizontal wells is used to improve construction efficiency and carry out overall modification of horizontal wells in the oilfield.

[0035] Furthermore, the use of fiber filtration and multi-stage particle size plugging agent to fill the external sealing pipe technology prevents leakage between the pipes in old horizontal wells, and effective pressure distribution is achieved through plugging.

[0036] Furthermore, with the aim of increasing the overall volume of the well group and supplementing energy, technologies such as pre-fracturing water injection, mixed fracturing, temporary plugging of old fractures, and multi-well synchronization are integrated to improve the overall fracturing effect of directional well groups in old areas.

[0037] Furthermore, numerical simulations are used to optimize well shut-in time, injection timing, and injection parameters to ensure maximum permeation effect. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of the overall transformation method for converting old oilfield water injection wells into oil production well blocks in this invention. Detailed Implementation

[0039] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0040] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0041] The present invention will now be described in further detail with reference to the accompanying drawings:

[0042] See Figure 1 In one embodiment of the present invention, a method for the overall transformation of an old oilfield block is provided, which can increase the overall production of the old oilfield and enhance the development effect.

[0043] Specifically, the method for the overall transformation of the old oilfield's water injection wells into oil production well blocks includes the following steps:

[0044] S1. Select the target oil field, study the fracture direction of the target oil field and the configuration relationship of sand body, well network and fracture network, detect the fracture direction of the target oil field and the configuration relationship of sand body, well network and fracture network, and obtain the dynamic change law of seepage field, pressure field and stress field of the fractured well of the target oil field under long-term water injection conditions.

[0045] Specifically, in detecting the fracture direction and the configuration relationship between sand bodies, well networks, and fracture networks in the target oilfield, natural fracture distribution, fracturing fracture morphology characterization, and modeling methods are used to characterize natural fractures and fracturing fractures.

[0046] S2, by observing the dynamic changes in the seepage field, pressure field, and stress field of the fractured wells in the target oilfield under long-term water injection conditions, stops water injection in all water injection wells in the target oilfield and converts the water injection wells into oil production wells;

[0047] S3 involves modifying all production wells within the target oilfield.

[0048] Specifically, this includes all production wells in the target oilfield, including low-yield horizontal wells, directional wells in old oilfields, and wells that have already been modified.

[0049] For low-production horizontal wells in the oilfield, the old horizontal well large-displacement volume repressurization process is used for overall treatment. The external sealing technology of fiber filtration and multi-stage particle size plugging agent filling is used to prevent external leakage between the pipes in the old horizontal wells.

[0050] For directional wells in old oilfields, a comprehensive approach is adopted, including pre-fracturing energy replenishment, mixed water fracturing, temporary plugging of old fractures, and multi-well synchronous fracturing.

[0051] For oil wells in old oilfields that have been repeatedly modified, when production declines, water injection and huff-and-puff technology can be used to replenish formation energy and restore production capacity.

[0052] For horizontal wells with low production in oilfields, the replenishment fluid volume needs to be optimized in the large-volume repressurization process of old horizontal wells so that the local formation pressure can be restored to the original formation pressure.

[0053] The specific methods for treating low-yield horizontal wells in oilfields using the large-volume, high-pressure repressurization process for older horizontal wells are as follows:

[0054] The replenishment fluid volume needs to be optimized so that the local formation pressure can be restored to the original formation pressure. First, based on the definition of the formation compressibility coefficient, the relationship between the cumulative injection volume and pressure change needs to be obtained. Then, based on the formation pressure values ​​measured in the wells that need to be repeatedly drilled, the injection volume required to raise the formation pressure to a certain level is calculated. This injection volume is the replenishment fluid volume.

[0055] Using reservoir engineering analysis methods and numerical simulation methods, the amount of sand required to support the fractures is simulated, and then the amount of fluid required to carry sand into the fractures per well is calculated based on the amount of sand.

[0056] After injecting 1000 cubic meters of fluid at a time, shut in the well and allow it to expand for 12 hours. Observe the pressure drop at the wellhead. If the pressure at the wellhead is higher than 2 MPa and remains stable, stop the injection. Otherwise, continue injecting water to replenish energy.

[0057] StimPlan software is needed to simulate and calculate the model to establish parameters such as horizontal section length, reservoir thickness, porosity, formation pressure, effective permeability, fracture half-fracture length, and fracture conductivity. The model will then be used to simulate the cumulative fluid production over 90 days for different numbers of fracturing stages, and the optimal number of fracturing stages will be determined based on the simulation results.

[0058] The fracture half-length needs to be optimized first. Specifically, the well spacing and the available geological reserves between wells need to be considered, and the relationship between the fracture half-length and the well spacing needs to be calculated according to the requirement of full fracture coverage.

[0059] The fracturing displacement needs to be optimized. Specifically, based on the fracturing criteria proposed by Warpinski and Teufel, the required net pressure within the fracture should be calculated when tensile fracturing occurs in the natural fractures of the reservoir; a graph showing the net pressure within the fracture versus reservoir thickness and fracturing displacement should be drawn, and the displacement of volumetric fracturing should be determined based on the graph comparison results.

