Pump water injection energy complementing process suitable for low-permeability sandstone reservoir under-injection well

Abstract

The invention provides a pump water injection energy supplementing technology suitable for a low-permeability sandstone reservoir under-injection well. The pump water injection energy supplementing technology mainly solves the problem that the water drive development level is affected due to the fact that the effect of an existing low-permeability block plug removal and injection increasing measure is not ideal, and the proportion of a low-yield well is increased. Comprising the following steps that S1, according to well selection conditions of the skid-mounted pump water injection energy complementing process, an under-injection well is screened; s2, for the selected under-injection well, determining single-well and single-layer water supplementing amount and construction parameters; s3, preparation work before water injection construction is completed; and S4, on the basis of the determined single well and single layer water supplementing amount, skid-mounted pump water injection precise construction is conducted in cooperation with a separated layer water injection process pipe column. The pump water injection energy supplementation process is suitable for precise energy supplementation of a low-permeability sandstone reservoir under-injection well, fixed-layer precise concentrated energy supplementation is carried out in the mode that skid-mounted hydraulic piston injection pump equipment and a layered water injection process pipe column are matched for construction, and the pump water injection energy supplementation process has the advantages that energy supplementation according to needs, precise energy supplementation, concentrated energy storage and improvement of the in-layer use degree.

Description

Technical Field

[0001] The invention relates to the technical field of oil production engineering, and in particular to a pump water injection energy replenishment process suitable for under-injection wells in low-permeability sandstone reservoirs. Background Art

[0002] For low permeability blocks in oil fields, because their reservoirs have the characteristics of small pore throats, low permeability, large capillary resistance and strong sensitivity, as the development time becomes longer, the injection capacity of water injection wells in the blocks gradually decreases. To address this problem, a variety of injection measures have been carried out on site, such as acidizing and fracturing. Due to geological conditions, the acidizing effect is poor, the fracturing cost is high, and the effect of unblocking and increasing injection measures is not ideal. Commonly used unblocking and increasing injection measures, such as acidizing and fracturing, have poor governance effects in low permeability blocks, and the input-output ratio of measures is often lower than 1:1.5. However, general water replenishment has uneven distribution between layers and cannot achieve the purpose of replenishing energy on demand. At the same time, affected by the worsening water absorption of water injection wells year by year, the formation pressure of the block is on a downward trend, and the situation of insufficient injection is severe, which directly leads to an increase in the proportion of low-yield wells. The situation of "no injection and no production" at both ends of oil and water wells is very serious, affecting the level of water drive development. Summary of the invention

[0003] The technical problem to be solved by the present invention is to overcome the problem that the existing low-permeability block unblocking and injection measures in the background technology are not ideal, resulting in an increase in the proportion of low-yield wells and affecting the level of water drive development, and to provide a pump water injection energy replenishment process suitable for under-injected wells in low-permeability sandstone reservoirs. The pump water injection energy replenishment process is suitable for accurate energy replenishment of under-injected wells in low-permeability sandstone reservoirs, and has the characteristics of on-demand energy replenishment, accurate energy replenishment, centralized energy storage, and improved in-layer utilization.

[0004] The present invention solves the problem through the following technical solution: the pump water injection energy replenishment process applicable to under-injection wells in low-permeability sandstone reservoirs comprises the following steps:

[0005] S1: Screen under-injected wells according to the well selection conditions of the skid-mounted pump water injection and energy replenishment process;

[0006] S2: For the selected under-injected wells, determine the single well and single layer water replenishment volume Qi and construction parameters;

[0007] S3: Complete the preparation work before water injection construction;

[0008] S4: Based on the determined single-well and single-layer water replenishment volume Qi, precise water injection construction with skid-mounted pump is carried out in coordination with the stratified water injection process string.

[0009] Furthermore, the wells selected for the skid-mounted pump water injection and energy replenishment process in step S1 are: medium to high under-injection wells and wells with serious interlayer conflicts.

