REAL-TIME PORE PRESSURE MONITORING OPTIMIZES DRILLING FOUR DEEP WATER WELLS IN KUTEI AND TARAKAN BASIN - OFFSHORE EAST KALIMANTAN

摘要

Oil and Gas exploration has led operators to explore the huge potential of deep water. But this exposes them to high risks of drilling through narrow mud weight windows with little margin for error. Hence, thorough planning and efficient and safe drilling practices are essential for a successful campaign. This paper is a summary of one such recent successful drilling campaign. ENI Indonesia, one of the largest operators in Indonesian deep water, drilled four deep water wells in Kutei and Tarakan basins, offshore East Kalimantan in 2010. The wells were drilled from a deep water drillship over varying water depths as much as 2700ft. A thorough pre-drill pore pressure study of the offshore basin was done using offset-well data for each of the four planned wells. The studies revealed presence of over pressure reservoirs with narrow drilling margin between pore pressure and fracture gradient. Best drilling practices were employed to drill these wells. One of which was real-time pore pressure monitoring onboard the drillship. The pore pressure engineer ran proprietary software, which enabled real-time streaming of Logging While Drilling (LWD) data such as gamma ray, resistivity with various depths of investigation, density and neutron porosity logs, ultrasonic caliper etc. Multiple pore pressure estimates were generated using various LWD logs in real-time. These estimates were analyzed in real-time in conjunction with drilling mechanics logs - rate of penetration (ROP) and weight on bit, Mud logs - gas volumes, pumps off gas during connection etc., cuttings shape and volume, Equivalent Circulating Density (ECD) and Equivalent Static Density (ESD), etc. to estimate the pore pressure. Pore pressure estimates were calibrated with wireline (MDT) and LWD (StethoScope), which recorded formation pressure estimates during drilling for improved look-ahead. Real-time pore pressure inputs to the drillers on the drillship and in town enabled several critical decisions such as altering casing depths and mud weight management.