Carbon dioxide blocking remover microbubble system energizing and blocking removal process

Abstract

The invention relates to the technical field of condensate gas reservoir unblocking processes, in particular to a carbon dioxide unblocking agent microbubble system energizing and unblocking process which comprises the following steps: step 1, a unblocking pipe string with a plurality of micropores communicated inside and outside in the outer side of the lower part is lowered to a target position in a shaft; and 2, setting an annular space between the lower end of the plug removal pipe string and the shaft. The advantages of foam profile control and energy increasing and plug removal of the plug remover and CO2 are combined, and the size of microbubbles can be controlled by changing the pore diameter of micropores according to the size of formation pores. And meanwhile, a stable bubble source can be provided for underground microbubbles by adjusting the gas-liquid ratio. The blocking remover is injected into the stratum in the form of microbubbles, so that the blocking removal effect can be enhanced, the deep profile control effect on the stratum can be achieved, the swept area of the blocking remover is increased, the problems of non-uniform blocking removal and incomplete blocking removal in the prior art are solved, the use cost of the liquid-phase blocking remover can be effectively reduced, and the application prospect is wide. And carbon sequestration can be realized by injecting CO2 microbubbles at the bottom of the well.

Description

Technical Field

[0001] The invention relates to the technical field of condensate gas reservoir unblocking technology, in particular to a carbon dioxide unblocking agent microbubble system energy-enhanced unblocking technology. Background Art

[0002] During the development of condensate gas reservoirs, due to the gradual depletion of formation pressure, a large amount of condensate oil will be precipitated near the production wells, forming a condensate oil pollution zone, causing "oil blockage" and reducing the gas well production. And when there is bottom water or edge water near the condensate gas reservoir, water invasion and water channeling will occur during the development of the gas reservoir, causing gas well flooding and "water blockage". In severe cases, the gas well will completely stop production. "Oil blockage" and "water blockage" are objective factors that reduce the production of condensate gas reservoirs. Therefore, in response to the above problems, the development of unblocking technology is of great significance for extending the development life of gas fields, improving the recovery rate of condensate oil and gas, and ensuring energy security.

[0003] At present, the common method of injecting fluid into the formation is to remove the condensate oil and water flooding pollution in gas wells. Common methods of unblocking include injection of foaming agent, injection of plugging agent (intermediate phase, methanol), gas injection (nitrogen, CO2), and energy-enhanced unblocking (CO2+unblocking agent segment plug). Among them, injection of foaming agent can only remove the accumulated liquid in the wellbore, and it is difficult to be effective for deep formation pollution; injection of plugging agent can reduce the capillary pressure of oil-water and gas-water interfaces, and reduce the seepage resistance of gas, but the unblocking agent requires additional energy for backflow, and it is difficult to use in formations with insufficient energy; gas injection can penetrate the contaminated zone, form a new seepage channel, and can increase the formation pressure, replenish the formation energy, and facilitate backflow, but in the case of severe heterogeneity of gas reservoir permeability, it is difficult to inject the injected gas into the formation evenly, and the unblocking effect is not good.

[0004] Defects of the prior art: At present, the main methods for unblocking condensate gas reservoirs include injection of foaming agent, injection of plugging agent, gas injection (dry gas, natural gas, CO2), injection of methanol, gas injection huff and puff, methanol slugging, and CO2-unblocking agent slugging. The invention patent with application number CN200410081127.7 discloses a method for removing the pollution of retrograde condensate near the well by gas injection through huff and puff of condensate wells. This method is for condensate gas wells that are determined to be blocked by retrograde condensate through dynamic analysis. After shutting down the well to clear the collected liquid in the well cavity, the production well is transformed into a gas injection well, and natural gas that has been deoiled, dehydrated and treated with impurities is injected into the well. After the injected gas volume is consistent with the simulated calculated injection volume, the well is shut down, and the change of wellhead pressure is observed. When it is close to the shut-in pressure before gas injection, it means that the injected gas has diffused to the distant formation, and then the well is opened for production. This method can only remove the retrograde condensate pollution in the near-well area, and has poor effect on removing the pollution caused by water channeling and water invasion. The invention patent with application number CN201510394345.4 discloses a method for preventing and removing water lock and anti-condensation agents in condensate gas wells and a method for preparing and using the agent. The method first uses a plug injection method to inject a plugging remover into the formation, then backflows, and then uses a plug injection method to inject a synergist solvent and a double-repellent treatment agent solvent into the formation, thereby preventing and removing water lock and anti-condensation damage. Although this method can remove the pollution of the two reservoirs, in the face of heterogeneous formations, the injected fluid will enter along the high permeability channel, thereby greatly reducing the blocking effect. Therefore, it is urgent to develop a condensate gas reservoir blocking process that can be applied to heterogeneous formations and can remove multiple pollution factors to solve the problems existing in the prior art, which is of great significance and practical value to achieve the improvement of oil and gas recovery in condensate gas reservoirs. Summary of the invention

[0005] The present invention provides a carbon dioxide plugging remover microbubble system energy-enhanced plugging remover process, which overcomes the shortcomings of the above-mentioned prior art and can effectively solve the problem that when facing heterogeneous formations, the injected fluid will penetrate along the high permeability channel, thereby greatly reducing the plugging remover effect.

