渤海湾盆地冀中坳陷现今地热特征

渤海湾盆地冀中坳陷是我国最典型的潜山油气藏富集区.本文借助117口钻井地层测温资料和45块实测岩石热导率数据系统研究了冀中坳陷现今地温梯度、大地热流、热岩石圈厚度、岩石圈热结构等地热特征参数.研究表明,冀中坳陷0~3000m统一深度现今地温梯度为20.8~41.0℃·km-1,平均值为31.6℃·km-1,比未校正值减小1~3℃·km-1;现今大地热流介于48.7~79.7mW·m-2,平均值为59.2mW·m-2.平面上,冀中坳陷现今地温梯度和热流由西向东(从盆地边缘向内部)逐渐增大,并且凸起区地温梯度和热流相对较高,而凹陷区则偏低,与基底地形起伏具有很好的对应关系.同时,冀中坳陷腹部高热流凸起区广泛分布地热田.冀中坳陷现今热岩石圈厚度为98~109km,其岩石圈热结构为一典型的"冷壳热幔"型.本研究不仅对冀中坳陷油气勘探与地热能开发具有重要的指导意义,而且为深部岩石圈研究(华北克拉通破坏科学问题)提供了新依据.

Present-day geothermal regime of the Jizhong depression in Bohai Bay basin,East China

As a second major tectonic unit of the Bohai Bay basin,the Jizhong depression is a very typical area in China with enrichment of buried-hill hydrocarbon reservoirs.Based on 117 borehole temperature data and 45 measured thermal conductivity data,we studied present-day geothermal characteristics of the Jizhong depression systematically such as geothermal gradient,terrestrial heat flow,thermal lithosphere thickness and lithospheric thermal structure. The results show that the present-day geothermal gradients at depths 0~3000 m in this region range from 20.8℃·km^-1 to 41.0℃·km^-1 with a mean of 31.6℃·km^-1, lower 1~3℃·km^-1 than uncorrected value. The heat flow varies between 48.7~79.7 mW·m^-2 with an average of 59.2 mW·m^-2. Present-day geothermal gradients and heat flow of this depression gradually increase from west(basin margin) to east(basin interior) horizontally. These values in sub-uplift areas of the Jizhong depression are usually higher than those of the sub-depression regions,and their variations correspond to the basement relief very well. Meanwhile,the uplift areas with high heat flow in the central Jizhong depression host amounts of geothermal fields. In addition,we calculated the thickness of present-day thermal lithosphere of study area to be 98~109 km,and its lithospheric thermal structure is a "cold crust and hot mantle" type now. This study has an important guiding significance for hydrocarbon exploration and geothermal energy exploitation in the Jizhong depression,and provides new insights for deep lithosphere research(especially for the scientific problem-North China Craton destruction).