Blockage removing and injection increasing method for strong production and strong well injection of gas storage

Abstract

The invention relates to the technical field of oil and gas field development, in particular to a gas storage strong production and strong injection well unblocking and augmented injection method which comprises the nine steps of unblocking liquid preparation, unblocking liquid injection, liquid nitrogen pump injection, shaft gas injection and the like. According to the invention, hydrochloric acid, hydrofluoric acid and fluoboric acid are used as a main body acid system for a plug removal liquid system, and liquid nitrogen is used for replacing a displacing liquid for conventional acidification plug removal operation; after plug removal preparation work is ready, starting an acidification pump truck, sequentially injecting prepared plug removal liquid and active water spacer fluid into a shaft, switching liquid nitrogen to a pump injection process, starting a liquid nitrogen truck set, pumping liquid nitrogen with the volume twice that of the shaft, and squeezing the plug removal liquid and the active water spacer fluid into a stratum. The plugging removal liquid used in the method has high pertinence, liquid nitrogen with good expansion performance is used as displacement liquid, so that the corrosion dispersion performance is good, the use amount of acid liquid is reduced, accordingly, water-sensitive and water-blocking damage of the plugging removal liquid to stratums is reduced, the operation time efficiency is improved, and economical efficiency is considered.

Description

Technical Field

[0001] This invention relates to the field of oil and gas field development technology, and is a method for unblocking and increasing injection in gas storage wells with strong production and injection capabilities. Background Technology

[0002] With the rapid development of my country's economy and the optimization of its energy structure, the construction of gas storage facilities is generally in a mature stage and is expanding nationwide. However, constrained by various factors such as geological conditions, technological level, and capital investment, my country's underground gas storage industry still faces many challenges, such as insufficient scale of gas storage facilities, uneven distribution, and limited peak-shaving capacity.

[0003] There is a lack of research on unblocking and injection enhancement methods for gas storage wells with strong production and injection. Dong Qiwei, Wang Jiangkuan, et al. studied a composite unblocking agent and unblocking and production method for gas storage wells in their paper "A Composite Unblocking Agent and Unblocking and Production Method for Gas Storage Wells". The composite unblocking agent includes a combination of unblocking acid agent, anodic molybdate corrosion inhibitor and temporary plugging agent.

[0004] Rong Xinming, Li Xiang, et al.'s "A Method for Unblocking and Resuming Production of High-Sulfur Water-Producing Gas Wells" optimizes the amount of liquid used in each part of the unblocking system and uses liquid nitrogen to test for flow, achieving the effect of quickly discharging the fluid that entered the well during the blowout period.

[0005] The paper "Slow-Acting Unblocking Agent and Unblocking Method for Oil Wells" by Liang Zhonghong, Zhang Yao, et al. discloses a slow-acting unblocking agent and unblocking method for oil wells. The slow-acting unblocking agent consists of a pre-fluid, a main fluid, and a post-fluid. Both the pre-fluid and the post-fluid use hydrochloric acid as the main acid component to remove inorganic scale precipitation and dissolve residual reaction. The main fluid uses glacial acetic acid and fluoroboric acid as the main acid components to stabilize reservoir clay minerals, slow down the acid-rock reaction rate, expand the unblocking radius, and increase the unblocking depth.

[0006] my country's gas storage facilities are characterized by strong formation heterogeneity, multiple media, extremely low reservoir pressure, and numerous fracture systems. Reservoir protection technology is particularly crucial for complex gas reservoirs with low porosity, low permeability, low production, and strong heterogeneity. Currently, acidizing and unblocking technologies for gas wells are rarely used. Conventional acidizing and unblocking methods for enhanced production and injection have poor applicability, require large amounts of unblocking fluid, and have relatively long operation cycles. Therefore, this research aims to develop a novel method for unblocking, depressurizing, and increasing injection capacity in enhanced production and injection wells in gas storage facilities. This method effectively removes near-wellbore contamination and blockage in these wells, reduces water sensitivity and gas lock damage, and improves injection capacity. Summary of the Invention

[0007] This invention provides a method for unblocking and increasing injection in gas storage wells with strong production and injection capabilities, which overcomes the shortcomings of the prior art. It can effectively solve the problems of near-wellbore pollution and blockage, water sensitivity and gas lock damage, and long unblocking operation time in the current operation of unblocking in gas storage wells with strong production and injection capabilities.

