Selection of Best Drilling, Completion and Stimulation Practices, Coalbed Methane Reservoirs
Sunil Ramaswamy, Walter Ayers, and Stephen Holditch
Petroleum Engineering, Texas A&M University, College Station, TX
Expansion of the coalbed methane (CBM) industry over the past three decades led to diverse drilling, completion and stimulation practices to address complex geologic settings and reservoir parameters encountered. For example, openhole cavity completions are highly successful in the CBM “fairway” of the San Juan basin, whereas, in other parts of that basin, hydraulic fracturing of single or multiple coal zones is the most common completion/stimulation method. In other basins, newer technology includes single horizontal and pinnate drilling patterns. The objectives of this study were to (1) determine which geologic parameters affect CBM drilling, completion and stimulation decisions, (2) identify to the engineering best practices for specific geologic settings, and (3) present these findings in advisory charts.
To determine CBM best drilling, completion and stimulation practices, we reviewed literature and solicited industry experts’ opinions using a questionnaire. Thirteen geologic parameters that commonly are assessed when selecting CBM engineering practices are coal thickness, number of seams, areal extent, dip, depth, rank, gas content, formation pressure, permeability, water saturation, and compressive strength, as well as the vertical distribution of coal beds and distance from coal beds to fracture barriers or aquifers.
We identified the optimum CBM drilling, completion and stimulation practices for specific geologic settings (combinations of the 13 parameters) and captured the results in two advisory charts that may be used to select best drilling and completion practices and the optimum stimulation fluids. The advisory charts are presented in a Visual Basic for Applications software program to facilitate their use. The engineering best practices identified in this project may be applied to new or existing fields, to optimize gas recovery and project economics.
AAPG Search and Discover Article #90078©2008 AAPG Annual Convention, San Antonio, Texas