A method for integrating tight reservoir reconstruction with injection, flooding and production

Abstract

The present invention belongs to the technical field of oil and gas field development, and specifically relates to a method for integrated reservoir transformation of tight reservoirs by "pressure-injection-drive-production". The main steps of the method include: conducting pressure-driven reservoir simulation by measuring the tectonic stress field and predicting the development of natural fractures, and then optimizing the pressure-driven injection-production well network, designing the pressure-driven process, and utilizing the fracture network formed after fracturing. The artificial fractures increase the displacement area and the swept volume, significantly improve the reservoir recovery rate, and make it possible to efficiently develop low-permeability reservoirs by water drive. The process is simple. After fracturing, pressure-driven water injection is implemented to communicate the natural fractures of the formation, expand the transformation volume, and the fluid seeps into the formation to replenish the formation energy; at the same time, the fluid contacts the reservoir matrix, making full use of the imbibition oil recovery mechanism to improve the crude oil recovery rate. In addition, the use of pressure-driven water injection can reduce the use of fracturing materials (fracture fluid, proppant) to a certain extent, achieving the purpose of reducing costs and increasing efficiency.

Description

Technical Field

[0001] The present invention belongs to the technical field of oil and gas field development, and specifically relates to a method for integrating tight reservoir pressure injection and drive production ("pressure injection and drive production" is "pressure-injection-drive-production", which is the abbreviation of "fracturing, water injection, displacement, and oil production", and "pressure injection and drive production" is clear to those skilled in the art). Background Art

[0002] The Mahu tight conglomerate reservoir in the Junggar Basin is a low-porosity, ultra-low-permeability reservoir with undeveloped natural fractures and strong heterogeneity, requiring large-scale horizontal well volume fracturing for effective development. The horizontal well volume fracturing primary recovery rate in this area is low, only 10-12%, and the remaining oil between wells and fractures is difficult to effectively mobilize, with an average fracture network sweep rate of only 63%. Therefore, the need to improve the recovery rate in this area is very urgent.

[0003] It is difficult to improve the recovery rate of the tight sandstone conglomerate reservoir in Mahu. Conventional water injection to improve the recovery rate faces the problem of not being able to inject, drive, or produce. The worse the reservoir quality, the higher the driving pressure. At present, for old wells that are not fully transformed, repeated fracturing can be performed to improve the recovery rate. For horizontal wells with large well spacing, the method of drilling infill wells + volume transformation can be used to improve the overall recovery rate of the reservoir. However, there is a risk of changing the geostress field in the area and affecting the production of old wells. At present, the average single well fracturing and drilling costs of Mahu horizontal wells are high.

[0004] Therefore, it is urgent to study the technology of improving oil recovery by single fracturing. Under the new unconventional development model, recoverable reserves are mainly controlled by the fracture network. In view that the cost of proppant accounts for about 30% of the fracturing cost, the increase in the density of the proppant fracture network means a sudden increase in the cost of a single well. If only the volume of injected fluid is increased, the fluid enters the unsupported artificial fractures, which can increase the contact area between the fluid and the reservoir matrix, replenish formation energy, continuously form new microcracks, and also produce oil through imbibition, thereby improving the recovery rate.

[0005] There are many reservoir transformation methods disclosed in the prior art. For example, the patent application CN201710078828.2 discloses a zipper-type seam-laying dual-fracture horizontal well asynchronous water injection and oil production method. The asynchronous injection and production method of different wells can effectively displace the residual oil between wells, between seams and dead oil areas through zipper-type seams, thereby increasing the swept volume. This patent is for water injection after a period of production after fracturing, which cannot achieve the integrated transformation of "pressure-injection-drive-production", and it is difficult to overcome the problem of high water injection pressure in tight reservoirs.