[0008] One of the technical solutions of this invention is achieved through the following measures: a method for unblocking and increasing injection in a gas storage well with strong production and injection, which is carried out according to the following steps: The first step is to prepare the unblocking solution and activated water; The second step is to prepare for acid deblocking; The third step is to pump in unblocking fluid and active water isolation fluid; The fourth step is to inject liquid nitrogen for displacement; Step 5: The congestion relief operation is complete; The sixth step is to carry out gas injection production.

[0009] The following are further optimizations and / or improvements to one of the above-mentioned technical solutions: In the first step above, the unblocking solution, by mass concentration percentage, includes 10% to 12% hydrochloric acid, 1% to 2% hydrofluoric acid, 2% to 4% fluoroboric acid, 0.5% clay stabilizer, 0.3% drainage aid, 3% corrosion inhibitor, 1% iron stabilizer, and 0.3% water-locking inhibitor.

[0010] The above-mentioned active water components, by mass concentration percentage, include 0.5% clay stabilizer and 0.3% drainage aid.

[0011] The components of the aforementioned clay stabilizer include cationic quaternary ammonium salts, the components of the drainage aid include fluorinated surfactants, the components of the corrosion inhibitor include methanol and quaternary ammonium salts, the components of the iron stabilizer include citric acid, and the components of the water-locking inhibitor include polyoxypropylene glycol.

[0012] The second step above, the acid deblocking preparation process includes: S1, prepare liquid nitrogen, in which liquid nitrogen is used to replace the displacement fluid to squeeze the unblocking fluid into the formation and push it into the wellbore and further. S2, Liquid nitrogen vehicle crew ready; S3, connecting the acidification unit and liquid nitrogen truck to high and low pressure pipelines; S4, the acidification unit uses activated water for venting and pressure testing.

[0013] In step S1 above, the amount of liquid nitrogen prepared is twice the wellbore volume.

[0014] In step S2 above, the preparation of the liquid nitrogen truck unit includes: if there is no packer in the wellbore, the working fluid in the wellbore is replaced by air lift using the liquid nitrogen truck unit; if there is a packer in the wellbore, this step is not performed.

[0015] In the third step above, the specific operation of pumping the unblocking fluid and active water isolation fluid includes: after starting the acidification pump truck, the prepared unblocking fluid and active water isolation fluid are injected in sequence, and then the acidification pump truck is stopped.

[0016] In the fourth step above, the specific operation of liquid nitrogen replacement includes: switching the liquid nitrogen pump injection process, starting the liquid nitrogen truck unit, pumping liquid nitrogen with a volume twice that of the wellbore, and squeezing the unblocking fluid and active water isolation fluid into the formation.

[0017] In the fifth step mentioned above, ending the unblocking operation includes stopping the pump and shutting in the well.

[0018] This invention utilizes a deblocking fluid system based on hydrochloric acid, hydrofluoric acid, and fluoroboric acid, replacing the displacement fluid in conventional acidizing deblocking operations with liquid nitrogen. After the prepared deblocking fluid and active water isolation fluid are sequentially injected into the wellbore via an acidizing pump truck, liquid nitrogen with a volume twice the wellbore volume is pumped in to force the deblocking fluid and active water isolation fluid into the formation. This invention uses a more targeted deblocking fluid, employing liquid nitrogen with good expansion properties as the displacement fluid, requiring less acid, effectively removing contamination and blockages, and exhibiting good dissolving and dispersing properties against drilling mud contamination and working fluid leakage. This significantly reduces the water-sensitive and water-locking damage to the formation caused by the deblocking fluid, improves operational efficiency, and is also economical. Attached Figure Description

