Heat production rate and heat flow contribution of the sedimentary formation in Junggar Basin, northwest China

As an important part of the terrestrial heat flow, radioactive heat flow production of sedimentary formation can warm the deep and ultra-deep source rocks and promote their maturity evolution effectively in the 'cold' basins in western China which are characterized by low geothermal gradient and low terrestrial heat flow. 6, 120 heat production rates of sedimentary formation in 16 boreholes among six tectonic units in Junggar Basin were acquired using different empirical relationships between natural gamma ray (GR) and heat production rate (A). By comparison with the measured heat production rates, the applicable GR-A empirical relationship to the study area was determined. Then, the heat production rate columns of the sedimentary formation in Junggar Basin were established and the heat flow contribution of the sediments was calculated. Finally, as an example, its warming effect of Well Pc2 was calculated quantitatively. The results showed that the average heat production rate of the sediments in Junggar Basin was 1. 179 +/- 0. 339 mu W . m(-3) and it decreased gradually as the formation age became older. The Quaternary formation was with the maximum heat production rate while the Carboniferous formation minimum. The average heat flow contribution of the sediments was 7. 9 +/- 14. 9 mW . m(-2), which was approximately 29. 2% of average crustal heat flow and 19. 6% of average terrestrial heat flow. The heat flow contribution of sediments was consistent with the thickness of sediments and showed the following characteristics. (1)Relatively high heat flow contribution of sediments was confined to the Central Depression. (2) Southern Depression varied dramatically on heat flow contribution of the sediments. (3) The Luliang Uplift and Western Uplift were characterized by lower heat flow contribution of the sediments. (4) The lowest heat flow of sediments occurred in the Eastern Uplift and Wulungu Depression. The heat flow contribution of sediments can warm effectively the deep and ultra-deep source rocks in Junggar Basin and promote maturity evolution of the organic matter. For example, the temperature in the bottom of J(1)s source rock (5300 m) in Well Pc2 was 7. 3 degrees C higher in the condition of considering the heat production of sediments. Obviously, it was very significant to the hydrocarbon resource evaluation and exploration targets optimization in Junggar Basin which was characterized by low geothermal gradient and deep reservoirs.