Мурманская миля. 2016, № 3.

EXPLORATIONS 28 the end o f the se ism ic stream er the re is PartnerP last 800L ta il buoy equ ipped w ith a flashing beacon, a radar re fle c to r and a GNSS receiver. The cluste r composed o f 4 G.GUN II a irguns w ith volume of 150 - 40 cub ic inches each is used as elastic wave source. These a irguns are advanced in th e ir class due to high e ffic ien cy in the heaviest cond itions. There is also an a lterna tive source available which comp rises 4 SleeveGun a irguns w ith 40 cub ic inches each. Au tom a tic con tro l and gun w ork synchron ization is pe rform ed by B igShot co n tro lle r which has tim ing reso lu tion of 0 . 1 ms. Additiona lly, the airgun co n tro lle r receives data on the a irgun c lus te r deepening. In o rde r to pack a irguns by air up to p ressure of 2 0 0 0 psi, the high p ressure com p resso r o f 2ВМ -5 221 type produced by the K rasnodar Compressor Plant, Russia, is used. RESULTS Seism ic data in te rp re ta tion is pe rfo rm ed w ith the use o f Kingdom so ftware. For more convenien t ranging of anomalous zones, the basic re fle cting horizons were ou tlined in the study section. A deta iled se ism ic section analysis showed presence of a large number of amp litude anomalies w ith d iffe ren t th icknesses and sizes w ithin the lim its o f the outlined se ism ic zones. A maximum d rilling ope ra tion risk relates to the presence of amp litude anomalies on se ism ic sections, supposedly, being confined to gas-sa tu ra ted deposits and fau lts which, apparently, serve as gas m igration channels up the section . For analysis and iden tifica tion of anomalous zones, we used the fo llow ing fa cto rs : very high re fle c tion am p litudes (more than 1 0 tim es as high as mean lateral value), high re fle c tion am p litudes (more than 5 tim es as high as mean lateral value), re flection phase inversion (po la rity change), “ dow nw a rp ing ” of events under anomaly due to ve lo c ity value reductions (“ve lo c ity e ffe c t” ), sharp reductions of lateral am p litudes not connected w ith fau lts, abso rp tion of high frequen c ie s under anomalies, high values o f AVO -attribute - p rodu c t o f in te rcep t and g radient, amp litude a ttenuation under anomaly, con finem en t of anomalies to weakened zones (includ ing fa u lt systems). Aggrega te o f all the above ­ sta ted fa c to rs shows th a t there is a conside rab le gas con ten t of deposits in the upper part of the section . Anomalous zones are mainly characte rized by a subhorizon tal lateral fo rm as well as small th ickness. W e igh t value was de te rm ined fo r each fa c to r. Estimation was made a cco rd in g to te n -p o in t scale. A fte r ranging o f all com ponen ts due to a com b ina tion of c o n trib u tio n s of each, from fa c to rs one com posed a c lass ifica tion o f am p litude anom a lies by deg ree of risk fo r d rillin g ope ra tion s. In teg ra ted app ra isa l ra tio fo r deg ree o f risk was de te rm ined on the base o f am oun t o f all com ponen ts . Eventually, the fo llow ing cla ss ifica tion was suggested : m ino r - 0 ; low - 1-24; m iddle - 25 -48 ; and high - 4 9 -72 ( F ig . 4 ). Transformation of the time scale into the depth scale was carried out by means of RMS -velocities sections transfe rred a fte r a field data processing stage. Depth map construction was carried out through gridd ing of anomalous zone correla tion results. 2D data interpolation to o k place by least square method in box of 2 0 0 x 2 0 0 m and a smoothing iteration was applied in order to smooth a h igh-frequency component. By delineation results of all high-amplitude areas, a composite map of risks was constructed on which a color gamma corresponds to the degree of risk while conducting drilling operations. Analysis of the above-mentioned seismic data allows determ ining main geologic-geophysical factors defining conditions fo r upper interval penetration and planned well construction. Subsequent to the results of contouring of areas w ith anomalously high amplitudes the risks have been summarized and mapped, and the scale of colors correspond to the drilling risk level. H ighlighted zones of amplitude anomalies have d iffe ren t forms, thicknesses and distribu tion. The follow ing main varieties are distinguished: 1 ) zones with seism ic recording of lenticular shape; 2 ) amplitude anomaly zones of sub-ho rizonta l fo rm s along bedding in the section confined to faults tha t can be connected w ith gas m igration along the fau lt surface and gas saturation of fau lt-ang le deposits. Thus, areas without faults and also areas with a minimum number of high amplitude anomalous zones are recommended to be referred to the most favorable zone fo r arrangement of borehole facilities. CONCLUSION Results of recent works with usage of high-resolution seism ic technology demonstrate its high efficiency and informative value fo r a detailed partition of the upper section fo r the purpose of detection of gas “ lenses” and gas-hydrate deposits. MURMANSK MILE • 3-2016