[0006] The technical solution of the present invention is achieved by the following measures: A carbon dioxide blockage remover microbubble system energy-enhancing blockage removal process, comprising the following steps:

[0007] Step 1: lower a plugging-removing pipe string having a plurality of micro-holes connected inside and outside on the lower outer side into a target position in the wellbore;

[0008] Step 2: Setting and unblocking the annulus between the lower end of the pipe string and the wellbore;

[0009] Step 3, injecting a plugging remover into the annulus through the wellhead;

[0010] Step 4: Inject CO2 gas into the inner side of the upper end of the unblocking pipe string. The CO2 gas mixes with the unblocking agent through the micropores and enters the formation and is buried.

[0011] The following are further optimizations and / or improvements to the above technical solutions:

[0012] The above CO2 storage rate can be calculated by the following formula:

[0013]

[0014] in, is the mass of CO2 produced in the form of free gas, is the mass of CO2 in the plugging remover, is the CO2 quality in the produced condensate oil, is the total mass of CO2 injected into the core.

[0015] The unblocking pipe string in the above step 1 may include an air injection pipe, a filter pipe and a packer fixed together in sequence from top to bottom, and micropores are arranged on the wall of the filter pipe.

[0016] The filter tube may be a metal powder sintered filter element with a tubular structure, and the diameter of the micropores on the outer side of the filter tube is not greater than 50 microns.

[0017] The gas injection pipe may be made of stainless steel. A support pipe is fixedly installed between the lower end of the gas injection pipe and the upper end of the packer. The upper and lower ends of the support pipe are respectively sealed and fixedly installed with the upper and lower ends of the filter pipe. A plurality of connecting holes that connect the inside and the outside are discretely distributed on the outside of the support pipe corresponding to the position of the filter pipe.

[0018] The present invention combines the advantages of foam profile control, unblocking agent and CO2 energy unblocking, and can control the size of microbubbles by changing the micropore diameter according to the pore size of the formation. At the same time, a stable bubble source can be provided for the microbubbles downhole by adjusting the gas-liquid ratio. The present invention injects the unblocking agent into the formation in the form of microbubbles, which can not only enhance the unblocking effect, but also play a role in deep profile control in the formation, increase the affected area of ​​the unblocking agent, and not only solve the problems of uneven unblocking and incomplete unblocking in the past, but also can effectively reduce the use cost of the liquid phase unblocking agent, and can achieve carbon sequestration by injecting CO2 microbubbles at the bottom of the well. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Attached Figure 1 It is a schematic diagram of the main view and partial cross-section structure of the unblocking pipe string in Example 1.

[0020] Attached Figure 2 Schematic diagram of the CO2 plugging remover microbubble system in Example 1.

[0021] The codes in the attached drawings are: 1 is the gas injection pipe, 2 is the filter pipe, 3 is the packer, 4 is the support pipe, 5 is the connecting hole, and 6 is the wellbore. DETAILED DESCRIPTION

[0022] The present invention is not limited by the following embodiments, and specific implementation methods can be determined based on the technical solution of the present invention and actual conditions.

[0023] In the present invention, for the convenience of description, the relative position relationship of each component is described according to the attached Figure 1 The positional relationships such as front, back, top, bottom, left, and right are described according to the layout directions of the drawings in the specification.

[0024] The present invention will be further described below in conjunction with embodiments and drawings:

[0025] Embodiment 1: As shown in the attached Figure 1 , 2 As shown, the carbon dioxide plugging remover microbubble system energy-enhancing plugging remover process includes the following steps:

[0026] Step 1: lower a string of unblocking pipes with a plurality of micro-holes connected inside and outside on the lower outer side into a target position in the wellbore 6;

[0027] Step 2: Setting and unblocking the annulus between the lower end of the pipe string and the wellbore 6;

[0028] Step 3, injecting a plugging remover into the annulus through the wellhead;

[0029] Step 4: Inject CO2 gas into the inner side of the upper end of the unblocking pipe string. The CO2 gas mixes with the unblocking agent through the micropores and enters the formation and is buried.

