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Copyright of Coal Geology & Exploration is the property of Xian Research Institute of China Coal Research Institute and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In order to overcome the downhole high temperature problem during the drilling process of long horizontal section in deep Marine carbonate formation, a transient numerical model of wellbore temperature distribution during drilling process was established, and multi-source terms, non-Newtonian fluid helical flow and variations of thermophysical properties in combination with the characteristics of long horizontal section drilling in deep Marine carbonate gas reservoir were considered. Based on the model, the effects of horizontal section length, circulation time, drilling fluid displacement, and inlet temperature on the wellbore temperature distribution during horizontal well drilling were studied. The results show that the bottom-hole temperature will increase significantly with the increase of horizontal section length; measures such as increasing circulation time, increasing circulation displacement and lowering drilling fluid inlet temperature have little effect on decreasing bottom-hole temperature in deep long horizontal sections. It can be seen that in order to ensure the smooth development of deep carbonate oil and gas resources, the temperature tolerance limit of rotary steerable tools should be increased. [ABSTRACT FROM AUTHOR]

Ground grouting technology is effective method to prevent and control coal mine water hazard, and grouting multi-branch horizontal well is the foundation of ground grouting technology. Combined the characteristics of geological conditions, drilling techniques and grouting techniques, the truck-mounted drilling rig, rare-earth permanent magnet direct drive mud pump, EMWD and solid control system were selected, which were suitable for grouting well. The key technologies such as drilling structure, trajectory control, casing construction were studied. A set of drilling equipment and key technologies for grouting multi-branches horizontal well was formed, it had great significance to prevent and control water hazard in coal mines.

In view of the problems that tap fishing is not easy to make buckles, and sleeve milling fishing in the fishing of deep hole, complex track hole and down hole cannot stick the broken drill pipe in the hole, etc., two kinds of claw-clamping type fishing bits are designed. In this paper, the structure and characteristics of claw-clamping type fishing bit are introduced, claw-clamping type fishing process is described in detail, and the conditions of the claw-clamping type fishing bit to clamp the drill pipe are given.

Copyright of Coal Science & Technology (0253-2336) is the property of Coal Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)