Feasibility Study of Managed-Pressure Drilling with Automatic Choke Control in Depleted HP/HT Field

Abstract Drilling wells in depleted reservoirs is often characterised by a narrow operating window between formation pore pressure and fracture pressure. Drilling High Pressure High Temperature (HPHT) wells into a narrow margin reservoir is even more challenging, and Managed Pressure Drilling (MPD) techniques may be required in order to operate within safe limits. Managing the annular pressure profile during MPD operations requires a robust and reliable drilling control system. The presented work treats some challenges and possibilities regarding a MPD choke control system under evaluation for a planned HPHT well in the Kvitebjørn Field in the North Sea. Here pressure management is to be achieved by regulating the choke opening and thereby compensating for downhole pressure variations. Methodologies for automatic choke control during the drilling operation are assessed. A dynamic fluid flow model is used to calculate well pressures for application in the choke control algorithms, and to simulate pressure response in the well. The performance of choke control during drilling operations is evaluated and results from simulations are presented.