Мурманская МИЛЯ. 2018 г. №4.

EXPLORATIONS Fig. 3 The unique seismic section crossing the North Pole Рис. 3 Уникальный сейсмический разрез, проходящий через Северный полюс (Fig. 3) [8]. The integrated geophysical survey per­ formed in the expedition made it possible to significantly strengthen the Russian argu­ mentation in justifying the outer limit of the continental shelf. In particular, a preliminary analysis of the CMP time sections made it possible to correlate the stratification of the sedimentary cover of the shallow-water shelves of the East Siberian and Chukchi seas and the stratification in the deep-wa­ ter Podvodnikov basin. On a qualitative level the general concept of new stratification was adopted. It will be presented in the applica­ tion from the Russian Federation to the Com­ mission on the Continental Shelf. For the first time ever CMP seismic survey was carried out along the straight lines in one of the most inaccessible regions of the Arctic, namely the Makarov basin. This allowed us to confirm the earlier ex­ pressed idea of Russian scientists a b o u t the rift-related nature of this basin. Informa­ tion on the velocities of seismic waves in the sedimentary cover that was obtained in the expedition as a result of seismic reflection and refraction soundings will allow correctly plotting depth sections along the acquired lines. Multicomponent Seismic in a Shallow W a ter Transit Zone 52 At the present time works in the shallow- water transit zone are the most important area of geological exploration. The majority of such areas remain poorly studied by mul­ tifold CMP seismic survey and belong to the most inaccessible water areas of the Arctic [11]. Shallow depths, very high tides, strong coastal currents, and generally unfavorable hydrological conditions lead to unjustified risks when using standard research methods. But on the other hand, these areas are stra­ tegically important targets for increasing the hydrocarbons resource base, primarily the shallow areas of the Priyamal shelf and the Pechora Sea, the promising structures on which have a marine extension and are rela­ tively accessible for their development from the shore [11]. The use of multicomponent bottom sys­ tems in seismic surveys makes it possible to improve the quality and increase the informa­ tional content of seismic sections. In addition to reducing the influence of surface waves on the hydrophone and increasing the signal- to-noise ratio in the bottom recorder, it be­ comes possible to record converted waves and to apply the technologies of multicom­ ponent seismic. Due to the 15-years working experience of our specialists in the transit zones of Rus­ sia, the technology of multicomponent data acquisition in the transition zone and in the extreme shallow water of the Arctic Shelf was developed. It makes it possible to record a seismic signal in the depth range of 0+1/50 m using a sea bottom cable-free system of autonomous seismic data acquisition (autono­ mous bottom recorders of OBX Geospace type manufactured by OYO Geospace Ind. (USA)). As a result, the single technology cluster of seismic surveys on the shelf, transit zone and onshore with high quality seismic data­ set was made. In 2013-2016 within the framework of four regional projects JSC MAGE carried out 2D-4C seismic surveys on the Arctic Shelf with a total volume of over 1,200 line km. The map of lines on the survey loops is shown in Fig. 4. When working with autonomous bottom recorders (ABRs), it is possible to implement acquisi­ tion geometry of any configuration with the required far source-receiver offset, limited only to the target horizons and the number of devices. It gives an opportunity to perform full-azimuthal seismic surveys. During the works the (OBX) Geospace autonomous bot­ tom 4-component module, which is a digital recorder with a continuous recording mode for the signal from the MP 18BH-1000 built- in hydrophone with 1-206 Hz (2 ms sampling interval) and the system of three OMNI-X- LT orthogonal geophones that record fre­ quencies in the range from 3 to 15,000 Hz were used. The received seismic response is digitally recorded in the built-in non-volatile memory. The recorder’s run time is 20 days. The receiver is equipped with an inclinom­ eter which makes it possible to determine the MURMANSK MILE • 4-2018