A method for enhancing production by dense low-permeability sandstone sand-assisted pressure flooding
By optimizing fracturing process parameters and injecting active water, the problems of low permeability and uneven fractures in tight sandstone reservoirs were solved, enabling precise reservoir modification and efficient development, and improving oil recovery.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- CHINA PETROLEUM & CHEMICAL CORP
- Filing Date
- 2025-12-10
- Publication Date
- 2026-06-02
AI Technical Summary
Tight sandstone reservoirs have low permeability, strong heterogeneity, and complex thin interbedded structures. Conventional stimulation methods result in uneven proppant settlement and fracture extension, leading to poor fracturing effects and hindering efficient development.
Numerical simulation was used to optimize fracturing process parameters. Functional active water and a low-porosity flow-limiting perforation process were used. Low-volume drag-reducing water and active water were injected alternately at low flow rates to promote microfracture extension and optimize the fracture network. Active water was injected through slugs to replenish formation energy, control fracture extension, and improve seepage capacity.
It achieved precise reservoir modification, enhanced permeability, improved crude oil recovery, achieved good energy replenishment and oil washing effects, and significantly improved production and production stability.
Smart Images
Figure CN122129233A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a sand-filled pressure drive method, and more specifically, a sand-filled pressure drive method for increasing production capacity in dense, low-permeability sandstone. Background Technology
[0002] The tight sandstone reservoirs in northern Jiangsu Province exhibit poor reservoir properties, low permeability, strong heterogeneity, and poor connectivity, necessitating reservoir stimulation for effective development. They also feature thin interbedded layers, typically less than 10 meters thick, with complex combinations with interlayers (mudstone or siltstone), forming a "sand-mud-sand" alternating thin interbedded structure. Significant lithological differences make optimizing fracturing parameters difficult, limiting reservoir stimulation effectiveness. Conventional stimulation methods employ high displacement and proppant loading to create propped fractures and improve fracturing efficiency. However, for thin interbedded tight sandstone, the small stress difference between interlayers and producing layers makes fracture height easily uncontrollable under high displacement fracturing, leading to excessive extension into non-target producing layers. Furthermore, proppant settles towards the fracture bottom due to gravity during migration, with a stronger settling trend at the fracture tip, preventing proppant from reaching the tip and resulting in fracture closure due to lack of proppant filling. To improve the filling effect of proppant in fractures, both domestically and internationally, a combination of proppants with different particle sizes and densities is commonly used to create propped long fractures and achieve effective support for fracture height. However, due to the significant longitudinal extension of fracture height in thin interbedded layers under high displacement conditions, it is difficult to solve the problem of effective support for fracture height using a combination of proppants with different particle sizes and densities. Furthermore, the application of conventional fracturing techniques to stimulate tight, low-permeability oil reservoirs results in a small affected area and a rapid decline in production after fracturing, leading to an overall low-production and low-efficiency level that cannot meet the needs of reservoir stimulation and hinders efficient development. Summary of the Invention
[0003] Therefore, it is necessary to provide a method for increasing production capacity by adding sand to dense, low-permeability sandstone and pressurizing it to address the aforementioned technical problems.
[0004] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: A method for increasing production capacity by adding sand pressure drive to tight, low-permeability sandstone, comprising the following steps: Step S1: Collect parameters of tight, low-permeability sandstone reservoirs and use numerical simulation software to optimize and simulate the fracturing process parameters of thin interbedded layers; Step S2: Based on the reservoir's physical properties and wettability characteristics, select the functional active water that is compatible with the reservoir; Step S3: Based on the thickness of each thin reservoir, optimize the perforation parameters using a low-perforation flow-limiting process and carry out the perforation operation; Step S4: Wellbore ventilation and flushing, run tubing and fracturing string, and set packer; Step S5: Low-volume pre-injection of active water without proppant; Step S6: The injection of low-viscosity drag-reducing water fracturing fluid with proppant at low flow rate and the injection of active water without proppant at low flow rate are alternately circulated until 40% of the designed total proppant volume is completed; Step S7: Use low-flow-rate pumps to inject large-scale active water to promote the extension of microfractures in the distant reservoir rocks. Step S8: Repeat the alternating injection in step S6, gradually increasing the sand ratio and drag-reducing water viscosity until the designed total sand volume is completed, replacing 1.5 times the wellbore volume of active water, and completing the sand injection pressure drive. Step S9: After pressure is applied, the well is shut down and the wellhead pressure is recorded every half hour. After the wellhead pressure stabilizes, a blowout test is performed, and the pump is then put into production.
