INTRODUCTION

Coalbed methane reservoirs are relatively new production opportunities, and much of the current knowledge and expertise has been pioneered by Amoco. Previously, methane has been produced from coalbeds by injecting water to create a pressure gradient across the reservoir. As water flows from an injection to a producing well, it desorbs methane gas from coal pore surfaces. The liberated methane flows along coal cleats, into coal fracture systems, and along to the producing wells. Recently, new production technology has been tested by injecting nitrogen to lower the partial pressure of coalbed methane. The liberated methane is driven below the bubble point, and is more efficiently produced as a liquid hydrocarbon rather than a gas.

The success of coalbed-methane production depends critically on understanding the in situ spatial properties of coal, the reservoir coal fracture systems, the macro flow patterns and permeabilities of the reservoir, and the ability to detect and monitor the spatial distribution of injected and produced gas. Amoco have donated data to my thesis project on the basis that they hope 3-D seismic impedance estimates may help clarify the spatial heterogeneity and production rates of their coalbed reservoirs.

In the remainder of this brief paper, I discuss my research goals for the data set, show some examples from the 3-D $\grave{P}\!\acute{P}$ land data, and point out some interesting features, problems and prospects in the data with respect to my inversion goals.