The production economics of tight to near-tight formations such as the Clinton sands of Ohio have become increasingly marginal due to rapidly increasing well costs and geologically less favorable areas to drill. To evaluate the potential for improved well performance, the Gas Research Institute (GRI) sponsored the empirical investigation of historical Clinton sand well performance presented herein.

The study is based on well data from 303 wells in northeastern Ohio which were drilled between 1963 and 1974. All the wells were single-completions stimulated by hydraulic fracturing for which at least five years of uninterrupted production data are available. The data are believed to be representative of Clinton wells in the 1963 to 1974 time frame and were selected only on account of availability. Statistical regression methods were used to determine well parameters which impact individual well performance. The five-year cumulative production (first five years) for each of the 303 wells was used as the dependent variable in a multivariable linear regression equation, with the statistically significant well parameters as independent variables.

The empirical regression equation was used to estimate average well performance (five-year cumulative production) for geographically oriented subsets of the 303-well data base with varied levels of stimulation treatment volume. Significant variations in well performance are demonstrated as a function of apparent geologic variations and variations in stimulation treatment volume. Historical production (303 wells) could have been increased by 15 percent through use of near-optimum stimulation treatment volumes. A method is proposed which utilizes the statistical regression methods of the study, in conjunction with exploratory drilling in areas which are geologically similar to those represented by the data base, to assist in optimizing future Clinton sand production.

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