Evaluation of bedding effect on the bursting liability of coal and coal-rock combination under different bedding dip angles

Abstract

Heat injection is essential for oil shale in-situ conversion technology. The downhole of the heat injection well reaches temperatures above 400 • C during the process of heat injection, and part of the high-temperature gas dissipates through the wellbore annulus. Consequently, in addition to causing energy loss, the dissipation causes thermal damage to the casing and wellhead. To avoid dissipation, components that are suitable for high-temperature environments should be sealed and used during heat injection while mining. Therefore, this study presents the design of a packer composed of elastic graphite rubber and a high-temperature-resistant material. The influence of numerous factors, such as downhole temperature, working load, and height of rubber, on the reliability of the packer was analyzed. Subsequently, the numerical simulation analysis of the packer reliability in insitu conversion mining under high temperature and pressure environments was performed. The results indicate that when the operating temperature is stable, the operating load has the most obvious influence on the sealing reliability of the packer, whereas the change in the height of the rubber has the least significant effect on the maximum contact stress between the casing and rubber. The change in the operating temperature has the least significant effect on the overall sealing performance of the packer. Moreover, the rise of the temperature will increase the sealing reliability of the packer, and on the contrary, the drop in the temperature will decrease it.

Research on the deformation mechanism and ACC control technology of gob‐side roadway in an extra‐thick coal seam with varying thickness

“…The above control methods have all achieved good support effects in their respective projects, but the support is still mainly axial control, with insufficient consideration given to tangential control of the support structure. During the process of deformation and failure of the surrounding rock, lateral displacement and shear expansion of the surrounding rock are very common phenomena, 32,33 resulting in frequent breakage of anchor bolts and cables. Therefore, the research team has invented a new type of support structure called “Anchor Cable with C‐shaped Tube (ACC)”, which not only ensures the high axial bearing capacity of the support components, but also significantly improves the tangential bearing capacity 34–36 .…”