During the fracking process, highly pressurized mixture of water and proppants (sand and chemicals) is injected into to a crack, which fractures the surrounding rock structure and proppants help in keeping the fracture open. Over a longer period, however, these fractures tend to close due to the difference between the compressive stress exerted by the reservoir on the fracture and the fluid pressure inside the fracture. During production, fluid pressure inside the fracture is reduced further which can accelerate the closure of a fracture.
In this thesis, we study the stress distribution around a hydraulic fracture caused by fluid production. It is shown that fluid flow can induce a very high hoop stress near the fracture tip. As the pressure gradient increases stress concentration increases. If a fracture is very thin, the flow induced stress along the fracture decreases, but the stress concentration at the fracture tip increases and become unbounded for an infinitely thin fracture.
The result from the present study can be used for studying the fracture closure problem, and ultimately this in turn can lead to the development of better proppants so that prolific well production can be sustained for a long period of time.
Natural gas development in the Northern Appalachian region has skyrocketed dramatically over the past decade. Correspondingly to the unprecedented growth rate of the natural gas industry, population health risks have shifted dramatically in response to both aerial and water pollution. With energy as a key input in all sectors of Appalachian life, the Pennsylvania region serves as a fascinating case study where clusters of unconventional gas drilling wells intersect varying population densities and governing laws to create different levels of health risks. Studies have found that horizontal hydraulic fracking corresponds to an increased risk of upper respiratory symptoms (URS), low birth weights, premature births, and certain cancers (White et al., 2009). Also, zoning and local planning laws are policy tools local governments can use to directly influence community wellbeing (Diez-Roux, 2011). This study will focus on the spatial relationship between upper respiratory symptoms (URS), a key volatile health benchmark, and the zoning/planning laws that the Oil and Natural Gas Industry must adhere to. Our project seeks to provide a preliminary understanding of the interplay between different natural gas zoning laws and the resulting health implication risks that appear in the Marcellus shale region of Pennsylvania. This is necessary to appropriately regulate and monitor hydraulic fracking. To get a better understanding of this phenomenon, spatial autocorrelation and analysis of variance statistics are integrated to generate a surface-level understanding of areas impacted by natural gas development. To guide the creation of our models, we geographically process the unconventional well locations, upper respiratory symptom health utilization, and zoning law data to develop insights that policymakers can take into consideration. Regionally, natural gas has become an integrated part of the energy sector and a driver of local economic development. The patterns drawn from this assessment provide a novel way of understanding the population health risks posed by different zoning ordinance models.
