Мурманская миля. 2016, № 3.
EXPLORATIONS F ig .3 . Line laying by th e ice -b re a ke r. Р и с .3 . П ро клад ка проф иля л е д о кол ом . 20 extension of the continental shelf, which was performed by the Federal Subsoil Agency (Rosnedra) of the M inistry of Natural Resources and Environment. MAGE was in charge of arranging, planning and facilitating operations, supervising field work in general, and seism ic acquisition. Regarding the ice conditions the CMP reflection survey was conducted by using a 4,500 m long receiver (fluid) and a 600 m solid streamer combined with reflection/refraction sounding. The towing depth of the streamer and seismic signal excitation sources ranged within 10-15 m allowing airgun lines and the streamer to be securely deployed in conditions of ice concentration of 1 0 balls. Bolt 1500 and Bolt 1900/Bolt 8500APG airgun arrays with a volume of 1,300 cu. in. were used as excitation sources. The integrated hydrographic and geophysical survey was in excess of 10,000 km and included CMP reflection survey, seabed survey and gravity survey (F ig.2). The bulk of the survey was conducted in ice with a concentration of 9/10 and a thickness of up to 160 cm. Some lines came into contact with 2-year old ice as th ick as 240 cm and pressure ridges as high as 4 m. The Yamal icebreaker often had to push its way through the ice and then returned to make way fo r the Akadem ik Fedorov (F ig.3). The line made across the North Pole didn ’t appear to be something special (F ig.4). Integrated geophysical studies performed by JSC MAGE in 2014 allowed to considerably support argumentation of the Russian Federation when substantiating outer boundary of the continental shelf. In particular, the preliminary analysis of CMP time sections made it possible to tie stratification of the sedimentary cover of the shallow East Siberian and Chukchi shelves and that one of the deep-water Podvodnikov basin. MULTICOMPONENT SEISMIC IN TRANSITION ZONES The next point in the list of the key areas fo r our company is acquisition in transition zones. The shallow areas in the Yamal offshore and the Pechora Sea with relatively easy access to the resources are the assets of strategic importance fo r the hydrocarbon reserve base to be augmented. Most of these areas have been poorly explored. Shallow depths, high tides, strong coastal currents, generally adverse hydrological conditions create unreasonable risks in employing conventional methods of survey. For work to be done in the transition zone, MAGE employs the latest cable- free system of ocean bottom nodes fo r 4C acquisition. The autonomous ocean bottom 4C acquisition system OBX Geospace was chosen to be the data recording system as the most cost-competitive one (Fig. 5. Autonomous ocean bottom 4C acquisition system OBX Geospace). It includes an onboard central recording station and a set of ocean-bottom recorders. The Geospace autonomous mode four component unit is a digital recorder that ensures continuous recording of signals to the MP 18BH-1000 hydrophones and the three-component OMNI-X- LT geophones with a frequency range of 3 to 15,000 Hz. In 2013, the work was carried out in the transition zones of the Pechora Sea and the Yamal offshore which showed their efficiency and high quality of the seism ic data. The depicted section clearly shows that the quality of the transition zone data is comparable with that of seismic data conventionally acquired during vessels’ surveys. Furthermore, the projects completed in the Yamal offshore showed high information content of the data relevant both to the transition zone and land acquisition in onshore areas. A single technology cluster has been finally established for offshore, transition zone and onshore seismic acquisition projects. The works we have done in the transition zone and onshore offer a new level of technical advancement in the industry. MURMANSK MILE • 3-2016
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