Role of elision water exchange in formation of the Yamalo-Kara depression hydrodynamic field

Abstract

The unique material has been compiled on the hydrodynamics of oil and gas deposits of the Yamalo-Kara Depression for the first time in the last 30 years. The main feature of the region is the wide development of abnormally high formation pressures (Ka to 2.21) in both Jurassic and Lower Cretaceous horizons. Studying the filtration-capacitive properties and hydrodynamic characteristics of the Jurassic-Cretaceous reservoirs allows to established the predominate role of the elision water exchange in the formation of the modern hydrodynamic structure. At the depth of about 2–2.5 km elisional lithostatic system begins to acquire the features of elisional thermo-dehydration system. The extensive zones of piezomaxima (Bolshekhetskaya and Karskaya megasyneclise) at the present stage of development of the water-pressure basin system became internal areas of water pressure (supply) with a maximum degree of hydrogeological closeness. The vast zones of piezomaxima (the Bolshekhetskaya and Karskaya megasyneclises) became the inner regions of water pressuring (feeding) with the maximal degree of hydrogeological closeness of the interior at the current stage of the development of the water-pressure system in the basin. The areas of piezominima extending along the main sites of oil and gas generation are related to the largest zones of oil and gas accumulation (Vankoro-Suzunskaya, Bovanenkovskaya, Urengoyskaya and others). Currently, two types of natural water-pressure systems has been established in the region under investigation: elision in the inner regions (dominating within the Yamalo-Kara depression) and infiltration — in the basin margins of the West Siberian sedimentary basin.