Applications of Equations of State in Blowout and Relief Well Kill Simulation
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A blowout is the most severe consequence of a well operation, and may cause a high negative impact on the surrounding environment and human safety, and financial distress for responsible companies due to clean up costs, penalties and degraded reputation. It should therefore be prevented at any cost, but human errors and mechanical malfunctions may lead to unpredictable incidents. However, if an accident resulting in a blowout occurs, several methods to regain pressure control over the well exists. One of these being a relief well kill operation. This report has primarily investigated how the reservoir fluid properties affects the total pressure losses and blowout rates during a blowout and relief well kill operation. As a preliminary work for this thesis, a PVT module was created and verified during a specialization project in 2015. The module is based on the concepts of equation of state and phase equilibrium, and estimates the fluid phase mole fractions and densities for a given fluid composition, pressure and temperature. For this report, the PVT module has been extended in order to estimate additional fluid parameters based on empirical correlations, such as viscosity, specific heat capacity and fluid surface tension. The PVT module was then merged with a blowout/relief well kill simulator created by Thoresen (2015). This simulator estimates the stable blowout conditions, which is satisfied when the bottomhole pressure is equal to the sum the well head pressure and the pressure losses throughout the well. Simulations have shown that the blowout rate decreases with increasing fluid density and mixture viscosity, and that a change in fluid surface tension does not affect the calculated pressure loss. Simulations have also shown that a small increase in light weight components with a corresponding decrease in heavy weight components of the reservoir fluid mixture may actually increase the oil blowout rate, due to lowered hydrostatic pressure loss in the well. Reservoir fluid composition and fluid properties does not affect the minimum injection rate to kill the well. However, the reservoir fluid composition may affect other aspects of the relief well kill operation, such as the time to kill the well.