反射地震剖面揭示容城凸起基岩面和断裂结构及其对地热成因的启示

Bedrock surface and fault structures in the Rongcheng uplift revealed from reflectionseismic profiles and their implications for the geothermal origin

容城凸起是华北地区地热资源富集区域之一,探测容城凸起基岩面的精细结构、埋深和断裂,对理解该区地热资源的分布和富集以及地热资源的勘查与开发具有重要意义。本文基于中国地质科学院2018年在容城凸起采集的SN向反射地震剖面数据,通过对反射数据精细处理,获得容城凸起4 km以浅的高精度几何结构,经地热孔资料标定后开展解释。主要获得以下4点认识:容城凸起基岩面以上新生代沉积地层呈近水平层状分布,这些近水平地层对容城地热田起到保温盖层作用;容城凸起基岩面埋深在700~3000 m之间,其凸起中心部位变化相对平缓,向周边迅速加深到3000 m左右;牛南断裂和容东断裂在深部延伸交汇,与其他中、小型断裂组成的断裂系统为水和热的传导提供了通道和空间;基岩面凸起的几何结构有利于热流在凸起下方汇聚。

The Rongcheng uplift in North China boasts abundant geothermal resources.Research indicates that the Rongcheng uplift exhibits significantly different physical properties between the bedrock surface and the overlying Cenozoic strata.Moreover,the bedrock surface serves as the primary top boundary of the geothermal reservoir in the Wumishan Formation.Investigating the fine-scale structures,burial depths,and faults of the bedrock surface in the Rongcheng uplift holds critical significance for understanding the distribution and enrichment of geothermal resources in the area and guiding their exploration and production.Through elaborative processing of the north-south reflection seismic profile data of the Rongcheng uplift,collected by the Chinese Academy of Geological Sciences in 2018,this study obtained the high-precision geometric structure of the Rongcheng uplift within a depth of 4 km.The geometric structure was calibrated using geothermal borehole data before interpretation.Key findings are as follows:(1)The Cenozoic sedimentary strata overlying the bedrock surface of the Rongcheng uplift exhibit a nearly horizontal layered distribution,serving as cap rocks of the Rongcheng geothermal field;(2)The bedrock surface of the Rongcheng uplift manifests burial depths ranging from 700 to 3000 m,with gentle changes in the central portion,and rapidly deepening to around 3000 m towards the periphery;(3)The Niunan and Rongdong faults converge in the deep part,constituting a fault system along with other medium and small faults,thus facilitating the conduction of water and heat;(4)The geometric structure of the Rongcheng uplift on the bedrock surface contributes to the convergence of heat flow beneath the uplift.