Published November 2009
Geological methods of system zoning of complex oil and gas regions with use of the retrospective analysis of evolution sedimentary - rock basins
S.A.AliyevaThe main difference complex regions consist following. They have undergone some stages of a geodynamic cycle of evolution of a lithosphere and consequently have complex history of tectonic development that has led to presence of several structural floors in a section of rocks composing them as a result of numerous reorganizations of the tectonic plan. Principal causes of such structural reorganizations are moving lithosphere plates as a result of which there are rifting zones, then - subduction zones and at collision of continental plates - large zones of an orogenesis and so on. As a rule, complex regions are usually dated for folded and transitive territories, however, in some cases such complex regions take place and on marginal of platform territories, in zones of a joint of platforms of uneven-age consolidation where the salt dome tectonics and reef-building uplifts (bioherms) are developed. As is known, the tectonic mode, finally, defines development in a section and on the area of sedimentary-rock basins of oil and gas producing rocks, ways of migration of oil and gas, presence of collectors, covers of oil-bearing stratas and traps - that is all those factors at which favorable combination in time and space there are necessary conditions for generation, migration, accumulation and preservation of oil and gas deposits. The modern tectonic structure of large sedimentary-rock basin, especially in complex regions grows out long, often multistage evolution. It is frequently not only changing configuration of such basin, but also result in his partition on some large paleobasins, or, on the contrary, to merge of some less large paleobasins in a uniform large (largest) paleobasin, or result in inversion of such paleobasin. All it substantially complicates carrying out of oil and gas geological zoning and result in various interpretation of belonging of those or other territories to large parts of system of zoning. Therefore, in our opinion, one of ways of objective oil and gas geological zoning of complex regions is obligatory use of the retrospective analysis of sedimentary-rock basins in which regional oil and gas bearing complexes were formed in addition to the tectonic analysis. The primary goal of such analysis is, in the first, delimitation of sedimentary-rock basins, which existed during formation regional oil and gas complexes, with which are connected (or are predicted)deposits of oil and gas. And in the second is to define, whether existed in considered region, during formation of regional oil and gas bearing complexes some such isolated paleobasins, or here there was a uniform paleobasin. Considering importance of the above-stated analysis of evolution of large (largest) oil and gas sedimentary-rock basins at oil and gas geological zoning, we had been essentially added definitions of large parts of this system: Oil and gas province is significant in the sizes and sedimentary filling isolated oil and gas territory dated to regional or group of adjacent large tectonic elements which during formation of all or parts of regional oil and gas bearing complexes represented uniform sedimentary-rock basin. The oil and gas province is limited either the unpromising or small prospective grounds, either large faults and (or) sharp change of a structure of a sedimentary cover. Oil and gas sub province is the large oil and gas part of an oil and gas province, including not less of two oil and gas regions which at a stage of formation of ancient or young regional oil and gas bearing complexes represented independent sedimentary-rock basin, and later, before formation of young regional complexes or has incorporated to other basin in uniform oil and gas province, or after formation of ancient regional oil and gas bearing complexes was allocated from uniform largest sedimentary-rock basin in large independent sedimentary-rock basin. Independent oil and gas region is a large oil and gas (prospective oil and gas) part of tectonic region which during formation of regional oil and gas bearing complexes (or their any part) represented uniform largest sedimentary-rock basin, and then as a result of any reasons in its other territory these complexes have been destroyed, either have undergone to an intensive metamorphism or have been deduced in an aconservation zone. On our belief, use of the above-stated methodology along with an estimation of tectonic and other criteria of an oil and gas bearing will allow to allocate more precisely large parts of system of oil and gas geological zoning.
