Zone forecast of oil and gas content of North-Kara basin Печать E-mail

State Company "SEVMORGEO", Russia

North-Kara shelf remains the least investigated part of the West-Arctic continental surburb both in geological, and in petroliferous relations, hi the general structural plan it consists of two large sublatitude zones.

Southern it is expressed in a structure of a sedimentary cover by extensive negative structures of 1 order with depths of plunge of the folded basement up to 12-13 kims in North-Novozemelskaya and up to 20-22 kms in North-Kara depressions divided by a narrow contrast excess of the basement of meridianal direction, appropriate to Uedineniya saddle, hi the north the made active regional shelf raising dismembered by zones of the recent movements on a number of separate blocks is marked.

For this structural zone typically general reduction of volumes of the sedimentary cover reaching 8-9 kms only in separate blocks and prevailing depths of the basement from 2 up to 6 km. The marked feature, apparently, can cause the certain phase zoning in distribution of hydrocarbon (HC) contents. In the depressions of a southern zone described by the maximal thickness of sedimentary cover and, accordingly, in the most significant volumes of source rocks, covered with intensive processes of oil generation and, in the greater measure, gas generation, in view of that the most part of productive stratas was on depths over 4-6 kms (the main zone of gas formation), obviously, gas and gas condensate will prevail.

Generation of enormous volumes of НС-gases in the central parts of depressions and their superseding influence promoted redistribution of earlier formed liquid HC pools. Constant migration of the gases, increased in result of recent movement, have resulted in mass emigration of petroleum from source rocks, and also to its replacement together with oils of earlier formed pools aside the raised structures of a southern zone, but with a general direction of HC migratory stream to margin parts of basin - in northern zone of uplifts. And, change of HC phase component for different zones will be proportional to the sedimentary cover thicknesses advanced in their limits - aside increases of HC densities in zones with as much as possible reduced section of sedimentary cover complex.

For submerged parts of Barents-North-Kara basin the moderate mode recent movements and inheritance of basement structures in the modern structural plan that is the important positive factor influencing on oil and gas content is characteristic, is especial for formation and safety НС-gases which here should have a predominating role. The important factor, obviously, location in this part of basin of the reliable cap rocks connected to Upper Jurassic - Lower Cretaceous thick clay formation is also. Their local distribution within the limits of northern uplift areas, alongside with wide spread of disjunctive, considerably reduces probability of safety of large gas pools. It defines their mainly petroleum specialization. Most probably here location of oil pools in lithologic or tectonic traps. The zoning of other sort consisting in gradual change of a role of the basic complexes of sediments in section of a sedimentary cover is established in a direction to northeast pails of basin. For southern and western parts managing role of mesozoic sediments where their capacity reaches 3-6 kms is characteristic. Aside Severnaya Zemlya value of a paleozoic complex appreciably grows by way of HC generation and accumulation.

To the factors rendering negative influence on formation and safety of commercial HC pools, concerns active recent movements a mode within the limits of uplift. But there is also a positive moment in abundance of disjunctives - activization of migratory processes in a subvertical direction and formation of tectonic traps. The researches which have been carried out by authors on many islands of archipelago FJL, it is not established attributes of massive HC migration with formation large superficial bitumen shows, that it is usually typical of areas where processes of HC pools destruction are advanced. The conclusion from here follows, that in the investigated area, at least, in zones of an island land, direct geochemical factors of oil and gas content are established and, at the same time, there are no certificates on wide spread of active destruction processes of oil pools.

By the majority before the executed estimations of a zone of regional raisings as the perspective grounds were not considered, though the general structural - tectonic and geologic-geochemical preconditions allow to hope, that prospects of them are essential. To this those have also, insignificant in scales of region, the geochemical data which are received by results of researches of in areas of east board of St.Anna trench and Vise and Ushakov uplifts. These structures can be referred to perspective today. Necessity of performance of a complex of geophysical researches on Sevmorgeo profiles 3-AR & 4-AR and realization of bottom sediments resampling in cooperation with statement of parametrical drilling on Vise island is obvious.

For North-Kara basin, in view of the new data about oil and gas content of northern regional uplifts zones, the area of the perspective grounds can achieve 220 thousand sq.kms. At concentration of resources at 30-40 thousand t/sq.kms their total volume will make 6,6 - 8,8 bill.t o.e. Prospects of liquid HC reserves increase in the greater degree are connected to northern territories described by wide spread of an island land that defines their prime value at development.



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