Case Study: First Ever Implementation of Managed Pressure Drilling to Drill Exploratory and Near Wildcat Well at Ongc Tripura Asset

Abstract

This paper describes the use of managed pressure drilling (MPD) and managed pressure cementing (MPC) technology on a high-pressure high-temperature (HP/HT) well in North-Eastern onshore, India by Oil and Natural Gas Corporation Ltd. (ONGC), a leading exploration and production company in India in collaboration with Halliburton, one of the major oilfield service providers globally. The bottom-hole temperature recorded in this well is 151°C and bottom-hole pressure of over 15,000psi at target depth. The MPD technology was utilized for drilling the well for the first time in ONGC. The near wild cat well was successfully drilled and cemented to a depth of 4,840 mMD and made history by tapping into Lower Bhuban and Barail sands for the first time, while successfully drilling in uncertain pore pressure environments, managing gas and water kicks, coping with loss zones, and identifying production zones together with pore pressure estimation. The well posed many challenges including uncertain pore pressures, highly unstable formations, likelihood of differential sticking and high-pressures/high-temperatures. The operator had attempted to drill the well conventionally in the past which had to be abandoned due to technical complications owing to high pore pressure gas and water sands as well as high differential pressure. MPD uses a closed-loop system that adds an increased level of environmental protection and allows for the use of an automated early kick detection system for increased safety. The automated MPD system was incorporated for the two well sections (12-1/4" and 8-1/2" hole sections) to provide control, flexibility, and safety required to drill and mitigate these risks. This implementation allowed to drill 2,013 meters (6,604 feet) in an extremely challenging zone in stable and safe conditions. The well was drilled to a target depth of 4,840 meters (15,880 feet). Deployment of an extensive MPD surface control system (along with rotating control device, fully automated choke manifold and back-pressure pump) allowed drilling and cementing of the well in a safe and efficient manner without any breach to safety and service quality. The MPD technology enabled ONGC to reduce the mud weight while drilling the well by balancing the formation pressure with application of additional SBP from surface using MPD choke manifold. This helped ONGC tackle the narrow drilling window along with early-kick management in HP/HT environment. The well was drilled to target depth of 4,840 mMD, making it the deepest drilled and cased hole in Tripura, Asset India. Major formation information on Lower Bhuban and Barail sands was obtained along with ascertaining zones of interest by allowing early detection of formation changes and hydrocarbon zones. The formation was non-drillable through conventional approach and implementation of MPD technology made it possible. The operation was carried out with extensive remote support from team in global and region considering pandemic situation.