Enhancement of geological exploration efficiency and its risk mitigation during on the territory of Siberia and Arctic shelf

UDK: 553.982.2

DOI: 10.24887/0028-2448-2018-3-8-12

Key words: Siberia, the Arctic shelf, pressure, abnormally high pressure

Authors: B.L. Aleksandrov (Kuban State Agrarian University, RF, Krasnodar), Z.H. Mollaev (RN-Krasnodarneftegas LLC, RF, Krasnodar), G.I. Shilov (Gubkin Russian State University of Oil and Gas (National Research University), RF, Moscow)

The authors consider several questions of geological exploration efficiency and its geological and ecological risk mitigation on the territory of Siberia and the Arctic shelf under conditions of abnormally high pore (AHPP) and formation (AHFP) pressures. In these cases, especially within the Arctic shelf, holding trouble-free drilling and optimization of t productive horizons opening is impossible without an operational definition of geotagging in sections of wells and the study of patterns of development.

The opportunity to meet with the strata of rocks with abnormally high pore and reservoir pressures is illustrated on the examples of the well logging results of pressures assessment in wells of Messoyakha group of fields in the North of Western Siberia, and wells of Leningradskoye, Rusanovskoye, Kharasaveyskoye fields. The article presents examples of processing materials and evaluation of pressures for specific wells. So in well No. 2 of Sredne-Messoyakhskoye field we identified five zones of AHPP. The maximum gradient of the pore pressures in these zones is 0.15-0,16 MPa/m. In wells of Rusanovskoye and Leningradskoye deposits located on the Arctic shelf of the Kara Sea, we revealed three zones AHPP with maximum gradients of pressures up to 0,155-0.172 MPa/m. The data obtained allowed to recommend the optimal design of wells and density of drilling fluids.

It is shown that the cause of AHPP is lithogenetic factor when compaction of clay rocks occurs at the complicated outflow of pore fluid. The genesis of AHFP in sand and siltstone reservoirs of these deposits may be associated with a combined mechanism of formation of anomalously high geofluid pressures. Here along with lithogenetic factor, there are also processes of vertical migration of fluids from sources of gas in the sedimentary cover. On the basis of the analysis the conclusion is made that it is necessary to create a permanent center for the promotion of well drilling with continuous assessments of geofluid pressures, areas of AHPP and AHFP logging and technological parameters of drilling.

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