Present-day superdeep thermal regime of the Tabei-Northern Aman area in the Tarim Basin, Northwest China

;.... Exploration shows that the superdeep layers in the Tabei-Northern Aman area of the Tarim Basin are still rich in liquid hydrocarbons. However, the research on its thermal regime related to the phase and preservation of the oil and gas is still few. This situation restricts further oil and gas exploration. This paper combined massive temperature measurement data and a 1-D steady-state heat conduction equation to systematically study the present-day geothermal gradients, terrestrial heat flow, and temperature distribution characteristics of different depths and key strata in the Tabei-Northern Aman area. The present-day geothermal gradients at unified depth of 0 similar to 5000 m range from 16.2 to 25.3 degrees C.km(-1) with a mean of 21.0 +/- 1.4 degrees C.km(-1) . The heat flow varies between 27.4 similar to 44.5 mW.m-2 with an average value of 35.4 +/- 2.5 mW.m(-2). They show that the present-day geothermal field of the Tabei-Northern Aman area is a "cold" thermal background. The formation temperature of 6000 similar to 10000 m superdeep layers increases with increasing burial depth. It has a distribution characteristic of decreasing first and then increasing from north to south and decreasing from east to west on the plane, which is mainly related to the lithospheric thermal structure, basement relief and rock's thermophysical parameters. The present-day formation temperature at the bottom of the Ordovician in the Tabei-Northern Aman area is between 107.0 similar to 171.0 degrees C with an average value of 145.1 degrees C, indicating that the upper reservoirs are generally suitable to the preservation of liquid hydrocarbons. The present-day temperature of the Yuertusi Formation source rocks at the bottom of the Cambrian is between 120.8 similar to 184.7 degrees C with an average value of 155.9 degrees C, which shows a gradual increase from northwest to southeast. The temperature distribution feature is negatively correlated with the density of the Ordovician crude oil and positively correlated with the gas-oil ratio and gas dryness coefficient. This study not only clarifies the characteristics of the superdeep geothermal field in the Tabei-Northern Aman area, but also discusses the relationship between the superdeep geothermal field and the oil and gas geochemical properties of the Lower Paleozoic, which are of great significance to the future hydrocarbon exploration in the superdeep marine carbonate rocks.