Offshore Automated Managed Pressure Drilling in Fractured Basement Granite Reservoir: Case study, Challenges and Solutions

Abstract

Abstract A2 well is a development well in a gas field discovered in the 1980s. This field is located in the offshore part of Southeast India. Prior to A2, the wells drilled in this field were tested with a significant sweet gas in the basement reservoir. The basement reservoir consists of a fractured granite formation with an estimated pore pressure of 9.22 ppg. Due to the presence of natural fractures in the reservoir, Automated Managed Pressure Drilling (MPD) technology was used to minimize loss of circulation and prevent substantial formation damage. Automated managed pressure drilling technology is used to help manage bottomhole pressure (BHP) precisely between narrow margins of pore pressure and fracture gradient by the application of back pressure on the annulus at all times. The system is automated by the use of a realtime hydraulics model, which takes into account the realtime parameters and calculates the required back pressure to maintain bottomhole pressure during drilling, connections, tripping, and well control situations. The paper describes the case study of the A2 well where automated MPD technology was used to safely drill the entire 8½-in. hole lateral section, which was difficult to support, and minimized any well control or drilling problems. The results show how MPD technology helped in delivering a successful well by eliminating drilling problems and controlling the flow rate of hydrocarbons to the surface while drilling, tripping and running the completion.