[0060] The specific methods for replenishing energy before fracturing in the overall treatment of directional well groups in old oilfields are as follows:

[0061] Before fracturing, approximately 200 cubic meters of oil displacement fracturing fluid are injected into the directional well at a flow rate of 1 cubic meter per minute. After fracturing, the well is left to simmer for about 14 days to increase local formation energy.

[0062] For cases where large fractures are interconnected between wells within a well group, the distal end of the water-reaching channel and the matrix are first sealed using polymeric microspheres, polymeric gel, and 70-140 mesh sand. Then, a high-strength plugging agent is used to seal the fracture before fracturing is performed. During fracturing, slug-type proppant is added, and as many slugs as possible are deployed given a fixed amount of proppant.

[0063] For oil wells in old oilfields that have been repeatedly modified, when using water injection and huff-and-puff technology to supplement formation energy, it is necessary to optimize the timing of the huff-and-puff. According to the changes in bottom hole pressure during the oil well production period, the recovery rate is the highest when the formation pressure is 75-80% of the original formation pressure. That is, water injection and huff-and-puff tests should be started when the formation pressure drops to 75-80% of the original formation pressure.

[0064] For oil wells in old oilfields that have been repeatedly modified, when using water injection and huff-and-puff technology to replenish formation energy, the throughput needs to be optimized. At the end of the water injection period, the pressure maintenance level needs to reach 100%, and the designed throughput should be increased or decreased according to the pressure maintenance level value.

[0065] For oil wells in old oilfields that have been repeatedly modified, when using water injection and huff-and-puff technology to replenish formation energy, it is necessary to optimize the well shut-in time. Combining the production rate of the wells in the field, oil production should begin when the wellhead pressure is stable and no longer decreasing.

[0066] Example

[0067] This embodiment provides a method for the overall transformation of an old oilfield block, including the following steps:

[0068] Step 1) Collect dynamic data of oil well production in old oilfields, current production status map, sand body map, analyze fracture direction and well network and fracture network configuration relationship, and use natural fracture distribution, fracturing fracture morphology characterization and modeling methods to obtain the dynamic change law of seepage field, pressure field and stress field under long-term water injection conditions of fracturing wells in the oilfield.

[0069] Step 2) Stop water injection in all water wells in the target oil field and convert water injection wells into production wells, that is, all wells in the oil field are production wells and no longer carry out water drive;

[0070] Step 3) For horizontal wells with low production in the oilfield, the large-volume re-pressure process of old horizontal wells is used for overall repeated fracturing. First, according to the definition of formation compressibility coefficient, the relationship between cumulative water injection volume and pressure change is obtained. Based on the formation pressure value measured in the wells to be repeatedly modified, the water injection volume required to raise the formation pressure to a certain level is calculated. This water injection volume is the replenishing fluid volume.

[0071] Step 4) When replenishing formation energy before fracturing an old horizontal well, observe the wellhead pressure drop. If the wellhead pressure is higher than 2MPa and remains stable, stop the injection; otherwise, continue water injection to replenish energy.

[0072] Step 5) Optimize the fracture half-length, number of stimulation sections, displacement, and fluid injection volume of the old horizontal well to be repeatedly fracturing, and then carry out on-site construction according to the optimized parameters;

[0073] Step 6) For the directional well to be modified, inject about 200 cubic meters of oil displacement fracturing fluid at a flow rate of 1 cubic meter / minute before fracturing, and shut the well for about 14 days after fracturing.

[0074] Step 7) During repeated directional well stimulation, if large fractures are found to be interconnected between wells within the well group, first use polymeric microspheres, polymeric gel, and 70-140 mesh sand to seal the distal end of the water-bearing channel and the matrix; then use a high-strength plugging agent to seal the fractures before proceeding with fracturing. During fracturing, use slug-type proppant injection, and deploy as many slugs as possible while maintaining a fixed amount of proppant.

[0075] Step 8) If the production of oil wells that have been repeatedly modified in an old oilfield drops significantly again, water injection and spitting-out measures should be implemented. First, optimize the timing, throughput, and well shut-in time of the spitting-out, and then carry out the spitting-out.

[0076] In summary, this invention provides a method for the overall transformation of an old oilfield block. By analyzing the dynamic changes in the seepage field, pressure field, and stress field of the fractured wells in the target oilfield under long-term water injection conditions, all water injection wells in the target oilfield are stopped and converted into production wells. Furthermore, based on the characteristics of the three types of oil wells existing in the old oilfield, the method is modified one by one, effectively converting the water injection wells into production wells, thereby increasing the production of the converted production wells and enhancing the development effect.

[0077] The parts of the above embodiments that are not specifically familiar are all common knowledge and common technology in this field, and will not be described in detail here.

