Case study of low salinity water injection in Zichebashskoe field

Abstract

Low salinity waterflooding is a very promising EOR method in recent years. The mechanisms of enhanced recovery are considered to be decrease of residual oil saturation and alternation of rock wettability. In addition, the mobility control mechanism due to induced fines migration by low salinity water, and the consequent flux diversion is also a possible mechanism for enhanced recovery in low salinity waterflooding. The current paper analyzes production and injection history data from 24 years of production from Zichebashskoe field (Russia) which includes 7 years of low salinity water injection. The mathematical model for waterflooding with fines migration is applied for history matching. The result is a good agreement between the field history and modelling data. The Roxar tracer model is then used to compare recovery factor for two scenarios of low salinity water injection (field history) and conventional water injection using formation water (High salinity). The results shows insignificant incremental recovery (< 0.1%) and decrease in the amount of produced water during the development of Zichebashskoe field. It can be explained by the production of significant amount of the reservoir water (> 45% of total produced water) before the commencement of low salinity water injection and also injectors placing. A two layer cake reservoir is built using Zichebashskoe field permeability distribution to study the effect of low salinity water injection in a 5 spot pattern. Modeling results show significant improvement in oil recovery (~10%) and large reduction of water cut.