[0005] In a preferred embodiment, in step S1, data such as reservoir rock mechanics parameters, geostress parameters, and oil layer thickness are collected, and hydraulic fracturing optimization design software is used to simulate fracturing process parameters to determine the fracturing pumping procedure.
[0006] As a preferred embodiment, in step S2, based on the physical properties and wettability characteristics of the reservoir, the laboratory evaluation selects functional active water that is compatible with the reservoir of the well to be fractured, which can improve the effective permeability of the core matrix and at the same time has the functions of oil washing and wettability modification.
[0007] As a preferred embodiment, in step S3, under low displacement, the number of perforations is optimized by adopting a low-perforation flow-limiting process according to the thickness of each thin layer, with 5 to 8 perforations per layer.
[0008] In a preferred embodiment, in step S5, the low discharge rate is 0.5-1 m³ / min, which promotes the extension of microfractures in the reservoir rock.
[0009] As a preferred embodiment, in step S6, the low discharge rate is 1-1.5 m3 / min, which effectively controls the hydraulic fracture height, reduces the influence of the lower high-stress layer and water layer, and realizes precise intra-layer modification of the reservoir.
[0010] As a preferred embodiment, in step S6, the injection pressure is changed cyclically by alternating small-volume injection to avoid excessive or irregular expansion of cracks caused by large-volume injection. This causes fatigue damage to the rock under alternating stress, forming a more uniform crack network, significantly expanding the oil drainage radius, and forming a crack geometry that better meets the design requirements.
[0011] In a preferred embodiment, in step S7, active water is injected to replenish formation energy, change the wettability of the rock surface, enhance the seepage capacity of the target section, improve the crude oil recovery rate, and achieve the effect of integrated energy replenishment and oil washing.
[0012] In a preferred embodiment, the proppant is quartz sand with a particle size of 70 / 200 mesh, which improves the effective support of the proppant in the distal crack.
[0013] As a preferred embodiment, the low-viscosity drag-reducing water fracturing fluid is a 0.1% drag-reducing agent fracturing fluid with a viscosity of 6-8 mPa·s.
[0014] In a preferred embodiment, the drag-reducing agent is a polyacrylamide suspension emulsion.
[0015] In a preferred embodiment, the activated water comprises, by volume, the following components: Synergist, 0.1%–0.3%; Anti-swelling agent, 0.1%–0.2%; Fungicide, 0.01%–0.02%; The rest is water.
[0016] In a preferred embodiment, the synergist is polyoxyethylene fatty alcohol ether ester sulfonate, the anti-swelling agent is potassium chloride salt, and the bactericide is a quaternary ammonium salt bactericide.
[0017] Compared with the prior art, the present invention has the following beneficial effects: This invention provides a method for enhancing reservoir energy and production in tight, low-permeability sandstone formations through sand-filled hydraulic fracturing. This method optimizes the pumping procedure by precisely simulating the impact of fracturing displacement on fracture propagation in thin, interbedded tight sandstone formations. It effectively controls fracture height using low-displacement fracturing fluid, resulting in short and wide fractures, preventing excessive fracture extension, reducing the influence of lower high-pressure and water layers, and achieving precise control of reservoir stimulation. Simultaneously, the method injects active water through a slug filler to replenish formation energy, altering rock surface wettability, enhancing the permeability of the target formation, and improving oil recovery, achieving good energy replenishment and oil washing effects. Attached Figure Description
[0018] To more clearly illustrate the solutions in this invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.
[0019] Figure 1 This is a simulation diagram of fracture propagation in a thin interbedded sandstone reservoir.
[0020] Figure 2 This is a schematic diagram of the sand-assisted pressure drive construction tubing of the present invention. Detailed Implementation
[0021] To enable those skilled in the art to better understand the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.
