Almost all major oil fields of the Republic of Tatarstan are at the last stage of development. Maintaining the current level of hydrocarbon production requires availability of reserves. TATNEFT extensively considers the opportunities for company capitalization growth, particularly by means of bringing into development production targets that previously have been of no commercial interest due to complex recovery mechanisms. Such targets are confined, for example, to Devonian carbonate sediments occurring from the Zavolzhskian through the Sargaevskian horizons.
The article analyzes the current resource base status based on reserve volumes estimated by different methods using the example of Semilukskian-Mendymskian carbonates within the pilot area of the Romashkinskoye oil field. Out of dozens globally used resource assessment methods, three methods were considered. These are Russian Classification of Reserves (Russian Federation Ministry of Natural Resources), probabilistic-statistical method (Monte Carlo method) and United Nations Framework Classification. Russian Reserves Classification is based on volumetric method. It is the primary method for companies that carry out exploration activities in Russia, as it is applicable for estimation of resources with any reservoir drive mechanism and any category of reserves. The volumetric method relies on determination of oil or free gas volume at standard conditions of reservoir rocks. Monte Carlo method is based on probabilistic-statistical assessment of resources with account of geological risks. It enables consideration of the effects of several parameters selected during sensitivity analysis on the outcomes and statistical assessment of project perspectives. Application of probabilistic models allows to consider the uncertainty of resource assessment at early exploration stages and assess a viability of promising areas and fields development. United Nations Framework Classification is intended for determination of environmental and social-economic viability and technical feasibility of development projects and assessment of reliability of estimated future production data. It is concluded that improved accuracy of reserves estimates and continuous engagement of prospective resources requires a broad-minded approach and application of different resource estimation methods.
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