A Preliminary Geology-Based Natural Gas Resource Assessment of the Marcellus Shale for West Virginia

Pool, Susan; Boswell, Ray; Lewis, Eric; Mathews, Jonathan P.

This study examines how much natural gas is likely to be contained in the Marcellus Shale underlying West Virginia, its distribution, and the geographic variability of key parameters affecting gas recoverability. Approaches to estimating natural gas resource volumes can be divided, in general, into two categories for continuous unconventional reservoirs--1) those that use production data to estimate recoverable resources directly and 2) those that use geologic data to estimate original gas-in-place to which recovery factors can be applied. The production approach is based on past well performances which may be unrepresentative of future productivity, particularly when an unconventional play is in the early stage of development. Therefore to conduct a more comprehensive and flexible examination of State resources, this study applies the geologic approach for resource quantification. Original gas-in-place is determined using well logs and core data; recovery factors are calculated by comparing the gas-in-place estimates to production data. Well log data from more than 300 wells scattered across the State and core data from at least one well are being used to investigate the geology while production data from more than 400 non-commingled wells, also scattered across the State, are being used to establish recovery factors. Geological interpretation software is used to perform log analysis and geographic information system tools are used to manage data, generate volumetric estimates, and convey information.

Results and products of the study include: 1) estimates of total original gas-in-place and potential recoverable volumes; 2) cross-sections highlighting the Marcellus Shale, as well as maps highlighting wells, reservoir location and geographic extent, reservoir thickness, reservoir depth, formation pressure, original gas-in-place volumes, and recoverable gas volumes; and 3) an up-to-date, publicly-accessible, web-based, map application.

The resource assessment can be refined readily as new data are obtained and can be adjusted as technology and economics change. In addition, the approach can be used for other gas plays such as the Utica Shale and can be extended to other geographic areas within the region.

AAPG Search and Discovery Article #90163©2013AAPG 2013 Annual Convention and Exhibition, Pittsburgh, Pennsylvania, May 19-22, 2013