Tackling the Decline of Oil Recovery Method in Eastern Indonesia’s Mature and Remote Field: Carbon-Oxygen (C/O) Log

Abstract

This paper takes a focus on X Field, a mature oil field which is located in the Eastern Indonesia. The field has been producing from carbonate reservoir since 1970s, reached its peak in early 80’s and continually declining until present. The current low oil prices have resulted continuous improvement in many companies, particularly capital efficiency in producing hydrocarbons. Hence, low-cost well Interventions are one possible tool to maximize the oil recovery with less cost compared to new drills. The existing production zones are mostly being ignored due to the high water cut and recovery factor of around 98% and 43%, respectively. However, the new interpretation from the Carbon-Oxygen (C/O) log shows the remaining potential of untapped oils in the reservoirs that comes up with an effective and reliable approach to increase the lifetime of the field. The C/O log measures the oil and water saturation from low salinity reservoirs. The presence of carbon and oxygen is a substantial in the fluid interpretation process. The integration between C/O log interpretation and petrophysical analysis, helps to identify the current water saturations, especially near the existing perforations which changes from 98 to ~50 percent. Nevertheless, the water saturation at the un-swept interval which lying between existing zones and new zones increases the confidence to find the remaining oil in the reservoir. This method was applied before the intervention job, in order to confirm the un-swept remaining oil and water zones. C/O logs have been tested from the existing wells since 2016 and potentially boost up the Recovery Factor within the current economic situation. The Initial wireline logs from wells that were drilled 30 years ago are not reliable to be used as the justification for further interventions jobs due to the dynamic movement of fluids in the reservoir. Due to the successful utilizations of this method, the low cost-well Intervention jobs were applied to other 6 wells in 2017. The average improvement is nearly 60% increase and has been successful to eliminate risks that produce water from existing zones that still contain hydrocarbon. Integration between petrophysical analysis and C/O log analysis may provide an adequate distinguish between remaining oil and water zones in the high water cut reservoirs. Finally, this method of C/O log is expected to unlock the remaining oils in the other mature fields in different basins.

AAPG Datapages/Search and Discovery Article #90332 © 2018 AAPG International Conference and Exhibition, Cape Town, South Africa, November 4-11, 2018