During the past five years, nearly 10,000 Antrim Shale, Devonian Shale and eastern coalbed methane wells have been drilled and completed in eastern basins. A portion of these new wells (and previously drilled, older wells) appear to have been inefficiently completed, stimulated and produced, due to limited understanding of the production mechanisms and lack of sound data on the interaction of drilling fluids on the shale or coal reservoir. Thus, substantial improvements may be achieved by remediating these wells. The economic incentives for remediation are particularly powerful. Successful remediation not only provides additional low cost gas production but may also provide additional Section 29 tax credits.
In the Antrim Shale, remediation involving pump refracturing and completion of additional zones have led to substantial gains in gas production. However, the identification of wells requiring restimulation has been more challenging. Pressure buildup testing and productivity index matching have been utilized to identify such candidates.
In the Warrior Basin, restimulation of poorly producing wells has had more mixed results. Based on the experiences learned from the GRI Rock Creek Field Laboratory, a remediation program is being initiated in the Warrior Basin with support of GRI and basin operators.
This paper sets forth a technical and economic rationale for a remediation research and deployment program for eastern gas shale and coalbed methane wells. A series of case studies summarize some of the results achieved to date.
Large numbers of wells have been drilled in eastern basins for recovering natural gas from coalbeds and organically rich shales. A recent tabulation shows that nearly 35,000 such wells exist, with over 10,000 such wells drilled in the recent years. These wells include 4,000 Michigan Basin Antrim Shale wells, about 4,000 Warrior Basin and other eastern coal basin wells, and 27,000 Appalachian Basin Devonian age shale wells.
A "first order" appraisal of these coal and shale wells indicates that a substantial portion of these wells could benefit from remediation.