While the Central Appalachian region is known for such hydrocarbon resources as coal, it also hosts unconventional gas resources, such as coalbed methane, shale gas, and other tight gas formations. Many of these gas resources, at depths of up to 15,000 feet, are vertically stacked so that a single well or group of wells could produce simultaneously from multiple reservoirs. While many of the shallower reservoirs produce at relatively low production rates, the deeper formations, referred to as emerging plays, remain largely untested.
A group of academic and industry experts, including the Virginia Center for Coal and Energy Research (VCCER), EnerVest Operating LLC, and researchers at Virginia Tech believe that these emerging plays offer the potential for increased hydrocarbon resources for the state and nation, and that their development could provide a critical economic transformation to a region transitioning from coal mining.
In a collaborative effort with funding from the Department of Energy’s National Energy Technology Laboratory, researchers from VCCER and Virginia Tech are leading a field laboratory that will begin drilling a 15,000-foot characterization well to explore and investigate the potential for multiplay production of emerging unconventional reservoirs in Central Appalachia.
The Emerging Stacked Unconventional Plays project is led by Nino Ripepi, an associate professor of mining and minerals engineering in the College of Engineering, and is a continuation of work started in April 2018 with more than $8 million in DOE support. Since the project’s start, Ripepi and the research team from VCCER and Virginia Tech have sited, designed, permitted, and set surface casing on a 15,000-foot characterization well to explore the potential of deep unconventional resources.
The group has positioned a triple stand drilling rig at a field site in Wise County, Virginia, to drill to a planned depth of 15,500 feet. Well logging, coring, and core analyses will focus on the Deep Conasauga-Rome Petroleum System, which includes the formation known as the Rogersville shale, as well as any formations of interest discovered during drilling.
“This work offers a chance to identify and evaluate the resource potential of multiple reservoirs in the area, which in turn can lead to further natural gas development and job growth in a region of the country hard-hit by the downturn in coal,” Ripepi said.
Analysis and modeling for enhanced understanding of energy resources
A primary objective of the project is obtaining data needed to better understand the energy resources and their potential development. Core analysis and reservoir modeling are essential to evaluating the production potential of unconventional gas resources, said Ripepi.
“The analysis of rock cores at VCCER and Virginia Tech laboratories, coupled with information gained from state-of-the-art well logs, will provide inputs for reservoir modeling activities,” Ripepi said. “Modeling can more accurately simulate hydrocarbon production, and the resulting predictive simulations will help researchers develop strategies that can produce hydrocarbons economically from these deep reservoirs.”
Researchers will analyze rock cores acquired from the deep drilling activities in labs on campus by examining permeability, fracture conductivity, and adsorption, and by conducting geochemistry experiments to identify parameters to input into predictive reservoir models.
A multidisciplinary endeavor
The Emerging Stacked Unconventional Plays research team is multidisciplinary, with expertise in core analysis, imaging techniques, and fluid flow modeling. Ripepi serves as the project’s principal investigator and is joined by Michael Karmis, the Stonie Barker Professor and director of VCCER; mining and minerals engineering assistant professors Cheng Chen, Ellen Gilliland, and Bahareh Nojabaei; geosciences associate professor Ben Gill; and Virginia Tech research associates Charles Scholsser and Cigdem Keles.
The research team also includes industry and research experts James Ayers, Trevor Schaffer, and Kevin Miller of EnerVest Operating LLC; Robert Vagnetti of the National Energy Technology Laboratory; and consultants Jerry Hill and Jack Pashin.
Ripepi believes that an unprecedented amount of recoverable hydrocarbons are available from unconventional resources due to recent advancements in deep horizontal drilling technology coupled with reservoir stimulation advancements. Ripepi explained, however, that uncertainty about deep hydrocarbon resources and effectiveness of novel completion technologies in the more accessible Lower Huron shale often deter the level of investment required to develop Central Appalachia’s deeper natural gas-bearing reservoirs.
A deep exploratory well, such as the one undertaken by the field laboratory, is unique in that it can target the Rogersville shale — the source rock for other more shallow gas reservoirs located in the Floyd Embayment, which extends from eastern Kentucky into Wise and Dickenson counties in Virginia. “This will be the first deep exploration well into the Floyd Embayment in Virginia and will help in understanding the deep subsurface,” said Ripepi.
Social license: The environment and communities
While the Emerging Stacked Unconventional Plays project team believes the resource’s potential for development is an important goal, they also seek to understand how to better navigate exploration and potential development of the emerging plays with minimal environmental impact and maximum socioeconomic benefits.
The field site location in Wise County, Virginia, is home to pristine temperate forests and freshwater streams. The collaborators said the project places a strong emphasis on environmental protection in the context of natural resource development.
“If deep hydrocarbon resources are discovered, it is prudent to develop them in a sustainable way where economic, environmental, and social factors of the community are all considered,” said Ripepi.
One way this may be done, said Ripepi, is by encouraging active stakeholder engagement from the community, coupled with technologies that reduce surface and infrastructure requirements. “The advent of horizontal drilling technologies has allowed for a significantly reduced surface footprint while still improving the economic recovery of hydrocarbon reserves.”
“While many in our community and world are navigating uncertain times, this research project provides an opportunity to take a step away from that world and study rocks that were created hundreds of millions of years ago,” said Ripepi. “It is exciting to be at the forefront of exploring the geologic unknown in a search for hydrocarbon resources that are critical to the future of the economy and future generations.”
– Angelo Biviano