Drilling Techniques in J-Shaped Extended Reach Horizontal Wells in Shallow Coal Bed Methane Reservoirs in the Zhijin Block

The drilling phase for in the Zhijin coalbed methane (CBM) block is characterized by a low drilling rate for the coal seam, a difficult-to-protect reservoir, high cost of drilling horizontal connected wells, and a low economic benefit. In order to solve these problems, the technical difficulties of J-shaped horizontal drilling were applied to this block and analyzed. Then, drilling techniques in such wells drilling in shallow CMB reservoirs were studied from well track optimization, casing program optimization and borehole trajectory control. Finally, the process underwent a practical test in the Zhiping 1 Well. This well was drilled smoothly with horizontal lateral of 500.00 m, horizontal displacement 818.98 m, maximum deviation angle 97.6°, drilled coal seams 293.00 m and coal seam drilling rate 58.6%, which is much higher than that of horizontal connected wells (43.6%). In addition, the cost to drill the well was only 58% of that of U-shaped horizontal connected wells. The positive results indicated that these drilling techniques in J-shaped horizontal well could be successfully implemented in drilling wells in the Zhijin Block.