The Permeability Factor in Coalbed Methane Well Completions and Production

Abstract After 30 years of CBM production in the USA, and internationally more recently, general principles and decision trees have emerged to guide an operator in choosing a well completion based on permeability. If enough permeability measurements are made, well completions can be prioritized, and hybrid well completions evaluated. The benefits of horizontal and multilateral wells are made clear. Low permeability is a serious challenge for CBM ventures, and further success will entail finding regions of enhanced permeability, utilizing horizontal wells, and "creating" permeability by new-paradigm methods. Perm-based guidelines for CBM well completions are given, which include permeability bands and benchmarks. Industry success has led to two benchmarks for evaluating ahead of full-field development (1) commercial success from reservoir parameters, and (2) effectiveness of well completions. The perm-based guidelines are simple and practical, and should benefit any CBM completions strategy. We also re-examine the striking observations of permeability increases with depletion (10-100 times) in the San Juan basin. The latest attempts to model and match the strong permeability increases with depletion in the San Juan basin are evaluated. Although there remain differences, a consensus has been obtained for some reservoir parameters.