Best Pumping Practices to Optimize Dewatering in CBM wells: Lessons Learned Developing Raniganj East Field, India

Abstract

Abstract Dewatering is required to remove water from the coal seams so that bottomhole pressure (BHP) is reduced to a critical point where gas will begin to desorb from the coal. Production Data analysis of over 100 wells which includes both vertical and deviated in Raniganj East Coalbed Methane (CBM) field, India indicates that wells were not dewatered continuously. This was mainly due to the fact that the wells go on workover and extended periods of pump downtime result in re-saturation of the cleat and fracture system with water, thereby inhibiting gas production. So starting and stopping pumping resets the hydrostatic back pressure and water saturation profiles to initial conditions in the reservoir while the gas content remains unchanged, thereby requiring more pumping to achieve the previous level of gas production. An attempt was made to analyze the problem and through production surveillance of past four years production history, various reasons why continuous dewatering was not achieved were pump failures due to high torque, low torque, low pump efficiency and erratic loading conditions. The causes of these pump failures were gas locking, rod/tubing unscrew, stator damage, hole in tubing, plugged intake screens and insufficient motor cooling, etc. This paper discusses best practices to dewater CBM well after rich experience gained by operator in CBM Raniganj East field from series of trial of artificial lift ESP and PCP pump run in individual wells with design modification by using tailpipes and provides specific recommendations and pump operating parameters to dewater effectively and continuously from both vertical and deviated well.