Abstract: Distribution and Development of Natural Gas Within Big Injun and Weir Reservoirs of West Virginia
David L. Matchen, Ana G. Vargo, Ronald R. McDowell
West Virginia lies in the center of the Applachian basin and has been producing natural gas since the late 1800s. Peak production of gas for West Virginia is reported to have occurred in 1917 at approximately 308,620 MMcf. Historically, the Mississippian Big Injun and Weir reservoirs have been important gas producers. Pre-1900 drilling was concentrated in the northern part of the state and primarily exploited the Big Injun sandstone. In 1894, Moses Spencer No. 1 (Tyler County) struck gas in the Big Injun sandstone and reportedly produced 50 to 100 MMcf of gas daily. Development quickly spread southward through the state following structural trends. Today, the Big Injun and Weir reservoirs produce gas from 150 of the 377 named oil and gas fields in West Virginia.
The reservoirs can be separated into two plays: (1) Big Injun, and (2) Weir. Big Injun reservoirs include sandy units of the basal Greenbrier Limestone and the Big Injun and Squaw sandstones of the Price Formation. Weir reservoirs are comprised of sandstones situated between the bottom of the Big Injun sand and the top of the Sunbury Shale. Commonly, this interval consists of interbedded sandstones, siltstones, and shales. Locally, however, productive sandstones of the Weir interval can reach a composite or individual thickness greater than 100 feet.
The Big Injun is the more widespread and prolific of these two plays. As the Big Injun is composed of several different stratigraphic units, the thickness of this reservoir varies greatly and can exceed 100 feet locally. This situation prevails to the north, where thick sections of Price Sandstone come into contact with basal units of the Greenbrier Limestone. In central West Virginia, the upper units of the Price Formation have been removed by pre-Greenbrier erosion restricting production to the porous basal Greenbrier. In regions where the basal Greenbrier is tight, production comes solely from the Price Formation.
The Weir is more localized, lies approximately 100 to 250 feet below the Big Injun and, thus, is only rarely affected by the erosion surfaces that often truncate the Big Injun. The Weir was originally identified in a southern trend (Kanawha County) during the early 1900s. The productive Weir reservoir occurs in a north-south trend of thick (>75 ft) sandstones. Development of this productive trend continued for several decades and was eventually extended further south. More recently (1950s and 1960s), a northern trend with similar reservoir characteristics was developed in Ritchie and Doddridge counties.
Different stratigraphic and structural features control the geographic distribution of the two plays. The combination of gently folded structures and erosion surfaces results in a large variety of Big Injun fields. Thickness and porosity variations control hydrocarbons within the Weir play, which lies in at least two distinct north-south trends within the state.
AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994