Single-well chemical tracer test (SWCTT) is a unique method that can be used to measure in-situ remaining oil saturation in the proximity of a well. The method has been used extensively to quantify remaining reserves in oil fields worldwide. It is also frequently used to measure the effect of different EOR techniques. Using a SWCTT-EOR-SWCTT sequence, saturation is established by an initial SWCTT, followed by an EOR-technique, and saturation is determined with the final SWCTT. The potential in-situ gain in oil production provided by the EOR can then be assessed by comparing pre- and post-EOR saturations.
In ideal cases, a SWCTT provides tracer curves that can be interpreted by means of simplified numerical or analytical models. In many cases, a variation in reservoir properties, pressure differences or reservoir drift complicates the tracer transport enough that a proper reservoir simulation model must be set up and solved to interpret the results of a SWCTT. Such models are usually complex enough that assisted history matching is required to optimize the parameters required to describe the physics of the problem.
In this paper we describe how state-of-the-art parameter estimation can be used to optimize a SWCTT simulation and demonstrate the work-flow using SWCTT data from a recent EOR test in West Africa. The work-flow is generic and can easily be adapted to any reservoir and tracer simulation tools that handle the reactive tracer transport required for SWCTT-modelling. We demonstrate that assisted parameter estimation is an effective tool to improve the interpretation of SWCTT results and provides significantly better and accurate remaining oil saturation from single well chemical tracer tests.