Well Spacing Effects on Well Productivity in Coalbed Methane Reservoirs

Abstract

Indonesia has large coalbed methane (CBM) reserves (453 TCF) and has the potential
to supply domestic natural gas. One of the problems in producing gas from CBM is the
amount of time that the dewatering process takes. The dewatering process involves
draining water to reduce the pressure so that the methane gas can come out (as in Field
X, Kalimantan). To accelerate the dewatering process, a well spacing method is used to
determine the number of wells that will affect the cumulative gas production. A greater
number of wells will increase CBM gas production but will also increase the cost and
duration of production, so an economic analysis is needed to provide limits and determine
the optimum yield. This paper will be conducted with a numerical simulator to discern the
effects of well spacing on well productivity in CBM reservoirs. The result shows that
models with 160 acres of well spacing have a recovery factor of 16,07%, 320 acres have
a recovery factor of 11,5%, and 640 acres have a recovery factor of 5,82%. The result
suggests that narrow spacing of wells causes greater cumulative gas production, but it
plateaus (stabilizes) more quickly