[0019] Appendix Figure 1 This is a schematic diagram of the operation process of the gas storage forced production and forced injection well unblocking and injection method of the present invention. Detailed Implementation

[0020] This invention is not limited to the following embodiments, and specific implementation methods can be determined according to the technical solutions and actual conditions of this invention. Unless otherwise specified, all chemical reagents and chemical products mentioned in this invention are well-known and commonly used chemical reagents and chemical products in the prior art; unless otherwise specified, all percentages in this invention are mass percentages; unless otherwise specified, all solutions in this invention are aqueous solutions with water as the solvent, for example, hydrochloric acid solution is an aqueous solution of hydrochloric acid.

[0021] The present invention will be further described below with reference to embodiments: Example 1: A method for unblocking and increasing injection in gas storage wells with strong production and injection, characterized by the following steps: The first step is to prepare the unblocking solution and activated water; The second step is to prepare for acid deblocking; The third step is to pump in unblocking fluid and active water isolation fluid; The fourth step is to inject liquid nitrogen for displacement; Step 5: The congestion relief operation is complete; The sixth step is to carry out gas injection production.

[0022] Example 2: As an optimization of the above example, in the first step, the unblocking solution includes, by mass concentration percentage, 10% to 12% hydrochloric acid, 1% to 2% hydrofluoric acid, 2% to 4% fluoroboric acid, 0.5% clay stabilizer, 0.3% drainage aid, 3% corrosion inhibitor, 1% iron stabilizer, and 0.3% water-locking inhibitor.

[0023] Example 3: The active water component, by mass concentration percentage, includes 0.5% clay stabilizer and 0.3% drainage aid.

[0024] Example 4: The clay stabilizer consists of cationic quaternary ammonium salt, the drainage aid consists of fluorinated surfactant, the corrosion inhibitor consists of methanol and quaternary ammonium salt, the iron stabilizer consists of citric acid, and the water-locking inhibitor consists of polyoxypropylene glycol.

[0025] Example 5: As an optimization of the above examples, the second step, the acid unblocking preparation process includes: S1, prepare liquid nitrogen, in which liquid nitrogen is used to replace the displacement fluid to squeeze the unblocking fluid into the formation and push it into the wellbore and further. S2, Liquid nitrogen vehicle crew ready; S3, connecting the acidification unit and liquid nitrogen truck to high and low pressure pipelines; S4, the acidification unit uses activated water for venting and pressure testing.

[0026] In this invention, hydrofluoric acid and fluoroboric acid primarily dissolve and disperse solid particles in drilling mud (such as bentonite) and the working fluid. Before unblocking operations, the working fluid (operational working fluid) in the wellbore must be emptied in advance; 1 m³ of liquid nitrogen can expand into 600 m³ of gas in the formation, and the acidizing pump truck uses activated water to vent the gas, ensuring that the liquid in the acidizing pipeline is activated water; the volume of the acidizing pipeline must be accurately calculated to minimize the amount of activated water isolation fluid used; the construction process must be continuous to avoid discontinuous construction causing the unblocking fluid to remain in the wellbore for a long time; and pressure changes must be closely monitored.

[0027] Example 6: As an optimization of the above example, in step S1, the amount of liquid nitrogen prepared is twice the wellbore volume.

[0028] Example 7: As an optimization of the above example, in step S2, the preparation of the liquid nitrogen truck group includes: if there is no packer in the wellbore, the working fluid in the wellbore is replaced by the gas lift of the liquid nitrogen truck group; if there is a packer in the wellbore, this step is not performed.

[0029] Example 8: As an optimization of the above example, in the third step, the specific operation of pumping the unblocking fluid and active water isolation fluid includes: after starting the acidification pump truck, the prepared unblocking fluid and active water isolation fluid are squeezed in sequentially, and then the acidification pump truck is stopped.

[0030] Example 9: As an optimization of the above example, in the fourth step, the specific operation of liquid nitrogen replacement includes: switching the liquid nitrogen pump injection process, starting the liquid nitrogen truck group, pumping liquid nitrogen with a volume of 2 times the wellbore, and squeezing the unblocking fluid and active water isolation fluid into the formation.

