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Automated Pressure Control for UBD Operations: Case Study and Field Validation


 In this paper, we present field results from a series of drilling operations where advances in sensor and control-system technology enable a high degree of automated pressure control in underbalanced-drilling (UBD) operations in Siberia, Russia. Traditionally, this fractured carbonate field was drilled conventionally using water as drilling fluid, accepting losses after hitting the first fractures, resulting in wells with access to only two or three fractures and not reaching target depth (TD) of the productive section. For these operations, a combination of nitrified water and crude oil was used. Applying automated pressure control with UBD equipment enables drilling with a controlled drawdown from the fractures, enabling the drilling of significantly longer wells, maximizing discovered fractures per well.
 In this paper, we show how the drilling of these wells has been achieved with the combination of sensors for managed-pressure drilling (MPD) and UBD and an automated pressure control system that maintains a constant drawdown throughout operations.