Geological and economic efficiency of the use of gravity and magnetic exploration at different stages of geological exploration

The paper presents the results of geological interpretation of gravi- and magnetometry data in conjunction with seismic materials acquired in several areas of the Laptev Sea, Barents Seam and Pechora Sea shelfs in different exploration stages: regional and prospecting together with 2D and 3D seismics. Regional airborne gravity and magnetic surveys in the Laptev Sea resulted in updating geological structure of the Anabar-Khatanga Saddle sedimentary cover, namely: outlines of anticline structures, occurrence of salt diapirism and tectonic deformations. Subsequently, this information was helpful in planning 2D seismic surveys. The geologists of the project qualified the marine gravi- and magnetometry data obtained in the Pechora Sea together with 2D seismic survey as “road maps”. Potential fields and their continuations were actively used during the course of structural interpretation to trace faults, main structure-forming thrusts, oblique thrusts and build a structural and tectonic model of the Vashutkino-Talotinsky fold and thrust zone. Is the stage of 3D seismic survey in the Barents Sea, the accompanying gravi- and magnetometry allowed obtaining additional information on geological structure of sedimentary cover and basement of the Admiralteisky Swell. In particular, numerous plutonic formations are found in sedimentary cover. Magnetometry in conjunction with geotechnical surveys allowed revealing dikes and sills, which were accounted for in preparing the hazard map for the designed site of well construction. Relative costs of the works and mitigation of geological uncertainty were estimated for all the presented projects. They confirm geological practicability and economic feasibility of seismic, gravity, and magnetic surveys within the framework of exploration and prospecting for oil and gas, particularly in the case of complicated geological architecture of the regions under investigations