[0031] Example 10: As an optimization of the above example, in the fifth step, ending the unblocking operation includes stopping the pump and shutting in the well.

[0032] The test results of the unblocking fluid in this invention are shown in Table 1. As can be seen from Table 1, all indicators of the unblocking fluid prepared according to the method of this invention meet the requirements.

[0033] Example 11: Based on the geological engineering design, after developing a de-blocking process plan, the de-blocking and injection enhancement method for the gas storage strong production and strong injection wells of this invention was used to perform de-blocking operations on the newly commissioned well (target layer that has not been operated on) Wenchu ​​XX well: The first step is to prepare 8 m³ of unblocking solution, which consists of 12% hydrochloric acid, 2% hydrofluoric acid, 4% fluoroboric acid, 0.5% clay stabilizer, 0.3% drainage aid, 3% corrosion inhibitor, 1% iron stabilizer, and 0.3% water-locking inhibitor. 5 m³ of activated water is also prepared for later use. The second step is to transport 20m³ of liquid nitrogen and use the liquid nitrogen to displace the working fluid out of the wellbore. The acidizing unit and the liquid nitrogen truck are connected to the high and low pressure pipelines, and activated water is used to purge and pressure test the acidizing unit. The third step is to start the acidizing pump truck, inject 8m³ of unblocking fluid and 1m³ of active water into the wellbore, and then stop the pump. The fourth step is to switch to the liquid nitrogen pumping process, start the liquid nitrogen truck, pump 15m³ of liquid nitrogen, and squeeze the unblocking fluid and active water isolation fluid into the formation. Fifth step: When the pump pressure reaches 0 MPa, stop the pump, shut in the well, and the unblocking operation is complete; The sixth step is to perform gas injection production, with a gas injection pressure drop of 8 MPa.

[0034] Example 12: Based on the geological engineering design, after developing a de-blocking process plan, the de-blocking and injection enhancement method for the gas storage strong production and strong injection wells of the present invention was used to perform de-blocking operations on the old well (target layer that has been operated on) Wenchu ​​XX well: The first step is to prepare 5m³ of unblocking solution, which consists of 12% hydrochloric acid, 2% hydrofluoric acid, 4% fluoroboric acid, 0.5% clay stabilizer, 0.3% drainage aid, 3% corrosion inhibitor, 1% iron stabilizer, and 0.3% water-locking inhibitor. 5m³ of activated water is also prepared for later use. The second step involves transporting 20m³ of liquid nitrogen to prepare for acidizing and unblocking. The liquid nitrogen truck will empty the wellbore and use liquid nitrogen to displace the working fluid out of the wellbore. The acidizing unit and the liquid nitrogen truck will be connected to the high and low pressure pipelines. The acidizing unit will use activated water to drain and pressure test. The third step is to start the acidizing pump truck, inject 5m³ of unblocking fluid and 1m³ of active water into the wellbore, and then stop the pump. The fourth step is to switch to the liquid nitrogen pumping process, start the liquid nitrogen truck, pump 15m³ of liquid nitrogen, and squeeze the unblocking fluid and active water isolation fluid into the formation. Fifth step: When the pump pressure reaches 4MPa, stop the pump, shut in the well, and the unblocking operation is complete; The sixth step is to perform gas injection, with a pressure drop of 7 MPa.

[0035] The wellbore unblocking and injection results obtained in Examples 11 and 12 were analyzed and compared with those of conventional acidizing unblocking operations. The results are shown in Table 2. As can be seen from Table 2, in this invention, the amount of unblocking fluid used is reduced by 1 / 2 to 1 / 3 compared with conventional acidizing systems, the cost of the unblocking fluid system is reduced by more than 1 / 2, and the unblocking operation cycle is shortened by 4 to 6 days compared with conventional acidizing unblocking operations. The amount of unblocking fluid used is less, the unblocking work efficiency is higher, and the gas injection capacity is significantly improved.

