Approach to localization of oil-water contact during reserves estimation

UDK: 622.276.031:532.51(1-04)ВНК

DOI: 10.24887/0028-2448-2025-7-40-47

Key words: oil-water contact, specific electrical resistance, transition zone, position of initial fluid contact, oil-water contact substantiating scheme, capillary model, porosity and permeability properties

Authors: V.G. Bazarevskaya (TatNIPIneft, RF, Almetyevsk); D.V. Anoshin (TatNIPIneft, RF, Almetyevsk); R.R. Hanbikova (TatNIPIneft, RF, Almetyevsk)

In oil field geology, the oil-water contact is the boundary separating oil from water in a reservoir, which is a zone of varying thickness containing oil and free water. An important task is to localize an oil-water contact, or position of the initial fluid contact in newly discovered deposits and fields under exploration, along with identification of oil-bearing layers. Oil fields in the Volga-Ural oil and gas province are characterized by complex geology and variety of oil reservoirs, including both conventional and unconventional reservoirs. Accurate determination of oil-water contact is of a great importance in volumetric estimation of reserves and serves as a significant parameter affecting the initial-oil-in-place distribution in the fields. In some cases, determination of fluid contact is complicated by a transition zone, particularly, in carbonate reservoirs. Based on the studies, the range of a transition zone variation can be from several meters to over 10 m. This fact adds complexity to oil-water contact determination. This paper presents approaches to identifying oil-water contact and analyzes the main problems affecting fluid contact substantiation. The results of the research will enable the use of the presented approach to fluid contact determination during reserves estimation, planning of prospecting and exploratory drilling, as well as geological exploration activities.

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