[0010] Furthermore, the under-injection well is defined as a well where the difference between the reservoir fracture pressure of the injection layer section of the injection well and the injection pressure at the wellhead is less than 0.5 MPa, and the well has one of the following conditions, and the continuous water injection time is more than 15 days:

[0011] 1) Daily injection volume ≤ 10m 3 , the daily actual water injection volume is less than 70% of the daily allocated water injection volume;

[0012] 2) 10m 3 <Daily injection volume≤50m 3 , daily actual water injection volume < 80% of daily allocated water injection volume; daily allocated water injection volume > 50m 3 , daily actual water injection volume is less than 85% of the daily allocated water injection volume.

[0013] Furthermore, the well selection conditions for the skid-mounted pump water injection and energy replenishment process in step S1 are:

[0014] The actual daily water injection volume is less than 65% of the daily allocated water injection volume;

[0015] The ratio of the actual water injection volume of a certain layer to the actual water injection volume of other layers is greater than 3.5.

[0016] Furthermore, the method for determining the single-layer water replenishment amount in step S2 is:

[0017] Combined with the degree of reservoir pressure deficit, current water injection level, well control volume, and driving difficulty, the water replenishment volume of each single layer is calculated for the purpose of increasing formation pressure;

[0018] The water replenishment calculation formula for each single layer is:

[0019] Single layer water replenishment formula Qi=f (x) ×V×γ+Q 目前注水程度

[0020] Where:f (x) =1-(P 目前连通油井地层压力 / P 原始地层压力 ) 2 / 3 ;

[0021] V=L×L×H 折算厚度 ×Φ×π / 9;

[0022] H 折算厚度 =H 有效 +(H 射开 -H 有效 ) / 3;

[0023] γ=(N 连通方向数 / 6) 1 / 2 ;

[0024] Q 目前注水程度 =(V 单层累计注水量 -V+V连通井层累计采出量 )×(1-γ);

[0025] Where: Q i is the water replenishment of a single layer; f (x) is the degree of deficit; V is the control volume; γ is the driving coefficient; Q 目前注水程度 The current level of water injection into the well;

[0026] L is the distance between connected oil and water wells, m;

[0027] φ is the porosity, a decimal (0 to 1);

[0028] V 单层累计注水量 is the cumulative water injection volume of a single layer, m 3 ;

[0029] V 连通井层累计采出量 is the cumulative production of connected wells, m 3 ;

[0030] N is the number of connected directions;

[0031] H 折算厚度 is the converted oil layer thickness, m;

[0032] H 有效 is the effective oil layer thickness, m;

[0033] H 射开 is the thickness of the perforated oil layer, m.

[0034] Furthermore, the water replenishment amount of the single well in step S2 is the sum of the water replenishment amounts of each single layer;

[0035] The formula for determining the water replenishment volume for a single well is: Q = ∑Qi;

[0036] Where: Q is the water replenishment volume of a single well.

[0037] Furthermore, the preparatory work before construction in step S3 includes:

[0038] Put water spouts in the test well to be replenished in the water layer, and put dead spouts in other layers;

[0039] Transfer the construction equipment to the well site for layout;

[0040] Connect the power supply and water source and test their safety and completeness;

[0041] Assemble skid mounted pump water injection system;

[0042] The pressure test of wellhead, manifold, valve group, etc. is 24.5MPa, and the pressure drop within 10 minutes is less than 0.7MPa, which is qualified.

[0043] Furthermore, the method for assembling the skid-mounted pump water injection system is:

[0044] Connect the liquid inlet end of the skid-mounted hydraulic piston injection pump equipment to the water reservoir;

[0045] The liquid outlet of the skid-mounted hydraulic piston injection pump equipment is connected to the wellhead of the under-injection well through a high-pressure pipeline.

