Efficiency Evaluation Of Low Salinity Water Flooding(LSWF)in Carbonate Reservoirs

Carbonate reservoirs generally naturally fractured,oil wet and contain the utmost amounts of discovered oil reserves,greater than 60% of the reserves,are assessed to be contained in such reservoirs.Low Salinity Water Flooding(LSWF)in the past decade or so has been considered one of the evolving Improved or Enhanced Oil Recovery practice,since it’s an inexpensive and ecologically friendly secondary or tertiary enhanced oil recovery scheme for additional oil recovery from sandstone or carbonate reservoirs than other IOR or EOR methods.Unfortunately,LSWF essentially is still a vague conception,as its key mechanism is still unclear though intensely debated and experimented but still no general agreement has been accepted in view of its key mechanism.More interesting is the fact that,its effect in carbonates and its explicit mechanisms to an additional oil recovery have stood less studied and even less understood as compared to sandstones.The objective of this thesis is to present an experimental design to assess the effectiveness of LSWF in carbonate formations at a laboratory scale.Explicitly restricted to core flooding and contact angle measurement experiments using synthetic carbonate cores plugs and slices of dolomite mineralogy.Additionally,the study is limited to assessment of optimum water salinity through sequential dilutions of synthetic FW and an attempt to point out fundamental mechanism behind LSWF effect.The study employed a total of 18 experiments,12 core flooding and 6 contact angle measurements experiments.Moreover,the study utilized dead crude oil sample adapted from Middle East carbonate reservoir and eight synthetic brines(FW,2FW,10 FW,20FW,50 FW,100FW,200 FW and 500FW)and one distilled water.Core flooding experiments aimed at assessing the proficiency of LSWF in carbonate rocks through evaluating the additional oil recovery and attempting to point out the LSWF mechanism through the oilwater relative permeabilities.Additionally,Contact angle measurements were applied to further study the rock wettability change mechanism hence quantifying the LSWF effect through macroscopic contact angle changes.Besides,the Contact angle measurements were used to validate the core flooding experimental results.The experimental results exhibited that,with the reduction in the brines’ salinity the rocks’ wettability changes to a much less oil-wet state thus additional oil recovery.Likewise,there exists an optimal brine’s salinity(2384.6mg/L)at which maximum wettability change and consequently maximum additional oil recovery occurs.Hence its clearly that LSWF has a great potential in oil recovery and wettability change is the key driving mechanism behind it in carbonate rocks.