[0078] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A method for the overall transformation of an old oilfield block, characterized in that, Includes the following steps: S1. Select the target oil field and detect the fracture direction and the configuration relationship of sand body, well network and fracture network in the target oil field to obtain the dynamic change law of seepage field, pressure field and stress field of the fractured well in the target oil field under long-term water injection conditions. S2, by observing the dynamic changes in the seepage field, pressure field, and stress field of the fractured wells in the target oilfield under long-term water injection conditions, stops water injection in all water injection wells in the target oilfield and converts the water injection wells into oil production wells; S3 involves modifying all production wells within the target oilfield; All production wells in the target oilfield, including low-yield horizontal wells, directional wells in old oilfields, and wells that have been modified; For low-production horizontal wells in the oilfield, the old horizontal well large-displacement volume repressurization process is used for overall treatment. The external sealing technology of fiber filtration and multi-stage particle size plugging agent filling is used to prevent external leakage between the pipes in the old horizontal wells. For directional wells in old oilfields, a comprehensive approach is adopted, including pre-fracturing energy replenishment, mixed water fracturing, temporary plugging of old fractures, and multi-well synchronous fracturing. For oil wells in old oilfields that have been repeatedly modified, when production declines, water injection and huff-and-puff technology can be used to replenish formation energy and restore production capacity. For horizontal wells with low production in oilfields, the amount of replenishing fluid needs to be optimized in the large-volume repressurization process of old horizontal wells so that the local formation pressure can be restored to the original formation pressure. The specific methods for treating low-yield horizontal wells in oilfields using the large-volume, high-pressure repressurization process for older horizontal wells are as follows: Based on the definition of formation compressibility coefficient, the relationship between cumulative water injection volume and pressure change is obtained; Based on the formation pressure values ​​measured in oil wells that need to be repeatedly modified, the amount of water injection required to raise the formation pressure to a certain level is calculated, and this amount of water injection is the amount of replenishing fluid. The amount of sand required to support the fracture was simulated, and then the amount of fluid required to carry the sand into the fracture was calculated based on the amount of sand. After injecting the required amount of fluid into a single well, shut in the well and increase the pressure. Observe the pressure drop at the wellhead. If the pressure at the wellhead is higher than the limit and remains stable, stop injecting water; otherwise, continue injecting water to replenish energy. Using the model, the cumulative fluid production under different fracturing stages was simulated, and the optimal number of fracturing stages was determined based on the simulation results. The fracture half-length was optimized by calculating the relationship between the fracture half-length and the well spacing based on the well spacing and the available geological reserves between wells, in accordance with the requirement of full fracture coverage. Optimize the fracturing displacement and calculate the net pressure inside the fracture when the natural fractures in the reservoir undergo tensile fracturing; draw a chart of net pressure inside the fracture, reservoir thickness, and fracturing displacement, and determine the displacement of volumetric fracturing based on the chart comparison results.

2. The method for overall renovation of an old oilfield block according to claim 1, characterized in that, In S1, the detection of fracture direction and the configuration relationship of sand body, well network and fracture network in the target oilfield is carried out by using natural fracture distribution, fracturing fracture morphology characterization and modeling methods to characterize natural fractures and fracturing fractures.

3. The method for overall renovation of an old oilfield block according to claim 1, characterized in that, The specific methods for replenishing energy before fracturing in the overall treatment of directional well groups in old oilfields are as follows: Before fracturing, directional wells inject oil-displacing fracturing fluid at a rate of 1 cubic meter per minute. After fracturing, the well is left to simmer for a period of time to increase local formation energy.

4. The method for overall renovation of an old oilfield block according to claim 1, characterized in that, In the overall treatment of directional well groups in old oilfields, when large fractures are connected between wells within the group, polymer microspheres, polymer gels, and 70-140 mesh sand are first used to seal the distal end of the water-bearing channel and the matrix; then, high-strength plugging agents are used to seal the fractures before fracturing is carried out; during the fracturing process, slug-type sand is added, and with a certain amount of sand added, multiple slugs are arranged for sand addition.

5. The method for overall renovation of an old oilfield block according to claim 1, characterized in that, For oil wells in old oilfields that have been repeatedly modified, when using water injection and huff-and-puff technology to supplement formation energy, it is necessary to optimize the timing of the huff-and-puff. According to the changes in bottom hole pressure during the oil well production period, the recovery rate is the highest when the formation pressure is 75-80% of the original formation pressure. That is, when the formation pressure drops to 75-80% of the original formation pressure, the water injection and huff-and-puff test should be started.

6. The method for overall renovation of an old oilfield block according to claim 1, characterized in that, For oil wells in old oilfields that have been repeatedly modified, when using water injection and huff-and-puff technology to replenish formation energy, it is necessary to optimize the throughput. At the end of the water injection period, the pressure maintenance level needs to reach 100%, and the designed throughput should be increased or decreased according to the pressure maintenance level value.

7. The method for overall renovation of an old oilfield block according to claim 1, characterized in that, For oil wells in old oilfields that have been repeatedly modified, when using water injection and huff-and-puff technology to replenish formation energy, it is necessary to optimize the well shut-in time. Combining the production rate of the wells in the field, oil production should begin when the wellhead pressure is stable and no longer decreasing.

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