[0046] Further, step S4, based on the determined single well and single layer water replenishment volume, performs a skid-mounted pump water injection construction process, including:

[0047] Connect to the ground equipment for pressure test and perform single-layer quantitative water injection with skid-mounted pump Q i During construction, the maximum injection pressure is less than the wellhead pressure;

[0048] After the single-layer construction is completed, the next step of layered fishing is carried out, and the layer is fished into a dead mouth. The dead mouth is pulled out at the next construction layer, and the preset quantitative Q of the layer is carried out. i During construction, the maximum injection pressure is less than the wellhead pressure;

[0049] After the single-layer construction is completed, repeat the previous step until the entire designed construction section is completed;

[0050] Inject on site according to the actual maximum displacement, and adjust the displacement in time according to the pressure changes during the construction process;

[0051] After completing the injection volume required by the design, normal injection will be carried out according to the original injection volume the next day.

[0052] Furthermore, the method of injecting at the actual maximum displacement on site and adjusting the displacement in time according to the pressure changes during the construction process is as follows:

[0053] Control the pressure rise rate to less than 1.0MPa / d, and the maximum wellhead pressure to about 20.0MPa;

[0054] When the pressure rises too fast, reduce the instantaneous injection displacement; when the pressure rises too slowly, increase the instantaneous injection displacement to maintain a stable trend of the injection pressure and reduce the fluctuation of the injection pressure;

[0055] The reference value for injection at the actual maximum displacement on site is 50-300m 3 / d.

[0056] Compared with the above background technology, the present invention has the following beneficial effects:

[0057] The present invention discloses a pump water injection energy replenishment process suitable for under-injection wells in low-permeability sandstone reservoirs, which is suitable for accurate energy replenishment of under-injection wells in low-permeability sandstone reservoirs. It adopts a skid-mounted hydraulic piston injection pump device and a layered water injection process pipe string for construction to carry out energy replenishment on demand in a fixed layer and accurate centralized energy replenishment, thereby increasing the maximum working pressure and construction displacement, and continuously operating for 24 hours. Under the conditions of high pressure difference and large displacement, different layers of the under-injection well are respectively centrally supplemented with preset metered clean water, which has the advantages of on-demand energy replenishment, accurate energy replenishment, centralized energy storage, and increased utilization within the layer.

[0058] The present invention has the characteristics of personalized construction, fast and safe construction, strong single-well targeting, and has the technical advantages of on-demand energy replenishment, precise energy replenishment, centralized energy storage, and improved intra-layer utilization.

[0059] By optimizing the under-injected well numbers, designing the single-well and single-layer water replenishment volume and construction parameters, the skid-mounted pump water injection construction is guided.

[0060] The application of this pump water injection and energy replenishment technology is suitable for the precise energy replenishment of under-injected wells in low-permeability sandstone reservoirs. It can greatly increase the underground water storage rate in the layer, effectively replenish the formation energy, enhance the driving power within the well group layer, improve the mobilization capacity within the well group layer, increase the swept volume, and improve the ability to tap the remaining oil in the potential layer.

[0061] Commonly used measures for unblocking and increasing injection, such as acidification and fracturing, have poor effects in the treatment of low permeability blocks, and the input-output ratio of the measures is often lower than 1:1.5. The general water replenishment has uneven distribution among layers and cannot achieve the purpose of replenishing energy on demand. However, the skid-mounted pump water injection and energy replenishment process of the present invention can be reused after the skid-mounted pump equipment is invested once. Only labor costs and electricity costs are required to personalize energy replenishment according to the under-injection amount of the injection well. The measures have stable effects and can achieve the purpose of "how much is lacking, how much is replenished". The input-output ratio is above 1:2, which effectively replenishes the formation energy, improves the water injection effect of low permeability blocks, achieves injection-production balance, improves the recovery degree of the block, and realizes efficient development of the oil field. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] Attached Figure 1 The present invention discloses a pump water injection energy replenishment process block diagram suitable for under-injection wells in low-permeability sandstone reservoirs;