[0006] The patent with application publication number CN201610253550.3 discloses a method for simultaneous water injection and oil production in multi-stage fracturing horizontal wells. It includes the following steps: fracturing horizontal wells in stages to form multiple fractures, using natural energy for production in the early stage of production, until the bottom hole pressure drops to the bubble point pressure, taking out the oil pipe, installing injection and production separation devices at the position of each odd-numbered fracture, installing injection valves at the position of each even-numbered fracture, opening perforations on the oil pipe corresponding to the positions of the odd-numbered fractures, putting the oil pipe back in place, closing the wellhead production valve, opening the injection valve, injecting water into the annular space of the casing, and the injected water flows through the guide pipe into the even-numbered fractures, opening the wellhead production valve, and the crude oil is produced from the odd-numbered fractures into the annulus formed by the guide pipe, casing and tubing, and then produced through the tubing, and at this time, water injection into the even-numbered fractures continues. This patent is for water injection after a period of production after fracturing, which cannot achieve integrated "pressure-injection-drive-production" and is difficult to overcome the problem of high water injection pressure in tight reservoirs.

[0007] The present invention aims to study an integrated reservoir transformation method of "pressure-injection-drive-production" to solve the technical problems of low primary recovery rate of volume fracturing of horizontal wells in Mahu tight conglomerate reservoir, difficulty in effectively mobilizing residual oil between wells and seams, and inability to inject, drive or produce oil by conventional water injection to enhance oil recovery. Summary of the invention

[0008] In order to overcome the above technical problems, the present invention provides a method for reservoir transformation integrating pressure injection, flooding and recovery of tight reservoirs. Based on the differentiated analysis and re-understanding of geological characteristics, numerical simulation of reservoirs and fractures is carried out, the fracturing and water injection technology and supporting process flow are optimized, and new fractures are formed through artificial fracture network displacement, the injection swept volume is expanded, the water drive pressure is reduced, the fracture network controlled reserves and the utilization degree are increased, and finally the purpose of significantly improving the recovery rate by one fracturing is achieved.

[0009] To achieve the above objectives, the technical solution provided by the present invention is as follows:

[0010] A method for integrating tight reservoir pressure injection, flooding and production, comprising the following steps:

[0011] (1) Based on the differential analysis of geological characteristics, determine the water drive flow direction and "sweet spot" of sandstone and conglomerate; determine the location of wells, fracturing method, horizontal section length and direction;

[0012] (2) Integrated reservoir engineering design: by detecting the real-time expansion law of fractures in three-dimensional visualization during fracturing and water injection construction, the coverage of the target layer can be determined, and the scale of water injection and well pattern layout can be optimized;

[0013] (3) Engineering design: Based on the boundary element displacement discontinuity method, finite volume method and implicit level set method, two-dimensional, pseudo-three-dimensional and three-dimensional numerical simulations of multi-hydraulic fracture expansion with full fluid-solid coupling are constructed. The stress interference between fractures, the change of fracturing fluid flow rate at the fracture entrance, the pressure drop of perforation holes and hole erosion, and the migration of solid particles in the fractures are comprehensively considered to realize the dynamic simulation of fractures during the fracturing process, and optimize the design of construction technology and water injection transformation parameters.

[0014] (4) Fracturing is performed on the designed horizontal wells, and the construction process is monitored in real time.

[0015] (5) Pressure-driven water injection is carried out on the horizontal wells after fracturing. After the water injection is completed, the well is shut down. After the shut-down is completed, the well is opened for self-flowing production, and the construction process is monitored in real time.

[0016] Preferably, in step (1), the fracturing method is to perform cementing bridge plug segmented volume fracturing according to the volume fracturing transformation concept;

[0017] Preferably, in step (2), the water injection adopts high / ultra-high pressure water injection after volume fracturing;

[0018] Preferably, in step (1) and step (3), the horizontal section is 500m to 2000m long, and the number of fracturing stages is 20-30.

[0019] Preferably, in step (1) and step (3), the length of the horizontal section is 1500 m and the number of fracturing stages is 20.

[0020] Preferably, in step (2) and step (3), the construction parameters in the fracturing process include fracturing scale, fracturing construction parameters, fracturing stages, and fracturing clusters;

[0021] Preferably, the fracturing operation displacement is controlled at 8-10m 3 / min, and the cluster spacing is 25-30m.

[0022] Preferably, the cluster spacing is 25 m.

[0023] Preferably, in step (2) and step (3), the length of the fracturing crack is ≤ the horizontal well spacing;

[0024] Preferably, in step (2) and step (3), the sand-carrying fluid in the fracturing process is slick water or nanoemulsion fracturing fluid;

[0025] Preferably, the sand-carrying fluid has a strength of 20 to 30 m 3 / m;

[0026] Preferably, in step (2) and step (3), the proppant used in the fracturing process is quartz sand that can withstand pressure and meet the required compressive strength.

