Incremental Recoveries in the Field of Large Scale High Viscous-Elastic Fluid Flooding are Double that of Conventional Polymer Flooding

Abstract By conventional mechanism, polymer flooding decreases the Mobility Ratio and increases the Sweep Efficiency and Recovery of the reservoir, but does not increase the Displacement Efficiency (ED). However, from new understanding of the mechanism that driving fluid elasticity can increase the ED, Daqing Oil Field started 2 field pilot tests of high elasticity fluid flooding in year 2002, the actual recoveries are all more than 21%OOIP above that of water flooding, with incremental recoveries about double that of conventional polymer flooding (viscosity at 40~60 cp). Due to the very good results, in the recent 3 years, Daqing has rapidly expanded high viscous-elastic fluid flooding to more than 5000 wells. From the results of 1000 wells that have used this EOR method for a sufficient time to predict the results from field data, all will attain an incremental recovery of more than 20%OOIP; the other wells, according to numerical simulation, are performing as expected. Some new knowledge on the mechanism of viscous-elasticity of the driving fluid mobilizing residual oil is also presented. Field experience shows the difficulties in solving the problems of producing, pumping, gathering and treating produced fluid from high viscous-elastic floods are about the same as that of conventional polymer floods and much easier to solve than alkaline-surfactant-polymer (ASP) floods. The field results also show that the economics (costs per ton of produce oil) of this EOR method is about the same as conventional polymer flooding. In Daqing, very large scale high elasticity flooding is taking the place of conventional polymer flooding and ASP flooding to further increase the field recovery from 42% OOIP for water flooding to above 60%OOIP for high elastic fluid flooding. More than 2000 wells are converted to this method per year. This is a very promising new EOR method that could be used by itself or in conjunction with other Chemical EOR methods to significantly increase the recovery of many types of oil-fields.