An excellent flushing efficiency evaluation device is indispensable for studying the cementing flushing fluid. However, the existing flushing efficiency evaluation device cannot simulate the formation and flushing process of the downhole mud cake. Therefore, this paper proposes a novel flushing efficiency evaluation device that can simulate the formation and flushing of downhole mud cakes. The rotational speed of the device during flushing and the rotor’s diameter is deduced based on the principle of equal wall shear rate. The evaluation device and method can be used to quantitatively evaluate the flushing efficiency of the flushing liquid on the mud cake under high temperatures and high pressures. This device analyzed the effects of the annular gap, temperature, construction displacement, and flushing fluids on flushing efficiency. The results show that the smaller the annular gap, the higher the temperature, the larger the displacement, the higher the scouring efficiency, and the higher the shear bond strength. Fiber flushing has the dual function of mechanical and chemical flushing, so its flushing efficiency is 14.75% higher than that of heavy flushing fluid at 10 min. The surfactant in the emulsified rinse leads to a sudden increase in rinse efficiency in the middle and late stages. The reduced flushing efficiency of the flushing fluid is due to the reduced ζ potential.
Casing deformation caused by fault and fracture sliding derived from fracturing has attracted growing attention. Casing deformation frequently occurs during the hydraulic fracturing process in the Sichuan Basin. Although its mechanism has been intensively studied, this issue is becoming increasingly severe and demands immediate solutions, especially in the shale gas blocks of Changning-Weiyuan-Zhaotong. The present study summarizes and analyzes the research progress relevant to casing deformation based on the existing literature. It is shown that the casing deformation rate of the deflection point on the shale gas horizontal well is much higher than that of other places and that shear deformation is the dominant form. The main factors influencing the casing deformation of shale gas horizontal wells include weakened strength of the collapsing casing, geological factors, cement, cement quality sheath, fracturing engineering factor, etc. We propose to reduce casing deformation by optimizing well trajectory, improving casing strength and cementing quality or optimizing fracturing operation. In addition, a hierarchical relationship between the influencing factors is also provided. However, the mechanisms of some forms of casing deformation need to be further studied, and the casing deformation in shale gas exploitation must be solved urgently.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.