Evaluation of Fracturing Methods for the Stimulation of Devonian Shale in Northern Ohio. Final Report

摘要

A comparison of core analyses from Lorain and Trumbull Counties with those from gas producing areas showed that the shale sections in both areas contain adequate matrix gas for commercial production. Although we observed large natural gas shows in Lorain County and measured high concentrations of matrix off-gas in the core from both project areas, no significant gas production resulted from 15 individual stimulations in the Devonian shale sections of 10 wells in Trumbull and Lorain Counties, Ohio. These results indicate that hydraulic fracturing treatments using a foam medium (as performed under this contract) were unsuccessful in achieving commercial production in either area. We obtained similarly unproductive results using a CO sub 2 -water medium for fracturing in Lorain County. Two operational failures prevented our obtaining a valid test of the displaced explosive fracturing concept. These negative experiences could result from a combination of: (1) failure to effectively contact the target horizons with the stimulations, (2) formation damage due to the completion operations, and (3) a limited extent of natural permeability planes, but not from the level of matrix gas concentrations in the treated formations. Core samples from both counties gave little evidence of natural fracture development. Permeable zones within silty horizons may control the location of the local gas shows. Further shale research in northern Ohio should first focus on actual producing areas, and attempt to delineate the permeability trends. Future tests of stimulation methods should include borehole shooting. Although shooting may not induce extensive fractures, it should ensure at least some contact with nearly all of the treated section. In so doing, it may serve as a reasonable basis of comparison with other treatment techniques. (ERA citation 07:052728)