Interwell tracer method using partitioning compounds naturally existing in crude oil for determination of residual oil saturation

Tóm tắt

Beside the interwell tracer method in which the artificial tracers are injected into the reservoir, the method of using partitioning organic compounds in crude oil components such as alkylphenols and aliphatic acids as the Natural Partitioning Interwell Tracers (NPITs) to determine residual oil saturation (Sor) has drawn attention as a potential complementary method. Owing to the solubility into both oil and water phases, the concentration of NPITs in oil and also in produced water decreases along water injection time. Based on the similarity with chromatographic retardation principle used in the artificial interwelltracer method, residual oil saturation in the swept area between well pair can be determined by mean transit time from the concentration curve of NPITs analysed in produced water and partitioning coefficients K_d measured in the laboratory.

The paper presents the results of using NPITs to calculate Sor based on the data simulated by the UTCHEM simulator on the models of five-spot and direct-line. The results showed that the pairs of compound having partitioning coefficients K_d in range up to 3.0 can be used to estimate Sor in the injection stage from 1 to 3 pore volumes (PV) with 5% deviation from the Sor value given by the model. The paper also discusses the limitations of the proposed NPIT method that need to be improved and solved in future researches.