Low Salinity Water Flooding: Proof Of Wettability Alteration On A Field Wide Scale

Abstract

Summary Low salinity water injection is an emerging EOR technology, applicable to mixed-to-oil-wet sandstone reservoirs. Flooding with low salinity water causes desorption of petroleum heavy ends from the clays present on the pore wall, resulting in a more waterwet rock surface, a lower remaining oil saturation and higher oil recovery. A secondary flood application is discussed in the Omar field in Syria showing a change of wettability from oil wet to a water-wet system. This change in wettability is supported by the observation of dual steps in watercut development. In between the two steps the watercut was constant. This behaviour is a known indicator of changing wettability. Moreover, direct connate water banking measurements confirm the change. The field observations are supported by spontaneous imbibition experiments in core material and a single well Log-Inject-Log test in an analogue field. From the field observations, the change in wettability is estimated to be nearly complete, leading to an associated incremental recovery of 10–15% of the Stock Tank Oil Initialy In Place (STOIIP). The significance of this work is that this is one of the very few documented proofs of concept on a reservoir scale. Work is ongoing to prove this concept in a tertiary flood as well.