Case Study of 25 Years of Low Salinity Water Injection

Abstract

Abstract During the last two decades, low salinity waterflooding as a part of more general varying water composition has become a promising EOR method. Nevertheless, the physics mechanisms of extra oil recovery by low salinity waterflood are not clearly understood. Yet, fines migration and consequent permeability reduction may occur as a result of reduction of water salinity that can divert the water flux. This effect must be accounted in low salinity waterflood modelling. Moreover, the flux diversion due to induced-fines migration could be utilized to improve the reservoir sweep. In the current study the Tempest software is applied to build a model and history match 25 years of low salinity water injection in Bastrykskoye field (Russia). The model is then used to compare recovery factor for two scenarios of low salinity water (LSW) injection and formation water (FW) injection. The modeling results show an insignificant change in recovery factor between two scenarios of LSW and FW injection. This low incremental recovery is explained by the production of a significant amount of the reservoir water (FW) before the commencement of low salinity water injection. A sensitivity study shows that the location of the injectors can highly affect the incremental recovery obtained by LSW injection. A 2-layer model with 5-spot pattern shows a significant incremental recovery (8%) during injection of LSW as compared to the injection of formation water (FW).