Recent measurements of methane emissions from abandoned oil/gas wells show that these wells can be a substantial source of methane to the atmosphere, particularly from a small proportion of high-emitting wells. However, identifying high emitters remains a challenge. We couple 163 well measurements of methane flow rates; ethane, propane, andn-butane concentrations; isotopes of methane; and noble gas concentrations from 88 wells in Pennsylvania with synthesized data from historical documents, field investigations, and state databases. Using our databases, we (i) improve estimates of the number of abandoned wells in Pennsylvania; (ii) characterize key attributes that accompany high emitters, including depth, type, plugging status, and coal area designation; and (iii) estimate attribute-specific and overall methane emissions from abandoned wells. High emitters are best predicted as unplugged gas wells and plugged/vented gas wells in coal areas and appear to be unrelated to the presence of underground natural gas storage areas or unconventional oil/gas production. Repeat measurements over 2 years show that flow rates of high emitters are sustained through time. Our attribute-based methane emission data and our comprehensive estimate of 470,000–750,000 abandoned wells in Pennsylvania result in estimated state-wide emissions of 0.04–0.07 Mt (1012g) CH4per year. This estimate represents 5–8% of annual anthropogenic methane emissions in Pennsylvania. Our methodology combining new field measurements with data mining of previously unavailable well attributes and numbers of wells can be used to improve methane emission estimates and prioritize cost-effective mitigation strategies for Pennsylvania and beyond.

Abandoned oil and gas (AOG) wells can provide pathways for subsurface fluid migration, which can lead to groundwater contamination and gas emissions to the atmosphere. Little is known about the millions of AOG wells in the U.S. and abroad. Recently, we acquired data on methane emissions from 42 plugged and unplugged AOG wells in five different counties across western Pennsylvania. We used historical documents to estimate well depths and used these depths with the emissions data to estimate the wells' effective permeabilities, which capture the combined effects of all leakage pathways within and around the wellbores. We find effective permeabilities to range from 10(-6) to 10(2) millidarcies, which are within the range of previous estimates. The effective permeability data presented here provide perspective on older AOG wells and are valuable when considering the leakage potential of AOG wells in a wide range of applications, including geologic storage of carbon dioxide, natural gas storage, and oil and gas development.

Historically the mining industry has not viewed methane as a resou'rce. The existence. of methane in an underground mine presents a great hazard as mixtures of methane and air are combustible over a wide range of concentrations. Methane has contributed to a large number of serious accidents. To reduce the hazard methane presents, the mining industry has developed systems to remove methane gas from the mine.At this time the only method being employed at the Left Fork Mine to remove methane is the mine ventilation system. Data for the methane content of the ventilation air at the Left Fork Mine, as analyzed by the Department of Labor, was obtained. Consistently, the methane content was measured at one one-hundredth of a percent. We are not aware of any economically viable processes that can effectively recover this small fraction of methane.To prevent this methane from being vented to the atmosphere, degasification wells are proposed. These wells could be drilled into the coal seam prior to the coal being mined. Over a five year period these wells could recover approximately 22% of the methane that exists in the coal. This methane would be of sufficient quality to be used in normal applications or sold to a pipeline.Solutions Engineering, working with information presented by the Bureau of Mines, the United States Geological Survey, the Department of Energy and the Left Fork Mine estimated the methane gas reserves that exist in the mine. This estimate is based on current mine expansion plans. Using this information and a three dimensional dual porosity --single permeability simulator, forecasts of methane production rates for various degasification well arrangements were made. This information indicated that The environmental impacts and benefits of using this technology are summarized in the report. The study indicates the methane emission reduction that could be achieved on a National and Global level. The important point being that this technology is economically viable as is demonstrated in the report.Phase I of this project, the feasibility study, was completed in 60 days. Phase II which will perform the engineering required to install a fuel cell at the mine will be completed over the next twelve months. Phase II will address issues such as which methane source is the most practical, where to locate the fuel cell and how the electrical energy can best be utilized.