STUDY SEEKS TO BOOST APPALACHIAN GAS RECOVERY

Ashland Exploration Inc. and the Gas Research Institute (GRI) are trying to find ways to increase gas recovery in the Appalachian basin.

They are working together to investigate Mississippian Berea sandstone and Devonian shale in a program designed to achieve better understanding and improved performance of tight natural gas formations in the area.

"The joint project gives us the opportunity to receive specific information and evaluate results and tests on wells that never would have been tested or reviewed in depth because of economic constraints," said J.T. Mellinger, Ashland Exploration vice-president and manager of the company's eastern region.

WHAT'S BEING DONE

Three wells on Ashland Exploration acreage in Pike County, Ky., are involved in the research program.

Findings from the first two wells will be used to optimize evaluation and completion of the third well. The first two wells have been drilled. Drilling of the third well was under way at last report.

Ashland Exploration has been involved with GRI's Devonian shale research since 1988.

GRI's initial focus was on well stimulation because Devonian shale wells it reviewed had much lower recoveries than could be expected, based on estimated gas in place. Research during the past few years was designed to improve the execution and quality control of well stimulation.

Mellinger said, "The focus of current research is to more closely examine the reservoir to determine whether we should deal with the Devonian shale as numerous small reservoirs instead of one large one. This could lead to a procedure that would result in several small fracture treatments instead of the current program of one or two large treatments per well."

Mellinger also said GRI has recovered the first known air cut Devonian shale core and has conducted the first open hole permeability tests with gas instead of fluid.

"This is significant in that coring time is reduced," he said. "Many believe fluids normally used for coring and testing result in formation damage, which affects results."

LACK OF DATA

David Hill, GRI project manager for Devonian shale research called the performance of natural gas wells in the Devonian shale and Berea sandstone of the Appalachian basin "unpredictable and often disappointing."

The low permeability formations hold total gas in place of about 5.5 bcf/sq mile, of which GRI estimates 50-60% is recoverable during 30-50 years.

"Typically," Hill said, "very little data are collected to accurately describe these reservoirs. Hence, no one really knows how these wells ought to perform."