[0027] Preferably, in step (2) and step (3), the ratio of the volume of the sand-carrying fluid to the volume of the proppant during the fracturing process is 15 to 25 m 3 / m 3 ;

[0028] Preferably, in step (4), the real-time monitoring content includes a fracturing construction curve.

[0029] Preferably, in step (4), the real-time monitoring content includes construction pressure, instantaneous displacement, amount of sand added in each stage of fracturing construction and amount of fluid entering the well.

[0030] Preferably, in step (2) and step (3), the water injection displacement range is 0.02-6.6m 3 / min, within the allowable range of construction pressure limit, increase the displacement as much as possible to reduce water injection time and improve construction efficiency.

[0031] Preferably, in step (2) and step (3), the water injection pressure cannot exceed the construction pressure limit. If it exceeds the construction pressure limit, the water injection displacement is immediately reduced to less than 0.5m 3 / min, stop construction and soak the well.

[0032] Preferably, in step (2) and step (3), the soaking time is determined according to the scale of fracturing, and is generally 7 to 20 days. During the soaking process, the change of the wellhead oil pressure should be observed in time, and the soaking is stopped when the oil pressure decreases and tends to be stable or the decrease is ≤0.1 MPa.

[0033] The longer the well is shut in, the longer the oil and water are replaced in the formation, and the better the effect is, but it is not economical. Therefore, during the first well shut-in, the shut-in time can be extended as much as possible to obtain more comprehensive oil pressure change data. During the later well shut-in, the well shut-in time can be determined based on the first well shut-in data. In actual operation, it needs to be adjusted according to the on-site conditions to achieve sufficient oil and water replacement and thus achieve maximum oil production.

[0034] Preferably, in step (2) and step (3), the amount of water injection is optimized and adjusted in real time according to the injection pressure.

[0035] Preferably, in step (2) and step (3), the injection water is slick water or nanoemulsion fracturing fluid or clean water.

[0036] Preferably, in step (5), the real-time monitoring content includes water injection pressure, cumulative water injection volume, pressure drop curve and water absorption index curve, etc.

[0037] Compared with the prior art, the technical advantages of the present invention are:

[0038] Aiming at the current situation that the volume fracturing of horizontal wells in the Mahu tight conglomerate oil reservoir has low primary recovery rate, the residual oil between wells and seams is difficult to effectively mobilize, and the conventional water injection to enhance oil recovery method cannot inject, drive or produce, the present invention provides an integrated reservoir transformation method of "pressure-injection-drive-production".

[0039] The present invention utilizes the fracture network formed after fracturing, and the artificial fractures increase the displacement area and swept volume, significantly improving the production capacity, making it possible to efficiently develop low-permeability oil reservoirs with water drive. Through its application in the Baikouquan Formation in the Mahu Ma 131 well area, it provides a solution for the efficient development of low-permeability and ultra-low-permeability conglomerate oil reservoirs in Mahu to improve the recovery rate. The process is simple, and pressure-driven water injection is implemented after fracturing to increase the volume of injected fluid. The fluid enters the unsupported artificial fractures, which can increase the contact area between the fluid and the reservoir matrix, replenish the formation energy, continuously form new micro-cracks, and also extract oil through the imbibition effect, thereby improving the recovery rate, saving the use of proppant for a single well, and reducing the development cost of a single well, so as to achieve the purpose of significantly improving the recovery rate by one fracturing. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 :Process flow chart;

[0041] Figure 2 : Comparison chart of production oil pressure curve;

[0042] The present invention will be further described with reference to the accompanying drawings and embodiments: DETAILED DESCRIPTION

[0043] The present invention is described below by specific examples to make the technical solution of the present invention easier to understand and grasp, but the present invention is not limited thereto. The experimental methods described in the following examples are conventional methods unless otherwise specified; the reagents and materials described are all commercially available unless otherwise specified.

