Most of the discovered oil fields in Ukraine entering a declining production stage. Many of these assets have good potential for production increasing and require investments. The risks of such investments are related to the uncertainty of geological information, production data, and the total amount of reserves and resources. This paper describes the study of the joint use of 3D hydrodynamic modeling and reserves estimation according to the SPE-PRMS classification, which together allowed to assess and significantly reduce investment risks for oil production enhancement projects.

The use of 3D modeling is one of the key elements during field exploration and production, because of coordination of all available geological and field data it is often possible to discover new, previously unknown features of the geological structure and identify high potential areas to increase production. In this paper petrophysical, geological and hydrodynamic modeling tools and material balance method have been used to consolidate existing geological and field data and create 3D model of the field in Western oil and gas bearing region of Ukraine. Also, for uncertainty analysis of the initial hydrocarbons in-place and IOR project investment presentation the SPE-PRMS classification was used.

Comprehensive usage of material balance tools, field development history analysis, well performance changes, and fluid properties behavior revealed inconsistencies in the geological data and hypothesized the existence of a gas cap in the oil deposit and identify a faults system through the reservoir. After well logging these hypotheses has been confirmed, which allowed achieving a good history match of the model for the entire field and each well. Based on the matched model, a comprehensive field development strategy was proposed, which also considered all existing limitations related to production and infrastructure issues. The best scenario of field development was selected, according to the results of the economic assessment in terms of investment attractiveness. Based on the created 3D geological model, hydrocarbons reserves and resources were estimated using deterministic and stochastic methods and have been classified according to the SPE-PRMS. Reserves categories were assessed by the degree of commercial maturity of the project based on ten possible field development scenarios and high potential zones for infill drilling, plays exploration, and IOR project implementation was selected.

The integrated approach to the field development strategy assessment and the input data uncertainties allowed to consider all available geological information and field data to create a comprehensive pilot investment IOR project. The proposed approach allows to solve complex problems of potential investments risks assessment and reduction in IOR projects and discover new assets' potential on the example of a complex field in the inner zone of the Pre-Carpathian Depression.

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