On The Results of Investigation of the Causes of Anomaly High Formation Pressure at the Fields of the South-Eastern Part of the Bukharo-Khiva Region

Abstract

According to the studies of A.Kh. Nugmanov, the migration of oil along the bedding of sediments continued until the Amudarya sedimentary basin subsided - until the end of the Paleogene. During this time, gaseous hydrocarbons emigrated into the water reservoir and dissolved in the formation waters, tending to completely saturate them. The degree of saturation of waters with gases by the end of the Paleogene in the focus of subsidence could reach the limit value, when the reservoir pressure (?pl) and the saturation pressure (?sat) of dissolved gases became equal. When equal Rpl and Rus. Dissolved gases are released into the free state. At the same time, the regional uplift of the Turonian plate that occurred at the end of the Paleogene caused the regression of the sea and erosion of sediments, which led to a decrease in Psh in aquifers and its alignment with Psa. For this reason, in a short geological time, almost the entire area of the Amu Darya sedimentary basin began to release gaseous hydrocarbons from formation waters and their migration. As a result, the previously formed oil deposits were at the margins of the basin and beyond - the Jurassic carbonate stratum became predominantly gas-bearing. Gas migration continued while erosion proceeded. Simultaneously with the regional uplift of the sedimentary basin at the end of the Oligocene, the emigration of hydrocarbons from oil and gas source rocks is interrupted. Regional uplift, which changed to subsidence at the beginning of the Middle Miocene, was accompanied by the accumulation of sediments. This led to an increase in Pm and a breakthrough in the release of water-dissolved gases [5: 14].