Natural Gas Production in Virginia: Devonian and Mississippian Conventional Reservoirs, but Mainly Pennsylvanian Coalbed Methane

My Own Adventures with Drilling in Virginia

     Back around 2004 or 2005, I was mapping and working onsite at wells in Southwestern Virginia. We had a farmout of conventional well acreage amidst a coalbed methane (CBM) field. A different company owned the CBM rights and freely exercised its right to deny well locations that we chose. They had wanted the conventional acreage but did not want to develop it as fast, so there was significant tension around that. Our main drilling target on our acreage in Buchanan County was the Berea Sandstone. We also produced from the Devonian Gordon zone and the Mississippian Weir formation, both of which are rather tight sandy siltstones. We also knew that we were drilling near and within a producing channel in the Upper Mississippian Ravencliff Sandstone, an incised valley fill sandstone with scouring at the base and braided streams with pebbles (which I saw when we cored it in Southern West Virginia) and coarse sandstone. We knew about Ashland Oil Company’s old Ravencliff wells in the area with high IPs up to 30MMCF/day that produced well for a few years, then dropped off considerably. These wells were shallow at around 1200 ft deep.

     At the end of one day in the office, we got a call that we hit a large amount of gas in the Ravencliff, measured via u-tube at 29MMCF/day, and we would have to kill the well with a pump truck. I would have to make the 3.5-hour trip for the geophysical logging job. The well ended up producing quite well for about 6 months, but dropped off pretty fast.  

     We also had a well down there with a difficult location on top of a narrow mountain. There was one way up and one way down along a corkscrewed road with switchbacks. When they were getting ready to frack the Berea well with nitrogen, the nitrogen truck slipped off the road and rolled sideways down the hill a couple of hundred feet. Luckily, the driver was not hurt, but some of the liquid nitrogen leaked out of the truck and froze some of the surrounding vegetation.

     At the time, I was also following the drilling adventures by a Michigan-based company, Dart Energy, in Tazewell County to the south. These wells were finding gas in faulted and fractured zones in different Mississippian formations. It was part of what we called the Alleghenian Thrust Play, where the tectonic stresses were such that gas migrated along open fractures created by the thrusting. I studied well logs looking for thickened sections and repeated sections indicative of low-angle thrust faults. Certain formations seemed to be more susceptible to fracturing and hosting gas, even at low porosity. One zone of interest was the Mississippian Pocono formation, which was a siltstone with an average of 4-5% density porosity on logs. I was able to attend a field trip with the Appalachian Geological Society, where we looked at an outcrop of the Pocono Formation down in Mercer County, West Virginia. This was a very interesting outcrop that was folded to the point that the rocks were mostly upside down, and we were looking directly at the face of the rocks. One could see the basic fracture spacing of about 4-6 inches by the gridded weathering on the rocks. One could also see the folding in individual rocks, which came off in plates about a half-inch thick. I also noticed that the rocks were iron-stained and made a metallic sound when struck. The rock was known to grade into a red siltstone of the Borden formation in Kentucky. In any case, I believe the Dart wells also found some gas in the Pocono. I believe some of their tests were rank wildcats in the far eastern part of Tazewell County. I did not have access to any of their logs, only hearsay from a land person.  We drilled some wells in the formation in Raleigh County, West Virginia, and Cabot Oil & Gas had drilled some large wells in the formation in Wyoming County, West Virginia. These were big gas producers. 

     At the 2004 Eastern Section AAPG meeting, I attended a fracturing workshop that detailed the characteristics of fracturing in both compressional and extensional tectonic regimes. I learned about type II and type III fractures associated with anticlines and found the information useful for determining ideal well location candidates.

     Our biggest Pocono well in Raleigh County was the biggest well in the company division, producing steadily at 3MMCF per day for at least the first three months. It had an IP of 9MMCF/day. There is likely more potential for these thrust plays in both Southern West Virginia and Southwestern Virginia. The thrust play was also produced from the Gordon, Berea, Weir, and Big Lime formations. We ran seismic to confirm the geological interpretations and got a fair correlation between log-derived geology and seismic geology. 

     Around 2000 conventional wells have been drilled in Virginia. I was able to work directly on about 20 of those wells, about 1% of them. It was a beautiful area to visit, with some interesting plant life.

     The bigger natural gas story in Southwest Virginia is coalbed methane from the Norton, Lee (New River), and Pocahontas Formations. These wells are produced mainly from the Nora Field and other fields in Buchanon, Dickinson, and Wise Counties. The CBM wells have long been produced as horizontal wells, which enhances their production rates. These are “gassy” coals and are economical when gas prices are high. The coal beds are typically drilled before mining to de-gas the mines. 

     The coal mines near and in the Nora Field are also the site of greenhouse gas mitigation efforts by CNX to convert vented methane to flares, which significantly reduces greenhouse gas accumulation. The Mountain Valley Pipeline developers agreed to do this as a way to offset the emissions of their project, though I am unsure of the current status. I was also familiar with drilling Pocahontas Formation CBM wells in Southern West Virginia, having worked on several well tests, early horizontal well tests, and some coring of the formation.  

     As the graph below shows, both conventional gas and CBM peaked in 2011 at around 150BCF and have been declining since then. The latest figures from 2024 show statewide production just below 80 BCF. CBM typically produces 75-80% or more of the state’s gas.

 

     There is also potential for gas production in the Devonian Lower Huron Shale, which produces some gas in the area, but much more in nearby Eastern Kentucky. Below is a log cross-section of the Lower Huron zone.

    

References:

 

Natural Gas. Virginia Department of Energy. Virginia Energy - Geology and Mineral Resources - Natural Gas

Devonian Shale Gas. Virginia Department of Energy. Virginia Energy - Geology and Mineral Resources - Devonian Shale Gas