[0036] Unless otherwise specified, all equipment and apparatus used in this invention are existing, publicly known, and commonly used equipment and apparatus in the field.

[0037] In summary, this method for unblocking and enhancing injection in gas storage wells involving forced production includes six steps: preparing the unblocking fluid and active water, preparing for acidizing and unblocking, pumping the unblocking fluid, and injecting the active water isolation fluid. This invention uses an unblocking fluid system with hydrochloric acid, hydrofluoric acid, and fluoroboric acid as the main acid system, and uses liquid nitrogen instead of the displacement fluid in conventional acidizing and unblocking operations. The unblocking fluid used in this invention is highly targeted, and the displacement fluid uses liquid nitrogen with good expansion properties, resulting in better dissolution and dispersion performance, reducing the amount of acid used, thereby reducing the damage of the unblocking fluid to the formation's water-sensitive and water-locked formations, improving operational efficiency, and also taking into account economic efficiency.

[0038] The above technical features constitute the embodiments of the present invention, which have strong adaptability and implementation effect. Unnecessary technical features can be added or removed according to actual needs to meet the needs of different situations.

Claims

1. A method for plugging removal and injection increase of a gas storage strong extraction and strong injection well, characterized in that The following steps are taken: First, prepare the plug-removing liquid and active water; Second, prepare for acidizing and plug removal; Third, pump the plug-removing liquid and active water isolation liquid; Fourth, inject liquid nitrogen for displacement; Fifth, end the plug-removing operation; Sixth, carry out gas injection for production.

2. The method according to claim 1, characterized in that In the first step, the plug-removing liquid includes 10-12% hydrochloric acid, 1-2% hydrofluoric acid, 2-4% fluoroboric acid, 0.5% clay stabilizer, 0.3% cleanup agent, 3% corrosion inhibitor, 1% iron stabilizer, and 0.3% water lock inhibitor, all by mass percentage.

3. The method according to claim 1 or 2, characterized in that The active water includes 0.5% clay stabilizer and 0.3% cleanup agent, both by mass percentage.

4. The method according to claim 1 or 2 or 3, characterized in that The clay stabilizer includes cationic quaternary ammonium salt, the cleanup agent includes fluorine-containing surfactant, the corrosion inhibitor includes methanol and quaternary ammonium salt, the iron stabilizer includes citric acid, and the water lock inhibitor includes polyoxypropylene glycol.

5. The method according to any one of claims 1 to 4, wherein In the second step, the acidizing and plug-removing preparation process includes: S1, prepare liquid nitrogen, which is used to replace the displacement liquid to push the plug-removing liquid into the formation, the wellbore, and further; S2, prepare the liquid nitrogen truck; S3, connect the high and low pressure pipelines of the acidizing unit and the liquid nitrogen truck; S4, use the active water to empty and test the pressure of the acidizing unit.

6. The method according to claim 5, characterized in that In step S1, the prepared amount of liquid nitrogen is 2 times the volume of the wellbore.

7. The method according to claim 5 or 6, characterized in that In step S2, the liquid nitrogen truck preparation includes: if there is no packer in the wellbore, use the liquid nitrogen truck to pump out the working liquid in the wellbore, if there is a packer in the wellbore, do not perform this step.

8. The method according to claim 5 or 6 or 7, characterized in that In the third step, the specific operation of pumping the plug-removing liquid and active water isolation liquid includes: after the prepared plug-removing liquid and active water isolation liquid are sequentially squeezed into the wellbore, the acidizing pump truck is stopped.

9. The method according to claim 8, characterized in that In the fourth step, the specific operation of injecting liquid nitrogen for displacement includes: switch the liquid nitrogen pumping process, start the liquid nitrogen truck, and pump 2 times the volume of the wellbore to squeeze the plug-removing liquid and active water isolation liquid into the formation.

10. The method according to claim 9, characterized in that In the fifth step, ending the plug-removing operation includes stopping the pump and closing the well.

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