[0022] The method for increasing production capacity by adding sand pressure drive to tight, low-permeability sandstone includes the following steps: Step S1: Collect parameters of tight, low-permeability sandstone reservoirs and use numerical simulation software to optimize and simulate the fracturing process parameters of thin interbedded layers; Step S2: Based on the reservoir's physical properties and wettability characteristics, select the functional active water that is compatible with the reservoir; Step S3: Based on the thickness of each thin reservoir, optimize the perforation parameters using a low-perforation flow-limiting process and carry out the perforation operation; Step S4: Wellbore ventilation and flushing, run tubing and fracturing string, and set packer; Step S5: Low-volume pre-injection of active water without proppant; Step S6: The injection of low-viscosity drag-reducing water fracturing fluid with proppant at low flow rate and the injection of active water without proppant at low flow rate are alternately circulated until 40% of the designed total proppant volume is completed; Step S7: Use low-flow-rate pumps to inject large-scale active water to promote the extension of microfractures in the distant reservoir rocks. Step S8: Repeat the alternating injection in step S6, gradually increasing the sand ratio and drag-reducing water viscosity until the designed total sand volume is completed, replacing 1.5 times the wellbore volume of active water, and completing the sand injection pressure drive. Step S9: After pressure is applied, the well is shut down and the wellhead pressure is recorded every half hour. After the wellhead pressure stabilizes, a blowout test is performed, and the pump is then put into production.
[0023] In step S1, data such as reservoir rock mechanics parameters, geostress parameters, and oil layer thickness are collected, and hydraulic fracturing optimization design software is used to simulate fracturing process parameters to determine the fracturing pumping procedure.
[0024] In step S2, based on the physical properties and wettability characteristics of the reservoir, the laboratory evaluation selects functional active water that is compatible with the reservoir of the well to be fractured. This water can improve the effective permeability of the core matrix and also has the functions of oil washing and wettability modification.
[0025] In step S3, under low flow rate, the number of perforations is optimized by adopting a low-perforation flow-limiting process according to the thickness of each thin layer, with 5 to 8 perforations per single layer.
[0026] In step S5, the low discharge rate is 0.5-1 m3 / min, which promotes the extension of microfractures in the reservoir rock.
[0027] In step S6, the low discharge rate is 1-1.5 m3 / min, which effectively controls the hydraulic fracture height, reduces the impact of the lower high-stress layer and water layer, and achieves precise intra-layer modification of the reservoir.
[0028] In step S7, active water is injected to replenish formation energy, change the wettability of the rock surface, enhance the seepage capacity of the target section, improve the crude oil recovery rate, and achieve the effect of integrated energy replenishment and oil washing.
[0029] It should be noted that the proppant is quartz sand with a particle size of 70 / 200 mesh, which improves the effective support of the proppant in the far end of the crack.
[0030] The low-viscosity drag-reducing water fracturing fluid is a fracturing fluid with a viscosity of 6-8 mPa·s and 0.1% drag-reducing agent. The drag-reducing agent is a polyacrylamide suspension emulsion.
[0031] It should be noted that activated water, by volume, includes: Synergist, 0.1%–0.3%; Anti-swelling agent, 0.1%–0.2%; Fungicide, 0.01%–0.02%; The remainder is water. The synergist is polyoxyethylene fatty alcohol ether ester sulfonate, the anti-swelling agent is potassium chloride salt, and the bactericide is a quaternary ammonium salt bactericide.
[0032] In step S6, the injection pressure is changed cyclically by alternating small-volume injection to avoid excessive or irregular expansion of cracks caused by large-volume injection. This causes fatigue damage to the rock under alternating stress, forming a more uniform crack network, significantly expanding the oil drainage radius, and creating a crack geometry that better meets design requirements.
[0033] The working method of this method for increasing production capacity by adding sand and pressure driving in dense, low-permeability sandstone is described below.
[0034] Taking Well A in northern Jiangsu as an example, the target formation is the Fusan Section 13-16 layer, with a well depth of 3066.9m to 3085.8m. The effective thickness of the oil layer is 7.2m, the thickness of a single layer is 0.9 to 4.9m, the span of the producing layer is 18.9m, the permeability interpreted by well logging is 0.45×10-3μm2-19.36×10-3μm2, and the effective permeability interpreted by well test is 1.2×10-3μm2, indicating that the reservoir has poor permeability.
[0035] The specific implementation steps are as follows: Step S1: Based on the reservoir's physical properties and wettability characteristics, select active water that can improve the effective permeability of the core matrix and simultaneously have the functions of oil washing and wettability modification. Step S2: Based on the rock mechanics parameters, geostress parameters and oil layer thickness of the thin interbedded tight sandstone reservoir in the Subei Basin, the process parameters are simulated using hydraulic fracturing optimization design software, and the pumping program is optimized, as shown in Table 1 below. Table 1 Construction Pumping Procedure
[0036] Step S3: Optimize the perforation parameters using a few-hole flow limiting process and perform the perforation operation, as shown in Table 2 below; Table 2 Perforation Parameters
[0037] Step S4: Wellbore ventilation and flushing, run in tubing L1 and fracturing string, and set packer L2.
