Innovative Field Development Strategy Tackles Complexities of Flue Gas Buildup in Reservoir - LWD and “Distance to Boundary” Technology Comes to Aid

Abstract

Most of the fields in the northern part of Cambay basin are characterized by heavy crude. To enhance productivity, Insitu combustion had been practiced in this belt over a long period of time. The in-place combustion of hydrocarbon also produces residual gases called Flue gas, which in time migrates and accumulates towards structural highs. The buildup of flue gas pockets towards reservoir top slowly began affecting production in this belt with conventional producers showing premature gas cuts. This created the need for an effective change in strategy that would yield gas free production. The following paper illustrates a very challenging field development strategy deployed in field Z, located in this belt to tackle complexities of flue gas build up in reservoir.The strategy firstly involved changing the planned drainhole geometries in field Z from vertical and near vertical to horizontal. Horizontal producers has reduced coning and cusping effect and enhanced sweep radius. The main challenge with this strategy was to place these producers at safe distance from the gas pockets at top. To handle this challenge, LWD and "Distance to Boundary" technology was deployed for the first time in this field.A combination of gamma ray, resistivity and density-neutron data would help to track the flue gas zone while drilling which could be used to land the build section at a safe distance below gas caps. "Distance to Boundary" technology would be used during drainhole to detect the reservoir bottom and keep trajectory at about 2-3m from bottom. Placing drainhole close to reservoir bottom would ensure a safe distance from gas pockets throughout the drilled interval.This strategy worked effectively with 3 wells been drilled till now in field Z with very good production rates without any gas cut.