[0044] Basic Example:

[0045] In view of the low recovery rate of horizontal well volume fracturing in the Mahu tight conglomerate reservoir, the difficulty in effectively mobilizing the remaining oil between wells and seams, and the inability to inject, drive, or produce oil by conventional water injection to improve oil recovery, an integrated reservoir transformation method of "pressure-injection-drive-production" is provided. This method utilizes the fracture network formed after fracturing. The artificial fractures increase the displacement area and swept volume, significantly improve the recovery rate of the reservoir, and make it possible to efficiently develop low permeability reservoirs with water drive. The method includes at least the following steps:

[0046] (1) Differential analysis and re-understanding of geological characteristics. First, we need to re-understand the geology, and conduct differential analysis and re-understanding of geological characteristics: sedimentary characteristics, structural characteristics, physical characteristics, microscopic pore throat characteristics, reservoir sensitivity and wettability, oil layer characteristics, small layer sand body distribution and thickness, interlayer distribution and thickness, small layer physical properties, small layer ground stress and rock mechanical parameters, ground stress direction, fluid physical properties and temperature and pressure system, oil test and production characteristics, etc., and then optimize the well network, well type, production method and production enhancement technology. The water drive flow direction of sandstone and conglomerate is inconsistent with the direction of the fracturing crack, and the direction of finding the "sweet spot" must be found. Re-understanding includes stress field measurement and natural fracture development, which can determine the location of the well, fracturing method, horizontal section length and direction.

[0047] The location, horizontal section length and direction of the well described in step (1) are mainly determined based on the reservoir development and remaining oil distribution. The specific method can be determined through geological modeling of the block.

[0048] The fracturing method described in step (1) is cementing bridge plug segmented volume fracturing based on the volume fracturing transformation concept.

[0049] (2) Integrated design of reservoir engineering. By detecting the real-time expansion law of three-dimensional fractures in the fracturing and water injection construction project, the coverage range of the target layer can be determined, and the scale of water injection and the well network layout can be optimized and adjusted; conventional water injection pressure cannot establish effective displacement, and high / ultra-high pressure water injection after volume fracturing should be adopted; the oil-water replacement mainly by imbibition during water drive requires a certain amount of imbibition time, so the water injection and well soaking time should be extended.

[0050] Among them, step (2) three-dimensional visualization of the real-time expansion law of fractures is achieved through numerical simulation technology, and the contents that need to be optimized mainly include water injection method, water injection timing, single well water injection volume, well holding time, and well opening time.

[0051] (3) Engineering design. Based on the boundary element displacement discontinuity method, finite volume method and implicit level set method, a two-dimensional, pseudo-three-dimensional and three-dimensional numerical simulation of multiple hydraulic fracture extension with full fluid-solid coupling is constructed. The stress interference between fractures, the change of fracturing fluid flow at the fracture entrance, the pressure drop of perforation holes and hole erosion, and the migration of solid particles in the fracture are comprehensively considered to achieve the dynamic simulation of the fracture during the fracturing process and optimize the design of construction technology and water injection transformation parameters.

[0052] (4) Fracturing the designed horizontal wells and monitoring the construction process in real time.

[0053] Among them, the optimization of fracturing construction parameters in step (4), including fracturing scale, fracturing construction parameters, segment cluster combination optimization design, etc., is derived from the simulation optimization in step (2), step (3) and the geological re-understanding in step (1). The specific preferred applicable conditions and requirements are as follows:

[0054] The horizontal section is 500m to 2000m long, preferably 1500m long, and has 20 fracturing sections.

[0055] The displacement of fracturing construction is controlled at 8m 3 / min.

[0056] The cluster spacing is 25m.

[0057] The fracture length designed in simulation cannot be greater than the horizontal well spacing.

[0058] The purpose is to cooperate with the next step of pressure drive water injection to maximize the role of sand-carrying fluid in replenishing formation energy and infiltration oil displacement. The sand-carrying fluid is preferably slick water or nanoemulsion fracturing fluid. The fluid strength of the sand-carrying fluid is 20-30m 3 / m.

[0059] In order to form a support seam of a certain length, the preferred proppant is quartz sand that can withstand pressure and meet the compressive strength requirements.

