Polskaya 6-2024

N.N. Polskaya, A.Y. Samoylenko, D.A. Chukhnin, A.V. Ermolovsky, E.V. Kolesnikova, N.A. Khamzina

Oil samples containing hydrocarbon-based mud filtrate: assessment of contamination level and fluid composition restoration

DOI 10.47148/0016-7894-2024-6-85-90

Key words: mathematical modelling of oil treatment; contamination of fluid samples; hydrocarbon-based drilling fluid filtrate; contaminant removal method; subtraction method; openhole formation testing; fluid composition restoration.

For citation: Pol’skaya N.N., Samoilenko A.Yu., Chukhnin D.A., Ermolovskii A.V., Kolesnikova E.V., Khamzina N.A. Oil samples containing hydrocarbon-based mud filtrate: assessment of contamination level and fluid composition restoration. Geologiya nefti i gaza. 2024;(6):85–90. DOI: 10.47148/0016-7894-2024-6-85-90. In Russ.

The urgency of the work is determined by the need to obtain information on the true component composition of oils contaminated with hydrocarbon-based mud (OBM) filtrate. The authors discuss methods used to analyse contamination of OBM fluid samples. Two methods of quantitative assessment of formation fluid contamination are considered, they are: Skimming Method and Subtraction Method. Oil chromatography was used to determine hydrocarbon molar content in contaminated sample of oil and hydrocarbon-based mud, and the proportion of base oil in drilling mud was calculated according to the proportion. In order to determine oil contamination level, synthetic mixes of oil and hydrocarbon-based mud were prepared. Based on experimental data, contamination level was calculated using Skimming Method and Subtraction Method. Skimming Method showed the best result in contamination level assessment, while the Subtraction Method allows obtaining the restored formation fluid composition. It is shown that both methods need to be used together. In order to determine the applicability of the methods considered and to estimate the degree of restored and formation fluid matching, further investigations with formation fluid samples contaminated with filtrate of hydrocarbon-based (diesel-oil, crude and other hydrocarbon) mud are required.