Optimizing Stimulation of Coalbed Methane Reservoirs Using an Integrated Fracture Modeling Approach

Abstract

Abstract Conventional methodologies have failed to address the difficulties involved in the design and execution of fracture treatments of reservoirs with complex geology and stress conditions such as coal bed methane (CBM) reservoirs. This paper presents an innovative technique to optimize and design hydraulic fracture treatments in naturally fractured CBM reservoirs. This methodology integrates (1) a three dimensional (3D), finite element based numerical design tool to predict the fracture geometry for given reservoir and operating conditions, (2) a production model to estimate fluid flow in the CBM reservoir, and (3) cost analysis to optimize the design parameters against different field scenarios using a hybrid genetic-evolutionary optimization tool. The technique has been used to design fracture treatments in a coal bed methane reservoir to illustrate its potential benefits in improving the reservoir's productivity. Results of this study have shown that the use of a 3D geometry model enabled realistic post-frac productivity analysis. This provided reliable conservative estimates on the revenue derived from the stimulation program. Furthermore, the optimization approach allowed operators to incorporate operating constraints based on sound industry practice and company guidelines for a cost-effective exploitation of CBM reservoirs.