[0060] The ratio of the volume of sand-carrying fluid to the volume of proppant during fracturing is 15-25m 3 / m 3 ;

[0061] Real-time monitoring content includes fracturing construction curves. Furthermore, it is required to include construction pressure, instantaneous displacement, sand addition amount and fluid volume of each stage of fracturing construction, so as to provide reference for subsequent optimization design.

[0062] (5) The horizontal wells that have been hydraulically fractured are subjected to pressure-driven water injection, and the wells are shut down after the water injection is completed. After the wells are shut down, the wells are opened for self-flowing production. The construction process is monitored in real time.

[0063] The optimization of water injection construction parameters in step (4), including water injection method, water injection displacement, injection water volume, injection pressure, well soaking time, etc., is derived from the simulation in step (2) and step (3) and the geological re-understanding in step (1). The specific preferred applicable conditions and requirements are as follows:

[0064] The water injection displacement range is 0.02~6.6m 3 / min, within the construction pressure limit, increase the displacement as much as possible to reduce the water injection time and improve the construction efficiency. The water injection pressure cannot exceed the construction pressure limit. If it exceeds the construction pressure limit, immediately reduce the water injection displacement. The water injection displacement should be less than 0.5m 3 / min, stop the well soaking. The amount of injected water is optimized and adjusted in real time according to the injection pressure. The injected water is optimized to be slick water or nanoemulsion fracturing fluid or clean water. It aims to supplement the formation energy and drive oil through imbibition while further reducing costs. It aims to supplement the formation energy and drive oil through imbibition. The soaking time cannot be less than 7 days. During the soaking process, the changes in the wellhead oil pressure should be observed in time. When the oil pressure decreases to a stable level or the decrease is less than 0.1MPa, stop soaking. Since the longer the soaking time, the longer the replacement time of oil and water in the formation, the better the effect, but it is not economically cost-effective. Therefore, the shut-in time can be extended as much as possible during the first soaking to obtain more comprehensive oil pressure change data. In the later soaking, the soaking time can be determined based on the first soaking data. In actual operation, it needs to be adjusted according to the on-site conditions to achieve sufficient replacement of oil and water, thereby achieving maximum oil production. Real-time monitoring content includes water injection pressure, cumulative water injection volume, pressure drop curve and water absorption index curve.

[0065] The following describes the application of the integrated reservoir reconstruction method of the present invention to a reservoir in a specific block, and compares the development effects of using the method of the present invention and not using the method of the present invention.

[0066] Example 1

[0067] Block information: Well 1319 belongs to the Mahu block, with a reservoir depth of 2500-3100m. The lithology is mainly sandstone, with an average oil layer porosity of 7.87%, an average permeability of 1.03mD, and an average oil layer span of 12.17m. The average thickness of the oil layer is 8.24m, the maximum horizontal principal stress direction is near east-west, the horizontal minimum principal stress coefficient is 1.4-1.7, the reservoir type is lithology-tectonic reservoir, microcracks are not developed, and microseismic monitoring results show that the direction of artificial fractures is close to the east-west direction. The block was put into horizontal well development in 2013, and the "horizontal well + volume fracturing" development model achieved a breakthrough from 2016 to 2020, but the recovery rate of a single well after one fracturing is low.

[0068] Horizontal well 1319 is a horizontal well that adopts the "pressure-injection-drive-production" integrated reservoir transformation method of the present invention. The development method and transformation parameters are in line with the horizontal well development model and development concept of the area; the steps are as follows:

[0069] (1) Differential analysis and re-understanding of geological characteristics. First, we need to re-understand the geology, and conduct differential analysis and re-understanding of geological characteristics: sedimentary characteristics, structural characteristics, physical characteristics, microscopic pore throat characteristics, reservoir sensitivity and wettability, oil layer characteristics, small layer sand body distribution and thickness, interlayer distribution and thickness, small layer physical properties, small layer ground stress and rock mechanical parameters, ground stress direction, fluid physical properties and temperature and pressure system, oil test and production characteristics, etc., and then optimize the well network, well type, production method and production enhancement technology. The water drive flow direction of sandstone and conglomerate is inconsistent with the direction of the fracturing crack, and the direction of finding the "sweet spot" must be found. Re-understanding includes stress field measurement and natural fracture development, which can determine the location of the well, fracturing method, horizontal section length and direction.

