Systematic Diagnostics and Real Time Reservoir Monitoring in a High GOR Horizontal Well To Detect the Source of Gas: A Case Study in Panna Field, Western Offshore, India

摘要

The Panna field, located offshore the western coast of India is a carbonate reservoir with a thin oil rim (~20m) sandwiched between a gas cap and a large bottom aquifer. The field comprises of two main layers - 'A' zone gas cap and 'B' zone which is the main oil producer, separated by an interface. As the vertical/horizontal permeability ratio is high (~1) this reservoir is highly susceptible to coning problems. Horizontal multilateral wells were drilled in 'B' zone to achieve maximum reservoir contact with minimized gas coning. These wells are equipped with permanent downhole gauge to monitor conditions downhole in real time and auto gas lift to use energy from the gas cap to lift fluids from the oil reservoir when required in future. However, in first such well unwanted high gas production raised doubt on the completion integrity and on the possible communication between two zones. This necessitated a thorough troubleshooting to detect the gas source for corrective action afterwards. This case study presents the methodology applied in detecting the source of the abnormal high gas production using Production Logs & Permanent down hole gauge using auto gas lift diagnostics. The diagnosis, carried out in phases, enabled us to pinpoint a highly unlikely source by removing all other possibilities such as leaking Auto Gas Lift, communication between zones, seal bore integrity failure. This was confirmed by production logs which indicated a leak in Full Bore Isolation Vale vent ports and confirmed that Auto Gas Lift is functioning properly. These findings were significant as the well was saved from a possible workover or sidetrack and production was enhanced as well.