[0063] Attached Figure 2 This is a schematic diagram of the well site construction layout of the skid-mounted pump water injection equipment of the present invention. Specific implementation method:

[0064] The present invention will be further described below in conjunction with the accompanying drawings and embodiments:

[0065] As attached Figure 1 As shown, the present invention discloses a pump water injection energy replenishment process suitable for under-injection wells in low-permeability sandstone reservoirs, comprising the following steps:

[0066] S1: Screen under-injected wells according to the well selection conditions of the pump water injection and energy replenishment process;

[0067] The well selection conditions of the pump water injection energy replenishment process include the following steps:

[0068] The wells selected for the pump water injection energy replenishment technology are medium to highly under-injected wells and wells with serious interlayer conflicts.

[0069] The well selection conditions for the pump water injection and energy replenishment process are one of the following:

[0070] 1) The actual daily water injection volume is less than 65% of the daily allocated water injection volume;

[0071] 2) The ratio of the actual water injection volume of a certain layer to the actual water injection volume of other layers is greater than 3.5;

[0072] The definition of an under-injection well is: except for injection wells that are planned to be shut down or controlled, an injection well is defined as an under-injection well if the difference between the reservoir fracture pressure of the injection layer section of the injection well and the wellhead injection pressure is less than 0.5MPa and one of the following conditions exists and lasts for more than 15 days.

[0073] 1) Daily injection volume ≤ 10m 3 , the daily actual water injection volume is less than 70% of the daily allocated water injection volume;

[0074] 2) 10m 3 <Daily injection volume≤50m 3 , the daily actual water injection volume is less than 80% of the daily allocated water injection volume;

[0075] 3) Daily injection volume>50m 3 , daily actual water injection volume is less than 85% of the daily allocated water injection volume.

[0076] S2: For the selected under-injected wells, determine the single well and single layer water replenishment volume Qi and construction parameters;

[0077] Combined with the degree of reservoir pressure deficit, current water injection degree, water well control volume, driving difficulty (connection direction, well spacing, permeability, porosity), and intra-layer differences (effective reservoir thickness and effective porosity), the water replenishment volume of each single layer is calculated for the purpose of increasing formation pressure. The single-layer water replenishment volume formula is as follows:

[0078] Qi=f (x) ×V×γ+Q 目前注水程度

[0079] Where: Q i is the water replenishment of a single layer; f (x) is the degree of deficit; V is the control volume; γ is the driving coefficient; Q 目前注水程度 The current level of water injection into the well;

[0080] The amount of water replenishment required for a single well, that is, the total amount of water replenishment for each single layer, is the amount of water replenishment required for a single well.

[0081] S3: Complete the preparatory work before water injection construction, such as Figure 2 As shown, specifically including:

[0082] Assemble the skid-mounted pump water injection equipment; connect the skid-mounted hydraulic piston injection pump to the water storage tank, and the test team will cast out the water nozzle at the stratum to be replenished with water; connect it to the wellhead of the under-injection well through a high-pressure pipeline, and test the pressure of the wellhead, manifold, valve group, etc. at 24.5MPa. The pressure drop within 10 minutes is considered qualified if it is less than 0.7MPa.

[0083] S4: Based on the determined single-well and single-layer water replenishment volume Qi, the precise construction process of skid-mounted pump water injection in cooperation with the stratified water injection process string is as follows:

[0084] The maximum injection pressure is less than the wellhead pressure. The actual maximum displacement is injected on site, and the reference value is 50-300m 3 / d, timely adjust the displacement according to the pressure changes during the construction process. After completing the required injection volume, inject normally according to the original injection volume the next day.