[0038] Step S5: Use activated water, at a concentration of 0.5-1m 3 Inject 400 at a displacement of / min 3 ; Step S6: Inject 0.1% drag-reducing water and active water alternately in sequence, wherein the 0.1% drag-reducing water contains 100 / 200 mesh quartz sand; Step S7: Use activated water, according to 0.5-1m 3 Inject 1000 at a displacement of / min 3 ; Step S8: Inject using 0.2% drag-reducing water and activated water, wherein the 0.2% drag-reducing water contains 70 / 140 mesh quartz sand; Step S9: After pressure is applied, the well is shut down and the wellhead pressure is recorded every half hour. After the wellhead pressure stabilizes, a blowout test is performed, and the pump is then put into production.
[0039] To restore production to the old well, the fracturing process for layers 13-16 was optimized. This well has multiple thin fracturing layers with no significant vertical obstruction. To prevent excessive longitudinal fracture extension under high flow rates, the fracturing flow rate was set at 0.5-1.5 m³ / s. 3 / min, total liquid volume 2600m 3 Total sand volume: 50m³ 3 The composition of the proppant is as follows: 60% is clean water and 40% is low-viscosity fracturing fluid. The preferred proppant is a combination of 100 / 200 mesh quartz sand. This reduces construction risks and improves the effective support of the proppant in the far-end fracture.
[0040] The highest oil pressure during construction was 31.3 MPa. After the 100 / 200 mesh quartz sand was inserted into the formation, the oil pressure dropped from 31.3 MPa to 29.0 MPa. Subsequently, the construction pressure remained relatively stable at 27.0-28.0 MPa, and 50m of sand was successfully added. 3 After fracturing, the pump was put into operation, with an initial average production rate of 7.05 m³. 3 / d, oil production 3.2t / d, current average liquid production 2.1m 3 / d, with an oil production of 1.8t / d, and a cumulative increase of 579.8t in oil production.
[0041] Well B, located in the adjacent area, was constructed using conventional fracturing with proppant addition, with a displacement of 3.5-4 m³. 3 / min, using 40 / 70 mesh + 30 / 50 mesh low-density ceramsite with added sand for 50m 3 The large-scale fracturing operation achieved an average initial production rate of 6.8 m³ / s. 3 / d, oil production 2.6t / d, after 2 months of production the average liquid production dropped to 0.8m 3 / d, oil production dropped to 0.6t / d, with a cumulative increase of only 160.7t.
[0042] Therefore, compared with the adjacent well B, the thin interbedded reservoir in well A showed significant effects in increasing and stabilizing production after sand addition and pressure drive.
[0043] This invention provides a method for enhancing energy production in tight, low-permeability sandstone formations through sand-filled hydraulic fracturing. By precisely simulating the impact of fracturing displacement on fracture propagation in thin, interbedded tight sandstone formations, the method optimizes the process by injecting a certain amount of active water at a small displacement rate, followed by low-dispersion injection of low-viscosity fracturing fluid with sand, and then switching to a small displacement injection of a large amount of displacement fluid midway to induce micro-fractures in the distant reservoir. Further fracturing fluid injection with sand at a small displacement rate improves inter-layer dynamics. Simultaneously, active water is injected through a slug to replenish formation energy and enhance the permeability of the target section, achieving particularly good energy replenishment and oil washing effects in thin, interbedded reservoirs.
[0044] Obviously, the embodiments described above are only some embodiments of this application, and not all embodiments. The accompanying drawings show preferred embodiments of this application, but do not limit the patent scope of this application.
Claims
1. A method for increasing production capacity by adding sand pressure drive to tight, low-permeability sandstone, comprising the following steps: Step S1: Collect parameters of tight, low-permeability sandstone reservoirs and use numerical simulation software to optimize and simulate the fracturing process parameters of thin interbedded layers; Step S2: Based on the reservoir's physical properties and wettability characteristics, select the functional active water that is compatible with the reservoir; Step S3: Based on the thickness of each thin reservoir, optimize the perforation parameters using a low-perforation flow-limiting process and carry out the perforation operation; Step S4: Wellbore ventilation and flushing, run tubing and fracturing string, and set packer; Step S5: Low-volume pre-injection of active water without proppant; Step S6: The injection of low-viscosity drag-reducing water fracturing fluid with proppant at low flow rate and the injection of active water without proppant at low flow rate are alternately circulated until 40% of the designed total proppant volume is completed; Step S7: Use low-flow-rate pumps to inject large-scale active water to promote the extension of microfractures in the distant reservoir rocks. Step S8: Repeat the alternating injection in step S6, gradually increasing the sand ratio and drag-reducing water viscosity until the designed total sand volume is completed, replacing 1.5 times the wellbore volume of active water, and completing the sand injection pressure drive. Step S9: After pressure is applied, the well is shut down and the wellhead pressure is recorded every half hour. After the wellhead pressure stabilizes, a blowout test is performed, and the pump is then put into production.
