Water Flooding Evaluation Methods for Clastic Reservoirs with Diverse Oil Viscosity in Central Asia

Water flooding extensively takes place in many mature oilfields of Central Asia. Due to the complexity of reservoir lithology and physical properties, as well as significant diversity in oil viscosity, there is a great challenge in water flooding evaluation by logs. This study mainly focuses on the water cut estimation and grading criteria of flooding in clastic reservoirs of three oil fields in Central Asia (reservoir burial depth: 300–2400 m, in-place oil viscosity: 3.9–417 mPa. s). By comparing reservoir geological conditions, different methods were suggested to calculate the initial oil reservoir resistivity (Rior). Based on the calibration of relative permeability experimental data and correction with production data, a new crossplot of resistivity decrease rate (RDR) versus water cut (Fw) with diverse oil-water viscosity ratios were developed. Furthermore, different grading criteria of flooding were proposed for these oil fields considering indexes of Fw and oil displacement efficiency (Ed). The flooding evaluation methods and grading criteria proposed in this paper are expected to offer practical applications and valuable references for conducting flooding evaluations in other water-flooded oilfields.