[0085] Example 1

[0086] Screening the under-injected well N-1 in the low-permeability M block outside Daqing Oilfield. The well is located in the L fault block. The whole well perforates 8 sedimentary units. In the initial stage of production, the daily injection is 30m 3 , actual daily injection is 14m 3 , in line with the "10m 3 <Daily injection volume≤50m 3 , the daily actual water injection volume is less than 80% of the daily allocated water injection volume”; the pump water injection energy replenishment construction well selection condition meets the “daily actual water injection volume is less than 65% of the daily allocated water injection volume”; the well has a cumulative water injection of 2.4×10 4 m 3 , due to the problem of insufficient injection, the water injection was affected by 1.24×10 4 m 3 , resulting in a serious lack of formation energy. There are four oil wells connected to the surrounding area, with a cumulative liquid production of 0.2652×10 4 t, meet the well selection conditions for skid-mounted pump water injection and energy replenishment technology;

[0087] b. Design the water replenishment volume Qi for a single well and a single layer; combine the pressure deficit of the oil layer, the current water injection level, the volume controlled by the water well, the driving difficulty (connection direction, well spacing, permeability, porosity), and the intra-layer difference (effective thickness and effective porosity of the reservoir) to increase the formation pressure and calculate the water replenishment volume for each single layer. The formula is as follows:

[0088] Single layer water replenishment formula Qi=f (x) ×V×γ+Q 目前注水程度

[0089] Where:f (x) =1-(P 目前连通油井地层压力 / P 原始地层压力 ) 2 / 3 ;

[0090] V=L×L×H 折算厚度 ×Φ×π / 9;

[0091] H 折算厚度 =H 有效 +(H 射开 -H 有效 ) / 3;

[0092] γ=(N 连通方向数 / 6) 1 / 2 ;

[0093] Q 目前注水程度 =(V 单层累计注水量 -V+V 连通井层累计采出量 )×(1-γ);

[0094] Where: Q i is the water replenishment of a single layer; f (x) is the degree of deficit; V is the control volume; γ is the driving coefficient; Q 目前注水程度 The current level of water injection into the well;

[0095] L is the distance between connected oil and water wells, m;

[0096] φ is the porosity, a decimal (0 to 1);

[0097] V 单层累计注水量 is the cumulative water injection volume of a single layer, m 3 ;

[0098] V 连通井层累计采出量 is the cumulative production of connected wells, m 3 ;

[0099] N is the number of connected directions;

[0100] H 折算厚度 is the converted oil layer thickness, m;

[0101] H 有效 is the effective oil layer thickness, m;

[0102] H 射开 is the thickness of the perforated oil layer, m.

[0103] The total amount of water replenishment for each single layer is the amount of water replenishment required for a single well:

[0104] The formula for determining the water replenishment volume for a single well is: Q = ∑Qi;

[0105] Where: Q is the water replenishment volume of a single well.

[0106] The basic data of each layer of a single well in the above formula are shown in Table 1; the calculation and input data of each layer of a single well are shown in Table 2.

[0107] Table 1

[0108]

[0109] Table 2

[0110]

[0111] c. Prepare the skid-mounted hydraulic piston injection pump and supporting equipment, connect the skid-mounted hydraulic piston injection pump to the water storage tank, and the test team will cast out the water nozzle at the stratum to be replenished, connect it to the wellhead of the under-injection well through a high-pressure pipeline, and test the pressure of the wellhead, manifold, valve group, etc. at 24.5MPa. The pressure drop within 10 minutes is qualified if it is less than 0.7MPa.

[0112] d. Connect the skid-mounted pump water injection equipment and the ground pipeline to test the water nozzle. First, construct the first layer PI1, and the other two layers will be dead nozzles. The construction pressure is 20.2MPa and the instantaneous injection volume is 9.2m 3 / h, the construction period is 8 days, and the cumulative injection volume is 1688m 3 , completed the first floor construction;

[0113] e. Test the water nozzle and construct the second layer PI2. The other two layers are dead nozzles. The construction pressure is 20.1MPa and the instantaneous injection volume is 9.6m 3 / h, the construction period is 11 days, and the cumulative injection volume is 2391m 3 , completed the second floor construction;