[0030] Before the unblocking operation is carried out, the required microbubble size and the gas-liquid ratio of the injected medium are determined through indoor experiments. A gas-liquid ratio of 1:1 is usually selected. Condensate gas reservoir pollution may include pollution factors such as gas lock, retrograde condensation pollution, scale pollution, and water-sensitive pollution. Before using this method, the pollution factors of the target reservoir should be understood in advance, and the unblocking agent should be configured according to the corresponding pollution conditions to improve the unblocking efficiency. In order to stabilize the generated microbubbles, a surfactant is added to the unblocking agent. If the unblocking agent formula contains a surfactant, or there is more water in the unblocking agent, the unblocking agent is directly injected.

[0031] First, lower the unblocking pipe string with multiple micropores connected inside and outside the lower outer side into the target position in the wellbore 6, then seal the annulus between the lower end of the unblocking pipe string and the wellbore 6, start injecting unblocking agent into the wellbore 6 and the annulus of the unblocking pipe string, and finally inject CO2 into the unblocking pipe string. After passing through the micropores at the bottom of the unblocking pipe string, CO2 is divided into smaller CO2 gas masses. After the CO2 gas masses enter the unblocking agent, they form nano-micron-level microbubbles with the unblocking agent. As more and more microbubbles are generated, the pressure in the annulus rises, and the microbubbles enter the formation. When the microbubbles enter the formation, they will preferentially enter the large pores. After being squeezed in the large pores, the microbubbles will block the large pores, so that the subsequent microbubbles can enter the relatively small pores, and so on, and finally the microbubbles carrying CO2 and unblocking agent are evenly distributed in the target formation. When the microbubbles encounter formation water and condensate, they will break, and the plugging remover and CO2 will act on the nearby formations, condensate, and formation water, and then remove the plugging, which can improve the efficiency of plugging removal. After injecting CO2, close the wellhead, wait for a period of time, and then open the wellhead to discharge the fluid in the annulus.

[0032] Injecting the plugging remover into the formation in the form of microbubbles can not only enhance the plugging removal effect, but also play a role in depth profile adjustment in the formation, increase the affected area of ​​the plugging remover, and realize CO2 storage. When CO2 is incorporated into the condensate oil, the volume of the condensate oil expands, reducing the viscosity of the condensate oil and improving the fluidity of the condensate oil. When CO2 combines with water, the carbonic acid produced can dissolve the cement in the rock, improve the permeability of the formation, and remove the retrograde condensation pollution of the formation. The CO2 plugging remover microbubble system can have the advantages of both CO2 and plugging remover. The structure of the microbubble can block the high permeability channel, so that the plugging removal system can be evenly injected into the formation. There is more gas and less liquid in the CO2 microbubble, and the amount of plugging remover entering the formation is relatively small. This can not only reduce costs, but also reduce reservoir damage, and at the same time, CO2 can be stored to achieve the goal of carbon neutrality.

[0033] CO2 has the characteristics of good injectability, can expand condensate oil, reduce condensate oil viscosity, and extract light components in condensate oil. It can extract condensate oil and remove "oil blockage". At the same time, CO2 will undergo phase change and volume expansion during the backflow process, which can promote the discharge of water in the formation. The unblocking agent can change the wettability of the reservoir and reduce the capillary force of the reservoir. A good unblocking agent has weak adsorption in the reservoir, can achieve deep unblocking, and can effectively remove "water blockage". Dispersing CO2 in the unblocking agent in the form of microbubbles can effectively avoid the occurrence of tongue-in and finger-in, realize the uniform injection of the unblocking system in the unblocking well, and improve the unblocking efficiency.

[0034] According to actual needs, the above-mentioned carbon dioxide plugging remover microbubble system energy-enhancing plugging removal process can be further optimized and / or improved:

[0035] Example 2: As an optimization of the above example, the CO2 storage rate is calculated by the following formula:

[0036]

[0037] in, is the mass of CO2 produced in the form of free gas, is the mass of CO2 in the plugging remover, is the CO2 quality in the produced condensate oil, is the total mass of CO2 injected into the core.

[0038] This allows the amount of CO2 stored in the deplugging process to be calculated when the well is subsequently opened.

[0039] Embodiment 3: As an optimization of the above embodiment, as shown in the attached Figure 1 As shown, the unblocking pipe string in step one includes an injection pipe 1, a filter pipe 2 and a packer 3 fixed together from top to bottom, and micropores are provided on the wall of the filter pipe 2. By providing the packer 3, fixed-point unblocking can be achieved. The unblocking agent is injected from the annulus between the wellbore 6 and the unblocking pipe string, and the packer 3 blocks the unblocking agent to prevent it from penetrating into the formation below and causing pollution. During foaming, the continuous CO2 will be divided into nano-micron-level bubbles after passing through the micropores and enter the unblocking agent, forming an unblocking agent-CO2 microbubble system.

