Drilling problems in depleted reservoirs

Abstract

New oil and gas wells are becoming more challenging to drill. New technology and better understanding of new and existing reservoirs become available, pushing the envelope of what is technically possible and economically viable. When new technology makes difficult wells possible to drill, more data is needed. Better understanding of what affects the drilling process is crucial in order to make the operation as efficient and safe as possible A lot of the new wells drilled today go into or through zones in the formation that have already been produced from. The reason for this could be that an existing reservoir needs to be drained from a different location in order to enhance the hydrocarbon recovery. Or it could that a new reservoir located below an older one is discovered or has not been possible to reach before. Lower pore pressure than what used to be present is encountered and this gives rise to problems and potential risks that have to be dealt with. When a formation is depleted from earlier fluid extraction, the operating window between the pore pressure and the fracture pressure for the section gets narrower. Due to these smaller tolerances, variations in drilling parameters will have a bigger impact on the downhole conditions. Knowing how different parameters will affect the downhole pressure is of great help. This aids in the design of a drilling program that can get a section drilled as a whole while minimizing the risk for operational hazards.