Risks are inherent practically in all sphere of oil and gas production: from geological exploration works on oil and gas to industrial development of reserves. But it is not enough to study only risks, we often face insufficiency of knowledge of variety of manifestations of geologic-geophysical trade properties of the studied object. It is especially important to consider risks and uncertainty at the initial stages of geological field works. Studying of geological risk, arising at estimation of oil reserves became a subject of our research. The work process was divided into some stages: 1) Choice of significant geological field parameters, 2) Definition of variable property manifestations factors of the studied geological field parameters, 3) Multiple modeling of the studied processes, 4) Creation of Tornado plot For further work, the analysis of an assessment of risks at reserves estimation was chosen as a probabilistic method. It was chosen hypothetical fields which subcalculating parameters, were collected in tables Using the data provided to the table, we make Tornado Plot extent of influence of geological risks is visually shown in the made matrix. The made matrix reflects degree of risks in an assessment of subcalculating parameters and their influences on resultant indicators. The vertical scale reflects risk, which is classified on low, average, high. Using the results received in the analysis of uncertainty and a scale of influence of parameters on resultant indicators and a scale of level of risks, geological field parameters were located on the constructed matrix. From the received matrix, it is visible that among the taken parameters the greatest risk and high level of influence renders porosity. Therefore, the bigger attention at calculation of stocks and creation of geological and mathematical model has to be paid to this parameter.

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The faults are universal in the petroleum reservoirs. Some of them are Semi-Permeable Filtration Barriers (SPFBs) such that a SPFB becomes fluid/gas permeable if a pressure threshold is exceeded. This may cause sudden changes in reservoir structures and, eventually result in negative impacts on production. This paper deals with early SPFB detection and characterization. We consider some case studies of reservoirs with SPFBs, and present a new methodology for SPFB detection. This includes the following groups of methods: mapping of surface responses to deep geodynamic and fluid-dynamic events (incl. SAR interferometry), 3D-mapping of faults in the reservoir and adjacent formations, separation of SPFBs from other dislocations. The methodology implementation is demonstrated with the case study of underground gas storage.

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