[0040] Embodiment 4: As an optimization of the above embodiment, as shown in the attached Figure 1 As shown, the filter tube 2 is a metal powder sintered filter element with a tubular structure, and the diameter of the micropores on the outside of the filter tube 2 is not greater than 50 microns. When in use, the size of the microbubbles can be controlled by changing the micropore diameter according to the size of the formation pores. The micropore diameter can be 5 microns to 15 microns. At the same time, a stable bubble source can be provided for the microbubbles downhole by adjusting the gas-liquid ratio. It can effectively reduce the use cost of the liquid phase plugging remover, and carbon sequestration can be achieved by injecting CO2 microbubbles downhole.

[0041] Embodiment 5: As an optimization of the above embodiment, as shown in the attached Figure 1 As shown, the gas injection pipe 1 is made of stainless steel, and a support pipe 4 is fixedly installed between the lower end of the gas injection pipe 1 and the upper end of the sealer 3. The upper and lower ends of the support pipe 4 are respectively sealed and fixedly installed with the upper and lower ends of the filter tube 2. A plurality of connecting holes 5 that connect the inside and the outside are discretely distributed on the outside of the support pipe 4 corresponding to the position of the filter tube 2.

[0042] According to the needs, the upper end of the support tube 4 and the upper end of the filter tube 2, as well as the lower end of the support tube 4 and the lower end of the filter tube 2 are fixed together by a number of corrosion-resistant stainless steel bolts evenly spaced along the circumference, and the ends of the bolts are screwed into the wall of the support tube 4. This can prevent CO2 gas from directly entering the deblocking agent from the connection gap between the bolts and the support tube 4, thereby reducing the formation efficiency of microbubbles.

[0043] The above technical features constitute the embodiments of the present invention, which have strong adaptability and implementation effect. Non-essential technical features can be added or reduced according to actual needs to meet the requirements of different situations.

Claims

1. A carbon dioxide plugging remover microbubble system energy-enhancing plugging removal process, characterized in that The steps include: Step 1: lower a plugging-removing pipe string having a plurality of micro-holes connected inside and outside on the lower outer side into a target position in the wellbore; Step 2: Setting and unblocking the annulus between the lower end of the pipe string and the wellbore; Step 3, injecting a plugging remover into the annulus through the wellhead; Step 4: Inject CO2 gas into the inner side of the upper end of the unblocking pipe string. The CO2 gas mixes with the unblocking agent through the micropores and enters the formation and is buried.

2. The carbon dioxide plugging remover microbubble system energy-enhancing plugging remover process according to claim 1, characterized in that The CO2 storage rate is calculated by the following formula: in, is the mass of CO2 produced in the form of free gas, is the mass of CO2 in the plugging remover, is the CO2 quality in the produced condensate oil, is the total mass of CO2 injected into the core.

3. The carbon dioxide blocking agent microbubble system energy-enhancing blocking removal process according to claim 1 or 2, characterized in that The unblocking pipe string in step 1 includes an air injection pipe, a filter pipe and a packer fixed together in sequence from top to bottom, and micropores are arranged on the wall of the filter pipe.

4. The carbon dioxide blocking agent microbubble system energy-enhancing blocking removal process according to claim 3 is characterized in that The filter tube is a metal powder sintered filter element with a tubular structure, and the diameter of the micropores on the outside of the filter tube is not greater than 50 microns.

5. The carbon dioxide blocking agent microbubble system energy-enhancing blocking removal process according to claim 3 is characterized in that The gas injection pipe is made of stainless steel. A support pipe is fixedly installed between the lower end of the gas injection pipe and the upper end of the packer. The upper and lower ends of the support pipe are sealed and fixedly installed with the upper and lower ends of the filter pipe respectively. There are several communicating holes connecting the inside and the outside of the support pipe corresponding to the position of the filter pipe.

6. The carbon dioxide blocking agent microbubble system energy-enhancing blocking removal process according to claim 4 is characterized in that The gas injection pipe is made of stainless steel. A support pipe is fixedly installed between the lower end of the gas injection pipe and the upper end of the packer. The upper and lower ends of the support pipe are sealed and fixedly installed with the upper and lower ends of the filter pipe respectively. There are several communicating holes connecting the inside and the outside of the support pipe corresponding to the position of the filter pipe.

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