No.3(43),2025 PP.150-169

Neftyanaya provintsiya No. 3(43), 2025

Rough consideration of changes in formation and oil compressibility during unsteady-state flow

V.A. Iktissanov, A.V. Iktisanov, M.S. Bernatov
DOI: https://doi.org/10.25689/NP.2025.3.150-169

Abstract

Existing software packages for reservoir simulation, production analysis, and well test interpretation rely on linear and, much less often, exponential dependences of porosity on pressure. Various studies, including those conducted by Terzaghi K., suggest a logarithmic pressure dependence of porosity and hence inverse relationship between formation compressibility and pressure. Similar pressure dependence is observed for various oils according to Vasquez M., Beggs H.D. In light of the above, a rough algorithm for estimation of diffusivity equation is proposed and tried out with account of inverse pressure dependence of compressibility, the order of proportionality coefficients for oil and rock is defined. Estimation results suggest that should the factor under current discussion be neglected, then erroneous overestimation of skin factor, underestimation of permeability, and substantial underestimation of the distance to formation boundaries are observed. The latter point is the most important for reserves estimation based on well test data from wildcat and exploratory wells. The main differences from linear flow are defined by contrasting compressibility factor and inverse function of compressibility versus pressure. The most pronounced effect from the proposed approach compared with linear flow is observed for high oil and formation compressibility and large pressure drawdowns.

Key words:

diffusivity equation, well tests, compressibility versus pressure, porosity, oil, rock, pressure

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Authors

V.A. Iktisanov, Dr.Sc., Professor, Oil Field Development Department, St. Petersburg Mining University of Empress Catherine II
2, 21 Line, Vasilyevsky Island, 199106, Saint Petersburg, Russian Federation
E-mail: iktisanov_va@pers.spmi.ru

A.V. Iktisanov, Student, Moscow Institute of Physics and Technology (National Research University)
9, Institutsky Lane, 141701, Dolgoprudny, Moscow Region, Russian Federation
E-mail: a.iktisanov@yandex.ru

M.S. Bernatov, postgraduate student, St. Petersburg Mining University of Empress Catherine II
2, 21 Line, Vasilyevsky Island, 199106, Saint Petersburg, Russian Federation
E-mail: s245042@stud.spmi.ru

For citation:

V.A. Iktissanov, A.V. Iktisanov, M.S. Bernatov Priblizhennyy uchet izmeneniya szhimayemosti kollektora i nefti pri neustanovivsheysya fil'tratsii [Rough consideration of changes in formation and oil compressibility during unsteady-state flow]. Neftyanaya Provintsiya, No. 3(43), 2025. pp. 150-169. DOI https://doi.org/10.25689/NP.2025.3.150-169. EDN NMWBPO (in Russian)

© Non-governmental organization Volga-Kama Regional Division of the Russian Academy of Natural Science, 2015-2025 All the materials of the journal are available under the Creative Commons Attribution 4.0 License (https://creativecommons.org/licenses/by/4.0/)

Rough consideration of changes in formation and oil compressibility during unsteady-state flow V.A. Iktissanov, A.V. Iktisanov, M.S. Bernatov DOI: https://doi.org/10.25689/NP.2025.3.150-169

Key words: diffusivity equation, well tests, compressibility versus pressure, porosity, oil, rock, pressure

Rough consideration of changes in formation and oil compressibility during unsteady-state flow

V.A. Iktissanov, A.V. Iktisanov, M.S. Bernatov
DOI: https://doi.org/10.25689/NP.2025.3.150-169

Key words:

diffusivity equation, well tests, compressibility versus pressure, porosity, oil, rock, pressure