Abstract

Successful implementations of Single Well Chemical Tracer (SWCT) Tests have opened up new opportunities for reserves growth in North Kuwait reservoirs with water flood and with use of Enhanced Oil Recovery methods (EOR). Series of SWCT Tests have been carried out with water flood and ASP (Alkaline Surfactant Polymer) as a part of the EOR project in Sabiriyah Mauddud (SAMA) reservoir to evaluate the efficiency of chemical EOR agent (ASP) in reducing the residual oil saturation. SAMA reservoir is very heterogeneous carbonate reservoir and results of SWCT tests reflect the reservoir complexity of SAMA. Produced tracer profiles do no show a sharp identifiable peak as seen in case of tests conducted in sandstone reservoir. Though these tests provided valuable information about residual oil saturation with water flood (Sorw) and residual oil saturation with ASP injection (Sorc), a need was felt to model these tests to have a better understanding of the controlling parameters affecting tracer concentration production profile. The SWCTT modeling will also help in reducing the impact of uncertainties in future planned tests.

Two single well models have been built using STARS simulator of CMG to simulate four SWCT tests conducted in two wells. This is considered as the first simulation study of SWCT tests conducted in North Kuwait Asset, KOC. Detailed sensitivity analysis has been carried out to match Tracers concentration profiles using (i) Single porosity and single permeability model, (ii) Dual porosity dual permeability model and (iii) Drift model. In addition to that, various history match parameters of dispersion, diffusion and dispersivity have been tried to get a reasonable match.

First, major emphasis was given to material balance tracer (IPA) and cover tracer (NPA) profiles during history match because these tracer profiles are not affected by reaction rate and there are no signs of dilution or drift effect observed. The perfect match in material balance tracer indicates that reservoir characterization of the model is good. After that, reactive and product tracers were matched using different magnitudes of Dispersivity and Reaction rate.

The paper brings out the findings of simulation studies performed and discusses the main controlling parameters affecting tracer concentration profiles during SWCT tests in such heterogeneous carbonate reservoir.

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