Date of Graduation
Statler College of Engineering and Mineral Resources
Petroleum and Natural Gas Engineering
H Ilkin Bilgesu
It is critical to understand the dynamic behavior and consequences of undesired reservoir influxes that triggers well control emergencies. In contrast to liquid kick, gas influx migration in water based mud and solubility in oil based mud represents exceptionally hazardous conditions. Operation delay time would result in a pressure build-up at the surface with increasing risk of fracturing the casing shoe.;In this study, critical factors affecting gas bubble rise velocity in a closed wellbore are studied. These factors are influx size, annulus clearance, reservoir pressure, oil/water ratio, drilling fluid density, reservoir temperature, plastic viscosity and yield point. Three different well types (vertical, directional and horizontal), well deviation angle and wellbore configurations are considered. Gas rise velocity and pressure changes at the surface and bottom hole are monitored at different well shut-in periods of time. A commercial multi phase dynamic well control simulator utilized with a common well configuration.;Preliminary results show that higher gas rise velocities and wellbore pressures are experienced as the severity of the encountered conditions increase due to high reservoir pressure as well as the influx size. In comparison to vertical and directional wells, horizontal wellbore trajectory experiences the lowest surface and bottom hole pressures. The average gas rise velocity in WBM is 82.2 ft./min, while in OBM the average gas rise velocity is 31.96 ?ft./min. In addition, in OBM while the gas is migrating to the surface, wellbore pressure increases then free gas dissolves completely and stays stationary.
Guner, Seyhmus, "A Study of Pressure Variation in Wellbores During Gas Kicks" (2017). Graduate Theses, Dissertations, and Problem Reports. 5723.