Abstract
This paper presents several alternative ways of using partitioning interwell tracer tests (PITTs) in oil fields for the calculation of oil saturation, swept pore volume and sweep efficiency, and assesses the accuracy of such tests under a variety of reservoir conditions. The method of moments is used for the interpretation of PITTs in heterogeneous reservoirs with spatially variable residual oil saturation and extends the method to cases with mobile oil saturation. The feasibility of using partitioning tracers to estimate oil saturation at different depths in the reservoir was investigated assuming that the tracer concentrations could be measured with downhole chemical sensors or any other suitable method. The possibility of using natural organic tracers (dissolved components of the crude oil) as a low-cost alternative to injected tracers was also simulated and the method of moments was used to interpret the results for both single porosity and dual porosity reservoirs. All of these applications point to a much greater potential for the PITT technology than is commonly recognized or practiced in the oil field. The results clearly demonstrate that the method of moments is a very simple, fast and robust method to estimate oil saturation and swept pore volumes from either injected or natural partitioning tracer data.
