India's 1st Polymer Flood Scheme Implementation from Laboratory to Field in Heavy Oil Having Strong Aquifer

Abstract

Abstract The case studies for Polymer flood globally in heavy oil are few and far between. The low primary recovery of this field warranted an EOR scheme. The present paper discuss the challenges in designing & implementing a polymer flood project in a heavy oil field in a strong aquifer drive with vertical well configuration. The paper covers a complete EOR cycle from screening, laboratory studies, simulation studies, pilot execution and further full field implementation. EOR screening was carried out through established screening methods to find a suitable EOR technique. Post screening, polymer flooding was tested in the laboratory and based on the encouraging laboratory findings, it was recommended for simulation studies. Sector modelling with fine grid scale of 16*16m carried out for pilot simulation study. Polymer Pilot scheme was designed and successfully implemented in the field in May-2019. After Successful pilot execution, history match of the polymer pilot was carried out. Learning's from the pilot study were incorporated in the model and full field scheme was implemented in the field in Oct-2022. Thermal stability tests for various polymers were carried out in laboratory and thermally stable polymers were shortlisted. Similarly, test for adsorption and screen factor was carried out and suitable polymer was shortlisted for core flood experiments. Core flood experiments carried out on sand pack made from native sand of the reservoir. Based on the mobility ratio and shear thinning properties of selected polymer, polymer viscosity was taken as 25cp. Polymer flood linear core displacement efficiency was found 61.4%. Incremental displacement efficiency was 17% over water flood. After laboratory experiments simulation study was performed for polymer pilot. Sensitivity carried out for number & type of patterns, pilot site, injection/production rates, residual resistance factor (RRF) and pore volume injection. Based on simulation results a normal 5 spot pattern was proposed for field execution. Envisaged incremental recovery over base case was ~12% of target oil. Expected oil recovery was achieved in pilot and water cut reduced from 80% to 60%. History match of pilot was carried out in the black oil simulator. After pilot history match full field scheme was prepared and implemented in the field in Oct-2022.Incremental recovery envisaged in full field scheme over base is ~ 5%. This study has proved that polymer EOR can enhance oil production in heavy oil with strong water drive. This project paved way forward for other analogous fields. A standard methodology was adopted to implement polymer flood in all analogous fields of the company with low recovery. The experience and expertise gathered from this study has given courage to implement full field polymer EOR in analogous fields without pilot study.