[0114] f. Test the water nozzle and construct the third layer PI4. The other two layers are dead nozzles. The construction pressure is 19.5MPa and the instantaneous injection volume is 10.9m 3 / h, the construction period is 8 days, and the cumulative injection volume is 1829m 3 , completed the construction of the third floor;

[0115] g. After the injection is completed, preparations are made to resume conventional water injection. The basic data of the well, the injection pressure and speed during the construction process, and other data are imported into the CMG numerical simulation software. The time for resuming water injection of the well is predicted through calculation. The wellhead pressure is continuously observed on site, and the time for resuming water injection is determined by actual measurement;

[0116] h. After the test, the well group effect was tracked and observed. The initial daily fluid increase of the connected well group was 2.7m 3 , with a daily oil increase of 2.1t, an effective period of 423 days, a cumulative oil increase of 1,035t, and a significant oil increase effect.

[0117] It should be noted that the embodiments described above are only used to explain the present invention and do not constitute any limitation to the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory words, rather than restrictive words. The present invention may be modified as specified within the scope of the claims of the present invention, and the present invention may be revised without departing from the scope and spirit of the present invention. Therefore, the content of the present invention is not limited to the examples listed, and any equivalent changes taken by ordinary technicians in the field of the present invention by reading the specification of the present invention to the technical solution of the present invention are all covered by the claims of the present invention.

Claims

1. A pump water injection energy replenishment process suitable for under-injection wells in low-permeability sandstone reservoirs, characterized by: The following steps are involved: S1: Screen under-injected wells according to the well selection conditions of the skid-mounted pump water injection and energy replenishment process; S2: For the selected under-injected wells, optimize the design to determine the single well and single layer water replenishment volume Qi and construction parameters; S3: Complete the preparation work before water injection construction; S4: Based on the determined single-well and single-layer water replenishment volume Qi, precise water injection construction with skid-mounted pump is carried out in coordination with the stratified water injection process string.

2. The pump water injection energy replenishment process applicable to under-injection wells in low permeability sandstone reservoirs according to claim 1 is characterized in that: The wells selected for the skid-mounted pump water injection and energy replenishment process in step S1 are: medium to high under-injection wells and wells with serious interlayer conflicts.

3. The pump water injection energy replenishment process applicable to under-injection wells in low permeability sandstone reservoirs according to claim 2 is characterized in that: The under-injection well is defined as a well where the difference between the reservoir fracture pressure of the injection layer section of the injection well and the injection pressure at the wellhead is less than 0.5 MPa, and the well has one of the following conditions, and the continuous water injection time is more than 15 days: 1) Daily injection volume ≤ 10m 3 , the daily actual water injection volume is less than 70% of the daily allocated water injection volume; 2) 10m 3 <Daily injection volume≤50m 3 , daily actual water injection volume < 80% of daily allocated water injection volume; daily allocated water injection volume > 50m 3 , daily actual water injection volume is less than 85% of the daily allocated water injection volume.

4. The pump water injection energy replenishment process applicable to under-injection wells in low permeability sandstone reservoirs according to claim 3 is characterized in that: The well selection conditions of the skid-mounted pump water injection and energy replenishment process in step S1 are: The actual daily water injection volume is less than 65% of the daily allocated water injection volume; The ratio of the actual water injection volume of a certain layer to the actual water injection volume of other layers is greater than 3.

5.