[0070] The location, horizontal section length and direction of the well described in step (1) are mainly determined based on the reservoir development and remaining oil distribution. The specific method can be determined through geological modeling of the block.

[0071] The fracturing method described in step (1) is cementing bridge plug segmented volume fracturing based on the volume fracturing transformation concept, aiming to increase the well fracture controlled reserves as much as possible through dense cutting. The horizontal section described in step (1) is oriented nearly north-south, aiming to be as perpendicular as possible to the direction of the maximum horizontal principal stress, which is conducive to the initiation and expansion of the artificial main fracture. The length of the horizontal section described in step (1) is optimized to 1880m.

[0072] (2) Integrated design of reservoir engineering. By detecting the real-time expansion law of three-dimensional fractures in the fracturing and water injection construction project, the coverage range of the target layer can be determined, and the scale of water injection and the well network layout can be optimized and adjusted; conventional water injection pressure cannot establish effective displacement, and high / ultra-high pressure water injection after volume fracturing should be adopted; the oil-water replacement mainly by imbibition during water drive requires a certain amount of imbibition time, so the water injection and well soaking time should be extended.

[0073] Among them, step (2) three-dimensional visualization of the real-time expansion law of fractures is achieved through numerical simulation technology, and the contents that need to be optimized mainly include water injection method, water injection timing, single well water injection volume, well holding time, and well opening time.

[0074] The water injection method described in step (2) is optimized to continuous water injection. If the water injection pressure is too high, it is switched to intermittent water injection. The intermittent water injection cycle is one day of injection and one day of rest, aiming to shorten the water injection time as much as possible and save time cost. However, the longer the water injection time, the longer the replacement time of oil and water in the formation, and the better the effect. Therefore, the second option is intermittent water injection. The water injection timing described in step (2) is optimized to be immediately injected 7.5 hours after fracturing, aiming to wait for some cracks to close and avoid the distribution of injected water.

[0075] The distance from the supporting fracture network is too far, and the displacement and imbibition distance is too long. The single well water injection volume in step (2) is optimized to 30000m3 The well soaking time and well opening time need to be optimized in combination with steps (3) and (4).

[0076] (3) Engineering design. Based on the boundary element displacement discontinuity method, finite volume method and implicit level set method, a two-dimensional, pseudo-three-dimensional and three-dimensional numerical simulation of multiple hydraulic fracture extension with full fluid-solid coupling is constructed. The stress interference between fractures, the change of fracturing fluid flow at the fracture entrance, the pressure drop of perforation holes and hole erosion, and the migration of solid particles in the fracture are comprehensively considered to achieve the dynamic simulation of the fracture during the fracturing process and optimize the design of construction technology and water injection transformation parameters.

[0077] (4) Fracturing is performed on the designed horizontal wells and the construction process is monitored in real time.

[0078] Among them, the optimization of fracturing construction parameters in step (4), including fracturing scale, fracturing construction parameters, segment cluster combination optimization design, etc., is derived from the simulation optimization in step (2), step (3) and the geological re-understanding in step (1). The specific preferred applicable conditions and requirements are as follows:

[0079] The number of fracturing stages in step (3) and step (4) is optimized to 20, the number of clusters is optimized to 60, the cluster spacing is optimized to 30m, and the construction displacement is optimized to 11m 3 / min, the fracture length simulation optimization is 100m, the fracturing fluid is slick water fracturing fluid, the proppant is quartz sand, and the fluid addition strength is optimized to 21m 3 / m, liquid-sand ratio is optimized to 16m 3 / m 3 Real-time monitoring content includes fracturing construction curves. Furthermore, it is required to include construction pressure, instantaneous displacement, sand addition amount and fluid volume of each stage of fracturing construction, so as to provide reference for subsequent optimization design.

[0080] The design of the fracturing parameters in step (4) aims to achieve large-liquid-volume dense-cutting volume fracturing and form a fracture network for the implementation of step (5).

[0081] (5) The horizontal wells that have been hydraulically fractured are subjected to pressure-driven water injection, and the wells are shut down after the water injection is completed. After the wells are shut down, the wells are opened for self-flowing production. The construction process is monitored in real time.

