Analysis Of Heat Flow,Heat Generation Rate And Thermal Structure In The South Yellow Sea

Geothermal flow,geothermal gradient,thermal conductivity and heat generation rate of rocks are the basic geothermal parameters,which provide geothermal background and basic parameters for the study of geodynamic evolution and hydrocarbon generation.In this paper,the natural gamma data of 9196 points in 8 wells,including well ZC1-2-1,well ZC7-2-1,well CZ24-1-1,well WX4-2-1,well WX5-ST1,well WX13-3-1,well CZ35-2-1 and well CSDP-2,are collected.Through the weighted average of the heat generation rate of different groups of strata,the average heat generation rate of strata in different times is calculated respectively.At the same time,the average heat generation rate of different formation is calculated by weighted average processing,and the results show that the heat generation rate of formation in the South Yellow Sea increases with the increase of depth(age).In this paper,based on the relationship between the Curie Point Depth(CDP)and the geothermal flow and the geothermal gradient,the CDP of 39 sites in the South Yellow Sea is collected,and the average heat flow value of the South Yellow Sea is 67.04 m W/m2,slightly higher than the global heat flow value of 65 m W/m2;the average geothermal gradient is 29.30 ?/km,slightly lower than the average geothermal gradient(30 ?/km)of the adjacent Subei basin.Taking well ZC1-2-1 in the northern depression of the South Yellow Sea as an example,this paper calculates the crustal structure and thermal structure model of the study area.According to the relationship between P-wave velocity and crustal structure,the total thickness of the crust in the area near the well site is 32.5 Km,in which the thickness of sedimentary layer is 3.4 km,that of the upper crust(excluding sedimentary layer)is 8.6km,that of the middle crust is 4km,and that of the lower crust is 16.5 km.According to the weighted average heat generation rate of each formation,the average heat generation rate of sedimentary layer is 0.88 ?W/m3;according to the relationship between P wave velocity and heat generation rate,the average heat generation rate of upper crust(excluding sedimentary layer)is 1.4 ?W/m3;the average heat generation rate of middle crust is 0.54 ?W/m3;the average heat generation rate of lower crust is 0.23 ?W/m3.Finally,based on the above calculation results,according to the relationship between heat generation rate and heat production,the heat production of sedimentary cover,upper crust(excluding the part of sedimentary layer),middle crust and lower crust in the South Yellow Sea area are calculated as 5.85 m W/m2,12.04 m W/m2,2.16 m W/m2 and 3.8 m W/m2 respectively,so the total heat production of the crust(including the sedimentary cover)is 23.85 m W/m2,accounting for 36.6% of the surface heat flow.The heat flow produced by mantle is 41.15 m W/m2,and the heat flow ratio of crust to mantle is 0.58,which is characterized by "cold crust and hot mantle".