Мурманская МИЛЯ. 2018 г. №4.

EXPLORATIONS are performed in accordance with differential technique using several magnetometers. The USBL positioning system is applied for the survey systems operation control. For the bottom sampling standard sam­ pling techniques as well as new vibro-coring samplers which allow collecting of unbroken cores up to 6 m long (Fig. 1) in complex en­ vironment are used. Next we come to innovative technologies. High resolution and ultra-high resolution seismic is primarily used for detailed section­ ing of the upper layer in order to identify gas lenses and gas-hydrates accumulations as well as for shallow gas accumulations fore­ casting [4, 6]. Current identification of gas accumulations is a relevant objective in ex­ ploration and development of petroleum fields on the shelf. Excess pressure of forma­ tion occurring in such gas pockets pose risk for wells construction and underwater facili­ ties arrangement. An emergency at the well in the Sea of Okhotsk focused attention at this problem [7]. The most important component of high reso-lution seismic technique is a recording system based on a special seismic streamer involvement. At present during the period of sanctions in order to perform this type of sur­ vey we use modern equipment with almost the same parameters produced in Russia by Si Technology (Gelendzhik). It is a Russian 192-channel digital streamer of XZoneBottom- 42 Fig.1 V ibro-corer GEO-VIBRO CORER 3 0 0 0 + 6 0 0 0 Рис. 1. Вибрационный проботборник GEO-VIBRO CORER 3 0 0 0 + 6 0 0 0 Fish type with the active length of 1,200 m. A distinguishing feature of the recording sys­ tem is a reduced interval between the streamer channels (6.25 m and 3.125 m) that make it possible to sufficiently increase the detail of a seismic section [1]. Penetration depth is about 1 km under the resolution capability of 2-5 m depending on the geological structure of the sedimentary cover [5]. The results of surveys recently performed with the use of high-resolution seismic tech­ nique demonstrate its high efficiency and in­ formativeness for the detailed identification of different types of rock units of the section upper part in order to identify gas lenses and gashydrates accumulations. There have been explored the license areas of Gazprom and Rosneft in the Sea of Okhotsk and in the Kara Sea [4, 6]. In this article we shall describe in details surveys involving ROV (remotely operated ve­ hicle). In order to perform special engineering surveys MAGE purchased a vessel which was named Fedor Kovrov in honour of the MAGE employee who had fought here in the Po­ lar region in a partisan group. The vessel is equipped with the dynamic positioning system and is supplied with the ROV on board which is installed in the 20-feet container [2]. The system is equipped with cameras, so­ nar and a hydraulic manipulator. There are tools for water, sediments and gas phase sam­ pling installed on it. There is a wide range of tasks to perform with this system: • general visual inspection of project pipe­ line routes and area inspection including HD video recording; • side scan sonar, multibeam echo soun­ der and magnetometer target inspection using scanning sonar and magnetic gradiometer; • seawater, soil and gas sampling; • marine growth cleaning of any underwa­ ter surfaces using cavitation cleaning system or mechanical brush fitted with Osborn clean­ ing brushes; • cathodic protection system monitoring using CP probe; • measuring of wall thickness of underwa­ ter pipelines through the isolation using the ul­ trasonic thickness meter; • buried cables and pipelines tracking using pipetracker including tone generator; • underwater structures positioning, pitch and roll measurements; • underwater pipelines inspection using wheeled-skid equipped with profilers and video cameras on booms; MURMANSK MILE • 4-2018