[0082] The optimization of water injection construction parameters in step (4), including water injection method, water injection displacement, injection water volume, injection pressure, well soaking time, etc., is derived from the simulation in step (2) and step (3) and the geological re-understanding in step (1). The specific preferred applicable conditions and requirements are as follows:

[0083] During the water injection process, monitor the pressure change and change the displacement. Within the construction pressure limit, increase the displacement as much as possible to reduce the water injection time and improve the construction efficiency. The water injection pressure cannot exceed the construction pressure limit. If it exceeds the construction pressure limit, immediately reduce the water injection displacement. The water injection displacement should be less than 0.5m 3 / min, stop the construction and soak the well. The displacement range of the water injection during the whole water injection process is 0.02-6.6m 3 / min. The amount of injected water is optimized and adjusted in real time according to the injection pressure. The injected water is optimized to be slick water or nanoemulsion fracturing fluid or clean water. It aims to supplement the formation energy and drive oil through imbibition while further reducing costs. It aims to supplement the formation energy and drive oil through imbibition. The well shut-in time is optimized to 7 days. During the well shut-in process, the change of wellhead oil pressure should be observed in time. When the oil pressure decreases to a stable level or the decrease is less than 0.1MPa, the well shut-in is stopped. Since the longer the well shut-in time, the longer the replacement time of oil and water in the formation, the better the effect, but it is not economically cost-effective. Therefore, the shut-in time can be extended as much as possible during the first well shut-in to obtain more comprehensive oil pressure change data. In the later well shut-in time, the well shut-in time can be determined based on the first well shut-in data. In actual operation, it needs to be adjusted according to the on-site situation to achieve sufficient replacement of oil and water, thereby achieving maximum oil production. Real-time monitoring content includes water injection pressure, cumulative water injection volume, pressure drop curve and water absorption index curve.

[0084] Comparative Example 1

[0085] Well 1317 belongs to the Mahu block. Its stratigraphic position and reservoir physical parameters are similar to those of Well 1319, and it also uses horizontal well staged fracturing. The difference is that Well 1317 does not use the "pressure-injection-drive-production" integrated reservoir transformation.

[0086] Comparative Example 2

[0087] Well 1318 belongs to the Mahu block. Its stratigraphic position and reservoir physical parameters are similar to those of Well 1319, and it also uses horizontal well staged fracturing. The difference is that Well 1318 does not use the "pressure-injection-drive-production" integrated reservoir transformation.

[0088] Comparison of transformation effects

[0089] Comparing the production data of the three wells after exploitation can intuitively reflect the impact of differences in construction technology on the effect of fracturing transformation.

[0090] (1) Pressure comparison

[0091] The characteristic of the integrated reservoir transformation method of "pressure-injection-drive-production" is that water injection after pressure injection can greatly supplement the formation pressure. The oil pressure comparison of the three wells 1317, 1318 and 1319 during the production process (see Appendix) Figure 2 ).

[0092] The initial pressure of 1318 was relatively high, but it dropped rapidly after production began, and the pressure drop after 100 days of production was the lowest among the three wells. The initial production pressures of wells 1317 and 1319 were similar, but the pressure drop of well 1319 was small, and the pressure remained stable, which was the highest among the three wells.

[0093] Pressure comparison shows that the integrated reservoir transformation method of "pressure-injection-drive-production" can greatly supplement formation energy and maintain a higher production pressure.

[0094] (2) Production data comparison

[0095] Comparing the historical production data of 1317, 1318 and 1319 (Table 1) most directly reflects the effect of fracturing transformation on improving oil well productivity.

[0096] Table 1 Comparison of production data of wells 1317, 1318 and 1319

[0097]

[0098] The results showed that Well 1319 adopted post-fracture water injection, with the largest amount of fluid entering the well and the highest cumulative oil production. The daily oil production in the past month was high, indicating that the integrated fracturing reservoir transformation method of "pressure-injection-drive-production" can significantly improve production capacity and maintain stable oil production efficiency.

[0099] The above detailed description is a specific description of one feasible embodiment of the present invention. The embodiment is not intended to limit the patent scope of the present invention. Any equivalent implementation or modification that does not deviate from the present invention should be included in the scope of the technical solution of the present invention.

