| The process of frac'ing for oil or natural gas takes place in an extreme environment, where system components are subjected to very high pressures, torques, and vibrations. The result at many frac'ing sites is the failure of several mechanical components. This thesis analyzes the conditions that lead to the common failure of two components, a shaft in the transmission that drives the frac'ing pumps and the casing of the drill string, and seeks to present control solutions in the way frac'ing pumps are driven to reduce the failure rate of these components. Two primary models are presented, one of the pump and its powertrain and a distributed model of the vibrations within the well, and each model is simulated in MATLAB. Several control strategies to increase component longevity are incorporated into the two models and simulated to determine their viability. No obviously promising control solutions were found to increase the life of the transmission shaft, though the concept of active damping control is considered. While some data has been provided, further experimental stress and strain measurements along the drivetrain will be necessary to determine which damping control strategies are worth exploring further. A control solution was found, however, that is believed to improve well integrity. Simulations of the dynamics in the well reveal pressure fluctuations that are believed to degrade the drill string's concrete casing. It is later shown that synchronizing the crankpin angles in the frac'ing pumps can reduce these down-hole pressure fluctuations, and a control strategy is developed to synchronize the pumps. |
