Analysis and optimization of coalbed methane gas well production

Coalbed methane wells have been used for many years as a viable means of extracting quantities of methane gas for use as a clean and efficient energy source. However, there is a limited understanding of many of the factors involved during the extraction process. As the more easily attainable reservoirs are depleted, it is imperative to gain a greater comprehension of these factors in order to develop techniques to efficiently collect economical quantities of methane gas in the future.

For this investigation, an extensive database was compiled, consisting of a large set of parameters pertaining to the development of coalbed methane gas wells. Using the information contained in this database, a statistical analysis was performed in order to gain a better understanding of the relationships between the many factors involved in extracting quantities of methane gas from the ground. The results of this analysis showed that the majority of the parameters shown to have the greatest impact on methane production were heavily dependent upon the geology of the region. As a result, any attempt to exploit them for optimization exercises would be extremely difficult. Of the parameters shown to have the least dependence on naturally occurring phenomena, the amount of proppant sand used to hold fractures open within the well system after stimulation was shown to have the most impact

During the well stimulation procedure, the proppant sand is carried into the fractures in the strata by a foam fracturing fluid. The sand acts to support the fracture system, increasing the permeability of formation, and allowing the methane gas to flow to the wellbore. By treating the sand particles with certain reagents, it is possible to render them hydrophobic, making it possible for them to stick to the bubbles within the foam and be carried deeper into the formation. Results of an investigation of sands treated to different degrees of hydrophobicity have shown that such treatments significantly increase the amount of sand distributed over a greater distance.