Evaluation of Residual Oil Saturation After Waterflood in a Carbonate Reservoir

Four different approaches, including special core analysis (SCAL), log-inject-log, thermal-decay-time (TDT) logs, and material balance, were used to narrow the range of residual oil saturation (ROS) after waterflood, S[sub orw], in a carbonate reservoir in Qatar to between 23% and 27%. An equation was developed that relates S[sub orw] with connate-water saturation, S[sub wi], and porosity. This paper presents the results of S[sub orw] determinations with four different techniques: core waterflood followed by centrifuging, log-inject-log, TDT logging, and material balance.