Publications

Rantau field is one of the main oil producing field in North Sumatera working area. The Rantau field has been produced by Pertamina EP Asset 1 Rantau since early 1970. The oil production from this field has declined in recent years and secondary EOR with waterflooding strategy has been performed to reduce the declining rate of oil production. The waterflooding strategy was done by updating the existing reservoir model based on open hole and production data. However, due to the reservoir complexity of Rantau field and unknown water salinity, it was difficult to validate the reservoir model based on the production data and resistivity logs derived saturation. Hence, in mid-year of 2016, it was decided to perform evaluation of the remaining oil in formation using Pulsed Neutron Logs –IC and Sigma evaluation for eleven wells, in which the tool offers salinity-independent oil saturation measurements using Carbon/Oxygen ratio. Rantau field also had a chance to evaluate these wells with a new generation of Pulsed Neutron Tool that provides multiple independent formation property measurements, which are sigma, neutron porosity, fast-neutron-cross-section, high precision spectroscopy and total organic carbon (TOC). The new tool is also able to perform direct gas measurements which can distinguish gas bearing from tight zones. Furthermore, the technology also enables to do simultaneous logging run for Sigma and IC mode that previously not possible with previous generation tool enhancing the operating efficiency of the data acquisition. A new interpretation method using these multiple measurements is detailed that can be tailored to many different scenarios encountered in cased hole logging and used to solve the desired reservoir saturations. The interpretation results which matched quite well with the available production data in candidate and offset wells were used as an up-to-date input for reservoir model and used to support waterflooding decision making.