In this work we present field results from a series of drilling operations where advances in sensor and control system technology enables a high degree of automated pressure control in under-balanced 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 draw-down from the fractures, enabling drilling of significantly longer wells, maximizing discovered fractures per well.
In this paper it will be shown how the drilling of these wells have been achieved with the combination of sensors for MPD and UBD and an automated pressure control system that keeps a constant drawdown throughout operations.