Reservoir Simulation to Diagnose the Causes of Reduced Well Production Efficiency in Coal Bed Methane

Abstract

This paper gives a detailed description of Coalbed Methane reservoirs and also few case studies have been presented. This report is divided into five different parts, starting with the introduction of the Coalbed Methane reservoir and highlighting the physical aspects of the reservoir.  After reviewing five SPE journal papers, a detailed summary of these papers has been presented in this report.A generalized material balanced equation that accounts for and incorporates the Langmuir isotherm, initial free gas, water expansion and formation compaction. This particular form of material balancing can be used to estimate the original gas in place and unlike other methods does not require an iterative process to solve the equations. Also this report documents the practical application of the proposed material balanced equation. This paper also shares case histories and best practices developed from designing and placing the cement successfully in Coalbed methane wells in India. These case histories include cement design considerations and special cement placement techniques.  Reservoir models that incorporate the unique flow and storage characteristics of CBM reservoirs have been developed to study the production and decline characteristics of the reservoir.Further production facilities described include artificial lift, wellhead separation, gathering systems, compression, gas treating and water disposal. Finally we conclude the report by use of reservoir simulation to diagnose the causes of reduced well production efficiency.

Keywords: MBE, CBM, Porosity, Coal, Design system.