In the Longmaxi shale area in the southwest of Hunan Province, such as shale gas wells like W202 (shale W204H7 - 3), due to complex structures, they are faced with serious casing deformation problems. This problem causes some well sections to be unable to work effectively after the first stage of fracturing, bringing great challenges to shale gas exploitation. In order to deal with this problem, after in-depth research and practice, the temporary plugging fracturing technology combined with core plugging agent and solid limited Communist was adopted, and the original design was changed.
From the perspective of process principle, this technology takes the core plugging agent as the core of the overall plugging technology. Firstly, preliminary construction and verification are carried out. The casing is processed and filled initially, and at the same time, the initial encapsulation treatment is carried out on the remaining well sections from 700m to 24365m, which lays a foundation for the subsequent plugging work. Then, through high-pressure water treatment, the core plugging agent is formed into a composite body composed of airtight core material and high-viscosity solid plugging balls, so as to completely wrap the shale structure to be injected and make the well section reach a closed and stable working state, just like putting a strong "protective clothing" on the well section.
In terms of construction efficiency and cost comparison, for non-deformed wells, the application amount of the core plugging agent is about 2750kg. Although it seems that the cost is high, the construction process of non-deformed well sections is cumbersome and the technical requirements are high.
However, the core plugging agent technology is more economical and effective in this case. It can not only ensure the plugging effect but also reduce construction costs and difficulties. The temporary plugging fluid process takes the core plugging agent as raw material and closes the area to be injected in two stages. In the first stage, the core interlayer is sealed to ensure the tightness of the first-layer plugging; in the second stage, the solid plugging balls are further sealed and mixed evenly to make the plugging effect more stable and reliable.
From the perspective of effect evaluation, after the application of the core plugging agent, the pore occlusion rate reaches 96.13%, which indicates that the flow of gas in the well section is effectively controlled. The gas production volume is basically the same as that of non-deformed wells, ranging from 88% to 92%, which effectively guarantees the surging of shale gas and provides strong support for the stable output of shale gas. Moreover, after replacing the solid limited Communist process with the core plugging agent, the average construction period is shortened by about 36.67% compared with non-deformed wells, which greatly shortens the construction time, lays a good foundation for the subsequent capping construction, improves the construction efficiency and speeds up the development process of shale gas wells.
However, although the core plugging agent technology has achieved remarkable results, there are still some problems to be further explored and solved. For example, some temporary plugging balls have aerosol reaction phenomena, which may affect the stability and durability of the plugging effect. Therefore, it is necessary to use gas leakage and chemical analysis technology to deeply study and correct this problem and provide scientific basis for the improvement of material properties. At the same time, it is also necessary to further improve the core interlayer sealing and solid plugging ball mixing packaging process to ensure the stability of encapsulation effect and the reliability of construction process and continuously optimize the multi-stage encapsulation process. In addition, it is necessary to conduct a comprehensive technical evaluation and economic benefit comparison on the technology and process adopted by the core plugging agent, establish a more perfect evaluation system, and comprehensively consider various factors such as technical parameters, construction costs and economic benefits to determine the most suitable temporary plugging fracturing technology scheme.
Only in this way can we continuously improve various process links in actual construction, deeply study the performance characteristics of plugging balls, and formulate more scientific, reasonable and economic optimization schemes in combination with actual conditions to ensure the long-term stable application of temporary plugging fracturing technology in casing deformed shale gas wells and provide solid technical support for the efficient exploitation of shale gas. In short, the temporary plugging technology of core plugging agent and solid limited Communist shows great potential and advantages in the application of casing deformed shale gas wells.
Through continuous research and improvement, it will surely play a more important role in the field of shale gas exploitation and promote the continuous development of the shale gas industry.