Effect of water depth on bridging tendencies in ultradeepwater blowouts in Gulf of Mexico
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A blowout is an uncontrolled flow of reservoir fluids into the wellbore to the surface, causing serious, sometimes catastrophic, problems in different types of petroleum engineering operations. If the formation's strength is low and the pore pressure is high, bridging can be a very effective method for blowout containment In this method, the formation caves into the open hole or onto the casing and stops the flow of the formation's fluid, either naturally or intentionally. This method can be effective in deepwater blowouts where the formation has high pore pressure and considerable shale intervals with low strength. In this paper, wellbore stability and fluid flow performance subroutines have been developed with Visual Basic for Applications (VBA) programming. By integrating the subroutines together, we made a simulation tool to predict wellbore stability during blowouts and, consequently, predict wellbore bridging during normal and blowout situations. Then we used a real case in the country of Brunei to investigate a field case of a bridged wellbore to validate the simulator. Based on this simulation tool we are able to determine the potential location of bridging during the blowout situation and compared the model with real data and field observations during normal and blowout situations. The difference between our simulator and existing models is that existing simulators only determine breakouts in static situations not during the blowout. In the final part of this paper we studied the effect of water depth on bridging tendency during a blowout for the deepwater Gulf of Mexico (GOM). Since we could not find much real data in this area, we used general trends and correlations related to the GOM for parts of our study. The results of our study showed that water depth delays the occurrences of breakout in the wellbore during blowouts (i.e. for greater depth of water, wellbore collapse occurs farther below the mudline). However, the depth in which collapse occurs is different for different maximum horizontal stress amounts. Copyright 2006, Society of Petroleum Engineers.
