Anaysis of Production and Reservoir Characteristics from the Drunkards Wash Coalbed Gas Field, Utah; Identification of Parameters Favoring High-Performance Gas Wells

Naranjo, John C.¹, David E. Tabet^2 
1 University of Utah, Salt Lake City, UT
² Utah Geological Survey, Salt Lake City, UT

Drunkards Wash field is Utah’s largest coalbed gas field, and the field has grown since its discovery in 1992 to become the largest producing gas field in the state. Parts of the field now have a mature production history of covering at least 10 years, allowing analysis of well production characteristics to help determine key parameters that might identify high-performance well locations in the greater Ferron coalbed gas fairway. Decline curve analysis was used to determine months to peak production, peak production of gas and water, estimated ultimate recoverable gas reserves, and well life for the study wells. The average exponential decline rate after peak production is achieved was found to be 18 percent, the average well life will be 17 years, and the average estimated ultimate recoverable gas reserve is estimated to be 1.9 billion cubic feet, on a per well basis. Wells with high water production tend to have correspondingly high gas production. Additional factors such as net coal thickness, average coalbed thickness, number of coalbeds, and depth to the coalbed reservoirs were compiled and analyzed; higher average coalbed thickness shows a weak correlation to higher ultimate recoverable reserves. In addition to tabular and graphical study of these parameters and their interrelationships, a number of these factors were mapped to examine their spatial distribution in Drunkards Wash field.