Thermal Evolution Of The Shuntuoguole Low Uplift And The Surrounding Areas In Tarim Basin

The Ordovician carbonate intervals of Shuntuoguole low-uplift in the Tarim basin are hot spots for hydrocarbon exploration in recent years,which is characterized by a deep burial depth(6000m?8000m)and high burial temperature(150??200?).However,the lack of systematic temperature research and material for traditional thermal proxies significantly hindered the thermal history understanding and the petroleum exploration.In this study,the present geothermal field characteristics and main controlling factors of the Shuntuoguole low-uplift in Tarim Basin are analyzed based on various temperature data and the thermal conductivity.Combined with various geothermometers(ZHe,Ro and clumped isotope)and thermal dynamic model of different geothermometer,the thermal histories of Ordovician carbonate intervals in Tarim Basin are reconstructed.On the basis of reconstructed sedimentary burial history and thermal history,the influence of thermal evolution on temperature in the Permian and on hydrocarbon accumulation in deep strata in the Shuntuoguole low uplift of Tarim Basin are analyzed.The research shows that the geothermal gradient in Shuntuoguole low-uplift is generally between 19.4?/km and 28.5?/km,and the geothermal heat flow is 34.3m W/m~2 to 59.2 m W/m~2 with an average of 45.4 m W/m~2,which belongs to the high geothermal gradient and heat flow in Tarim Basin.The temperature gradually increases from Shunbei to Shunnan area,but the temperature near SN4 fault zone is about 10??20?higher than that of the surrounding rock.This thermal disturbances is possibly caused by hydrothermal fluids passing through the fracture system from the deep strata to the Ordovician strata.There are three phases of heat flow evolution in the Shuntuoguole low-uplift:(1)The gradual cooling stage during Ordovician-carboniferous.The heat flow is gradually decreasing during this period;(2)Rapidly raised stage in the early Permian period.The heat flow in Shunbei and Shuntuo area are raised rapidly during this period and the maximum is 51 m W/m~2?65 m W/m~2,but the SN3 well in Shunnan area increased slightly and the heat flow values of other single wells were still relatively stable.(3)The decline stage since Middle Permian.The tectonic activity is relatively stable and the geothermal heat flow is gradually reduced during this period,but the heat flow in Shunnan area is higher than the Shunbei and Shuntuo areas.By setting different thermal history paths for typical single wells in the Shuntuoguole area,the upper limit of the maximum temperature is determined to be 170°C?190°C.In addition,the abnormal high temperature of the Permian may be the result of the combination of erosion and magmatic activity events.The Permian geothermal gradient in the Shuntuoguole area ranges from26.75°C/km to 46.28°C/km,showing a trend of high northeast and low southeast.The spatial variation of the geothermal gradient suggests that the magma activity center may be located near the Tabei area,and the thermal response caused by magmatic activity may terminate near the SN3 well.Controlling by the thermal evolution,the dissolution of the Middle-Lower Ordovician carbonate reservoirs in the Shuntuoguole area is earlier than the generation of hydrocarbons.The improvement of reservoir properties provides for the filling of oil and gas in the later period,and the time of crude oil cracking gas and the hydrocarbon accumulation time are relatively late,which is beneficial to the preservation of giant oil and gas reservoirs.