Water-energy nexus : case study Marcellus Shale gas play

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Petrou, Zacharias

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The Marcellus Shale is the largest shale gas play in the U.S., accounting for a total amount of around 65 Tcf of gas reserves. Its development was made possible by hydraulic fracturing (HF) and horizontal drilling. HF however demands large volumes of water to produce gas. Water is an important resource and the purpose of this work was to investigate the relationship between water consumption and natural gas production. The results of this study should inform policy-makers and stakeholders about the importance of water for natural gas supply from the play. The study is based on historical data from 5769 horizontal gas wells that were completed in the period 2008-2013. The main focus was on water and proppant used to complete wells over time. I analyzed the variability in completion practices in conjunction with the production variability, which among other things are related to natural gas market prices, geology and technology. Statistical analysis leads us to conclusions that simple metrics, such as averages or medians could be misleading when applied to aggregated data. I expanded the statistical analysis by using more advanced approaches, e.g. boxplots, applied to disaggregated data. I found that trends cannot be easily observed in the completion and production data, owing to a variety of spill-over effects from external changes in economic and technical variables. This made it necessary to perform a more granular analysis. Namely, I disaggregated the data by year on a regional and company levels. As a result, I was able to show that though the conceptual framework is valid, the relationship between completion inputs (water, sand, lateral length, and unobservable technological and physical properties) is not linear and may change over time. Among the examined ratios were: HF water use per foot of lateral, proppant loading per gallon of water and proppant use per foot of lateral. The expected ultimate recovery (EUR) was examined on a per well basis, per gallon of HF water use, per gallon of water use per foot and per pound of proppant per foot. The study concluded that further investigation is required with non-linearity effects taken into account. Market prices of natural gas, geological characteristics of the location of a well and technological differences greatly affect the amounts of water used for gas production purposes as well as the EUR



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