Publications

Maximizing production and realizing optimal oil recovery becomes increasingly difficult as in-field drilling is less viable because of production history and economic issues. Thus optimization of production in existing wells by production enhancement and reevaluation of reservoir potential is increasingly important to contractor's cash flow and ultimate production profile. Petroleum engineers and geologists know reservoir characteristics from original well logs, but present rock properties and well conditions can only be determined from new cased-hole logs. During 2008-2009, cased-hole logs were run in five wells in CNOOC's Southeast Sumatra Ina Field - Ina E-07, Ina E-08, Ina T-01, Fara B-01, and Fara B-03. Based on log interpretation, several action plans were recommended to optimize production. The recommendations included additional perforations, squeeze cementing to shut-off water and gas, and re-perforation of some producing intervals. Remedial work based on cased-hole logging resulted in significantly improved production at Ina E-07 well. Ina E-07 has several intervals open and it was urgent to determine the interval producing gas since this well is lifted by electrical submersible pump (ESP). The problem zone was identified from cased-hole logs and isolated. Since then, Ina E-07 has been closely monitored. The amp chart now displays a smooth trend indicating the gas has been successfully isolated. Since remedial work, the well is producing 250-300 BOPD continuously compared to intermittent production before work over. Current pump life is 193 days compared to 70 days and 17 days from previous pumps. Economics are favorable as intervention costs of $241,000 have resulted in production of 38 MBO compared to two previous well interventions that cost $385,000 and yielded 22 MBO (run life and production as per November 19, 2009). The success of the field review and reevaluation has been discussed at the communication forum between contractor and government agency with the contractor now being encouraged to implement the remainder of the action plans to optimize production. Cased-hole logging is a valuable, cost effective tool for optimizing production in mature fields.