Investigating the utilization of surfactant in liquid unloading experiments of a propped fracture

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Mulkay, Connor Dixon

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The United States currently leads global production of oil and gas fundamentally in part due to its successful large shale plays. Advancements in technology and research have allowed the US to apply production techniques that increase recovery from these unconventional reservoirs; one of these principally being fracing. Through fracing, large fractures are created in the highly impermeable rock, thus increasing the amount of surface area for hydrocarbon flow and unlocking profitable production. After these fractures are created, the high amount of production only continues for a relatively short amount of time, after which production steeply slows down. Most companies react to this by drilling and fracing a new well in a different location. If these fractures could be improved so that the reduction in productivity is slowed down, companies would not have to drill as many well thereby saving money and causing less environmental disturbances. An idea to mitigate the productivity decline is by quickly unloading the built-up liquid in a newly created fracture. If suspended in a fluid for a period of time, gravitational forces cause proppant to settle in the lower part of the fracture. As the liquid slowly seeps into the formation, closure stresses from the surrounding rock begin to exceed pressure in the fracture and the upper part of the fracture closes off due to a lack of proppant. The surface area of the fracture promoting hydrocarbon flow is then drastically reduced. The closed off fracture could also potentially close off routes of flow if it is a critical pathway. A hypothesis is that if the built-up fluid in the fracture is unloaded quickly, the fracture will have a more homogenous distribution and will promote better fluid flow, thus slowing down the productivity decrease that is normally observed. Surfactants are already used for a variety of applications in the oil and gas industry. This thesis involves conducting experiments using surfactants to remove the built-up fluid in a fracture. Investigations are performed with different combinations of fluids typically used in industry. A fracture model made out of plastic plates is filled with proppant and a test fluid, and air is injected at the bottom of the fracture. The volume of liquid that exits the fracture is recorded as time passes. Results show that surfactant significantly improves the volume of unloaded liquid, even when in contact with oil at So = 30% in the fracture. Results from these experiments are not meant to be directly applied to the field, as experiments are not conducted at reservoir conditions. They are intended as a preliminary investigation into the potential of surfactant additives in hydraulic fracturing fluid


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