Abstract
Heavy oil makes up approximately 15 percent of the world's remaining oil reserves. It presents opportunities that could be commercially viable but often rejected because of the inherent challenges of producing them, especially in offshore environments. These challenges include flow assurance, produced water separation and treatment and additional heat and power requirements. The common occurrence of low API reservoirs at relatively shallow depths can lower drilling and completions costs but can also increase production and transport costs and limit marketing options.
This paper describes the commercially successful production of a heavy oil reservoir offshore Niger-Delta. The field was discovered in 1968 and an appraisal well was drilled in 1970. At that time, the accumulations were deemed to be too small to develop. Forty years later the economics of oil production had changed and additional appraisal wells were drilled. Modern logs, core and MDT samples were taken. Three of the five reservoirs contained heavy oil. Reservoir simulations established initial estimates of recovery for each reservoir encountered and IPM models established inflow-outflow relationships. For the heavy oil reservoirs, the IPM showed that artificial lift would be required to produce the oil. This was confirmed by failed attempts to naturally flow an appraisal well that tested the best of the heavy oil reservoirs. The decision was taken to drill a horizontal pilot producer completed with a downhole ESP. The pilot producer was successful and several development wells were subsequently drilled in that reservoir and completed with ESP and gas lift capability.
This paper further showcases how the economics of producing a heavy oil reservoir was reversed by comingling with lighter crude and managing the challenges of crude compatibilities, produced water separation and marketing of the crude blend.
