Regularities of conventional and unconventional gas accumulation in the aspect of hydrogeological and catagenetical zonality (on the example of Dnieper-Donets trough)

Abstract

The conditions of conventional and unconventional gas accumulation in different hydrogeological and catagenetic zones have been examined. Distribution of deep zones of combined unconventional gas accumulation in thermodehydratational hydrogeological zone has been shown. This zone is formed by overlying of shales, sandstones, limestones and coals whose stratigraphic age varies from Low Carbon to the top of Middle Carbon. The rocks are transformed in gradation MK₃ of mezocatagenesis and form an extensive tight reservoir. The depth of its bedding increases from 2,5-3,0 km on South-East to 5,0-5,5 km on North-West. The thickness of this zone varies from 300-400 to 800-900m. This complex represents “catagenetical fluidproof” that controls the zone of abnormal high pressures and at the same time it serves as practically waterless tight reservoir which contains combined unconventional gas resources. The objects for assimilation of combined unconventional gas at Dnieper-Donets Trough have been proposed.