5. The pump water injection energy replenishment process applicable to under-injection wells in low permeability sandstone reservoirs according to claim 1 is characterized in that: The method for determining the single-layer water replenishment amount in step S2 is: Combined with the degree of reservoir pressure deficit, current water injection level, well control volume, and driving difficulty, the water replenishment volume of each single layer is calculated for the purpose of increasing formation pressure; The water replenishment calculation formula for each single layer is: Qi=f (x) ×V×γ+Q 目前注水程度 Where:f (x) =1-(P 目前连通油井地层压力 / P 原始地层压力 ) 2 / 3 ; H=L×L×H 折算厚度 ×Φ×π / 9; H 折算厚度 =H 有效 +(H 射开 -H 有效 ) / 3; γ=(N 连通方向数 / 6) 1 / 2 ; Q 目前注水程度 =(V 单层累计注水量 -V+V 连通井层累计采出量 )×(1-γ); Where: Q i is the water replenishment of a single layer; f (x) is the degree of deficit; V is the control volume; γ is the driving coefficient; Q 目前注水程度 The current level of water injection into the well; L is the distance between connected oil and water wells, m; φ is the porosity, a decimal (0 to 1); V 单层累计注水量 is the cumulative water injection volume of a single layer, m 3 ; V 连通井层累计采出量 is the cumulative production of connected well layers, m 3 ; N is the number of connected directions; H 折算厚度 is the converted oil layer thickness, m; H 有效 is the effective oil layer thickness, m; H 射开 is the thickness of the perforated oil layer, m.

6. The pump water injection energy replenishment process applicable to under-injection wells in low permeability sandstone reservoirs according to claim 5 is characterized in that: The water replenishment amount of a single well in step S2 is the sum of the water replenishment amounts of each single layer; The formula for determining the water replenishment volume for a single well is: Q = ∑Qi; Where: Q is the water replenishment volume of a single well.

7. The pump water injection energy replenishment process applicable to under-injection wells in low permeability sandstone reservoirs according to claim 1 is characterized in that: The preparatory work before construction in step S3 includes: Put water spouts in the test well to be replenished in the water layer, and put dead spouts in other layers; Transfer the construction equipment to the well site for layout; Connect the power supply and water source and test their safety and completeness; Assemble skid mounted pump water injection system; The wellhead, manifold and valve group are tested for pressure of 24.5MPa, and the pressure drop within 10 minutes is less than 0.7MPa, which is qualified.

8. The pump water injection energy replenishment process applicable to under-injection wells in low permeability sandstone reservoirs according to claim 7 is characterized in that: To assemble the skid mounted pump water injection system: Connect the liquid inlet end of the skid-mounted hydraulic piston injection pump equipment to the water reservoir; The liquid outlet of the skid-mounted hydraulic piston injection pump equipment is connected to the wellhead of the under-injection well through a high-pressure pipeline.

9. The pump water injection energy replenishment process applicable to under-injection wells in low permeability sandstone reservoirs according to claim 6 is characterized in that: Step S4: Based on the determined single well and single layer water replenishment volume, the skid-mounted pump water injection construction process includes: Connect to the ground equipment for pressure test and perform single-layer quantitative water injection with skid-mounted pump Q i During construction, the maximum injection pressure is less than the wellhead pressure; After the single-layer construction is completed, the next step of layered fishing is carried out, and the layer is fished into a dead mouth. The dead mouth is pulled out at the next construction layer, and the preset quantitative Q of the layer is carried out. i During construction, the maximum injection pressure is less than the wellhead pressure; After the single-layer construction is completed, repeat the previous step until the entire designed construction section is completed; Inject on site according to the actual maximum displacement, and adjust the displacement in time according to the pressure changes during the construction process; After completing the injection volume required by the design, normal injection will be carried out according to the original injection volume the next day.

10. The pump water injection energy replenishment process applicable to under-injection wells in low permeability sandstone reservoirs according to claim 9 is characterized in that: The method of injecting according to the actual maximum displacement on site and adjusting the displacement in time according to the pressure changes during the construction process is as follows: Control the pressure rise rate to less than 1.0MPa / d, and the maximum wellhead pressure to about 20.0MPa; When the pressure rises too fast, reduce the instantaneous injection displacement; when the pressure rises too slowly, increase the instantaneous injection displacement to maintain a stable trend of the injection pressure and reduce the fluctuation of the injection pressure; The reference value for injection at the actual maximum displacement on site is 50~300m 3 / d.

Images