2. The method for increasing production capacity by adding sand and pressure driving to dense, low-permeability sandstone according to claim 1, characterized in that, In step S1, data such as reservoir rock mechanics parameters, geostress parameters, and oil layer thickness are collected, and hydraulic fracturing optimization design software is used to simulate fracturing process parameters and determine the fracturing pumping procedure.
3. The method for increasing production capacity by adding sand and pressurizing the rock to enhance tight, low-permeability sandstone according to claim 1, characterized in that, In step S2, based on the physical properties and wettability characteristics of the reservoir, the laboratory evaluation selects functional active water that is compatible with the reservoir of the well to be fractured. This water can improve the effective permeability of the core matrix and also has the functions of oil washing and wettability modification.
4. The method for increasing energy production and improving yield in dense, low-permeability sandstone by pressure flooding with sand, as described in claim 1, is characterized in that... In step S3, under low flow rate, the number of perforations is optimized by adopting a low-perforation flow-limiting process according to the thickness of each thin layer, with 5 to 8 perforations per single layer.
5. The method for increasing production capacity by adding sand and pressure driving to dense, low-permeability sandstone according to claim 1, characterized in that, In step S5, the low displacement is 0.5-1m³. 3 / min, promoting the extension of microfractures in reservoir rocks.
6. The method for increasing production capacity by adding sand and pressurizing the rock to enhance tight, low-permeability sandstone according to claim 1, characterized in that, In step S6, the low displacement is 1-1.5m. 3 / min, effectively controlling the hydraulic fracture height, reducing the impact of the lower high-stress layer and water layer, and achieving precise intra-layer modification of the reservoir.
7. The method for increasing production capacity by adding sand and pressurizing the rock to enhance tight, low-permeability sandstone according to claim 1, characterized in that, In step S6, the injection pressure is changed cyclically by alternating small-volume injection to avoid excessive or irregular expansion of cracks caused by large-volume injection. This causes fatigue damage to the rock under alternating stress, forming a more uniform crack network, significantly expanding the oil drainage radius, and creating a crack geometry that better meets design requirements.
8. The method for increasing production capacity by adding sand and pressurizing the rock to enhance tight, low-permeability sandstone according to claim 1, characterized in that, In step S7, active water is injected to replenish formation energy, change the wettability of the rock surface, enhance the seepage capacity of the target section, improve the crude oil recovery rate, and achieve the effect of integrated energy replenishment and oil washing.
9. The method for increasing production capacity by adding sand and pressure driving to dense, low-permeability sandstone according to claim 4, characterized in that, The proppant is quartz sand with a particle size of 70 / 200 mesh, which improves the effective support of the proppant in the distal crack.
10. The method for increasing production capacity by adding sand and pressurizing the rock to enhance tight, low-permeability sandstone according to claim 1, characterized in that, The low-viscosity drag-reducing water fracturing fluid is a 0.1% drag-reducing agent fracturing fluid with a viscosity of 6-8 mPa·s.
11. The method for increasing production capacity by adding sand and pressurizing the rock to enhance tight, low-permeability sandstone according to claim 10, characterized in that, The drag-reducing agent is a polyacrylamide suspension emulsion.
12. The method for increasing production capacity by adding sand and pressure driving to dense, low-permeability sandstone according to claim 1, characterized in that, The activated water, by volume, comprises: Synergist, 0.1%–0.3%; Anti-swelling agent, 0.1%–0.2%; Fungicide, 0.01%–0.02%; The rest is water.
13. The method for increasing production capacity by adding sand and pressurizing the rock to enhance tight, low-permeability sandstone according to claim 12, characterized in that, The synergist is polyoxyethylene fatty alcohol ether ester sulfonate, the anti-swelling agent is potassium chloride salt, and the bactericide is a quaternary ammonium salt bactericide.