CSG Cleat Compressibility Examples

Introduction

Cleat Compressibility values reported by various workers, shown below, vary by almost an order of magnitude. According to Seidle, controls on coal compressibility are poorly understood, making prediction of this parameter difficult. Coal rank and geologic age appear to minimally affect compressibility, if at all, while the role of other variables such as ash and mineral matter, maceral distribution, and coal lithotypes has not been heavily studied.

For comparison, pore volume compressibility of conventional reservoir rocks range from 10-6 to 10-4 psia-1. Thus, coal cleat compressibility can be 10 to 1,000 times larger than that of conventional reservoirs.

References:

• John Seidle, Fundamentals of Coalbed Methane: Reservoir Engineering, 2011, PennWell Corporation.