The differential-normalized method of electrical exploration (DNME), by means of polarization study of the secondary sulphidation zone (depth ~ 0,4-0,6 km), allows making conclusion about existence and parameters of an oil and gas deposit (depth up to ~ 2-5 km). The approximate solution of the system of nonlinear differential equations in partial derivatives for concentration of sulfur-hydrogen and pyrite (polarizability) as the function of oil-gas deposit depth has been received. The results are confirmed by experimental investigations in the North Sea.
Intensive offshore exploration is being conducted at the present time. Due to areal alterations over the hydrocarbon deposits high pyrite concentration is accumulated. This effect results in induced polarization anomalies which can be discovered with differentially normalized electrical method. The survey is being carried out in the process of a vessel movement by six channels. dU(t) fields are obtained per one current pulse. These data are highly-correlated. Transformation of these data into orthogonal high dimension space as well as robust multivariate regression procedure application allow to distinguish the geological heterogeneities response. This investigation is developing the anomalies recognition technique.
In the procedure of the risk appraisal for a project of offshore towing of the large-size object, an algorithm of the «risk-management» is proposed to estimate the whole scope of assuming hazardous events. The initial – qualitative phase of analysis determines a possible range of risk factors, provides their description and classification. The second – quantitative phase evaluates their probability and subsequent cost values. The third stage of the risk values analysis – phase of the control – provides the cyclic recurrence of the risk-management. In sum, estimation of probable kinds of risks, while the towing, leads to ensured choice of compensating measures and, as a result, provides the needed level of security during the towing of, for instance, the jack-up rig platform.
