Research on CBM drilling technique for U-shaped horizontal well connected remotely with directional well

To solve the problems of the imperfect technology of remote connection between coalbed methane (CBM) U-shaped horizontal well with directional well, the difficulty during butting construction, the collapse of caves in coal seam and so on, new drilling technology is explored. Key technologies,such as mosaic temporary plugging drilling fluid and geo-steering drilling, combined with new cave shielding technology which uses outer pipe to shield the cave and operates in inner pipe, were adopted in the drilling of P15 test wells. It shows that the adopted series of technologies can ensure the remote connection, provided that the shielding in cave is set up in advance. In P15 test wells, the horizontal drilling footage of 724 m was completed among which 668 m are in coal seam. So, the drilling rate of coal seam is 92.3%. In addition, the horizontal well was connected successfully at 1 242.5 m on the first try. At the same time, the cave shielding creates a new passage for sand fishing and the later drainage, and the problem of cave collapse in CBM wells can be solved. The present research improves the technology of connecting CBM horizontal well with directional well, and provides a new way for development of CBM with low cost and high benefit.