Claims

1. A method for integrating tight reservoir pressure injection and flooding, comprising the following steps: (1) Determine the water flow direction and "sweet spot" of sandstone and conglomerate based on differential analysis of geological characteristics; Determine the location of the well, the fracturing method, the length and direction of the horizontal section; the fracturing method is to perform cementing bridge plug segmented volume fracturing based on the volume fracturing transformation concept; (2) Integrated reservoir engineering design: by detecting the real-time expansion law of fractures in three-dimensional visualization during fracturing and water injection construction, the coverage of the target layer can be determined, and the scale of water injection and well network layout can be optimized; The water injection adopts high / ultra-high pressure water injection after volume fracturing, and the scale of water injection includes: water injection method, water injection timing, and water injection volume per well; (3) Fracturing engineering design: Based on the boundary element displacement discontinuity method, finite volume method and implicit level set method, two-dimensional, pseudo-three-dimensional and three-dimensional multi-hydraulic fracture expansion numerical simulation with full fluid-solid coupling is constructed. The stress interference between fractures, the change of fracturing fluid flow at the fracture entrance, the pressure drop and hole erosion of the perforation, and the migration of solid particles in the fracture are comprehensively considered to realize the dynamic simulation of the fracture during the fracturing process, and optimize the design of construction technology and water injection transformation parameters; (4) Fracturing the designed horizontal wells and monitoring the construction process in real time; (5) Implement pressure-driven water injection on the horizontal wells after fracturing, shut down the well after water injection, and open the well for self-flowing production after shutting down, and monitor the construction process in real time; The optimization content of step (2) also includes the well-keeping time and the well-opening time. The well-keeping time and the well-opening time need to be optimized in combination with steps (3) and (4).

2. The integrated reservoir transformation method according to claim 1, characterized in that: In step (4), the length of the horizontal section is 500m~2000m, and the number of fracturing stages is 20.

3. The integrated reservoir transformation method according to claim 2, characterized in that: In step (4), the horizontal section length is 1500m.

4. The integrated reservoir transformation method according to claim 1, characterized in that: In step (4), the fracturing operation displacement is controlled at 8-10 m 3 / min, and the cluster spacing is 25m.

5. The integrated reservoir transformation method according to claim 1, characterized in that: The simulated designed fracturing crack length is ≤ the horizontal well spacing; in step (4), the sand-carrying fluid in the fracturing process is slick water or nanoemulsion fracturing fluid, and the fluid strength is 25~30m 3 / m.

6. The integrated reservoir transformation method according to claim 5, characterized in that: In step (4), the proppant used in the fracturing process is quartz sand that can withstand pressure and meet the compressive strength requirements; the ratio of the volume of the sand-carrying fluid to the volume of the proppant during the fracturing process is 15-25m 3 / m 3 ; In step (5), the water injection displacement range is 0.02-6.6m³ / min. Within the allowable range of the construction pressure limit, the displacement is increased as much as possible to reduce the water injection time and improve the construction efficiency; The injection pressure cannot exceed the construction pressure limit. If it exceeds the construction pressure limit, the injection displacement shall be immediately reduced. When the injection displacement is lower than 0.5m³ / min, the construction shall be stopped and the well shall be soaked. The soaking time shall be 7 to 20 days. During the soaking process, the change of wellhead oil pressure shall be observed. When the oil pressure drop tends to be stable or the drop is ≤0.1MPa, the soaking shall be stopped.

7. The integrated reservoir transformation method according to claim 1, characterized in that: In step (5), the amount of water injection is optimized and adjusted in real time according to the injection pressure, and the water injection is slick water or nanoemulsion fracturing fluid or clean water.

8. The integrated reservoir transformation method according to claim 1, characterized in that: In step (4), the real-time monitoring content includes the fracturing construction curve.

9. The integrated reservoir transformation method according to claim 1, characterized in that: In step (4), the real-time monitoring content includes the construction pressure, instantaneous displacement, the amount of sand added in each stage of fracturing construction and the amount of fluid entering the well.

10. The integrated reservoir transformation method according to claim 1, characterized in that: In step (5), the real-time monitoring content includes water injection pressure, cumulative water injection volume, pressure drop curve and water absorption index curve.

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