冀鲁豫三省交界处临清坳陷大名次凹陷地热系统成因模式及开发潜力

Genetic mechanism of geothermal system in Daming Sag,Linqing Depression in the junction of Hebei,Shandong and Henan Provinces and its exploration potential

【研究目的】建立地热系统的成因模式对地热田地热资源量评价以及后期有利区带的优选有着重要指导作用。大名次凹陷为渤海湾盆地临清坳陷馆陶凸起南端的一个次一级构造单元,其馆陶组砂岩热储可以构成一套完整的地热系统。【研究方法】本文结合前人研究成果和区内地热钻井资料,通过对临清坳陷大名次凹陷地热系统“源、储、通、盖”主要地质因素分析研究,建立了研究区地热系统的概念模型,并在此基础上开展了地热资源量评价。【研究结果】馆陶组热储层在区内分布均一,底板埋深在1550~2000 m,储层厚度在268~324 m,孔隙度介于14%~32%,储厚比最高可达70%。区内钻遇至馆陶组的地热井,地热水井口水温多在54~60℃,水化学类型以Cl·SO_(4)-Na为主。上部沉积的第四系和明化镇组,地温梯度在22~60℃/km,构成了良好的盖层。地热系统热源主要来自于新生代断陷盆地背景下的高大地热流值,约52~57 mW/m^(2),南部临漳—大名断裂和东部冠县断裂为其深部热流向上运输的有利通道。热储整体接受来自西部太行山和东部鲁西南隆起的大气降水补给,经深部热传导和局部热对流增温后,富集于热储之中。【结论】馆陶组砂岩地热系统资源量超过127.42×10^(8)GJ,每年可开采地热资源量为31.86×10^(6)GJ,折合标煤1.09×10^(6)t。年开采地热资源量可满足超3.14×10^(7)m^(2)的供暖面积,开发潜能较大。

This paper is the result of geothermal survey engineering.[Objective]Building genetic model of the geothermal system plays an important guiding role in the evaluation of the geothermal resources of the geothermal field and the later selection of favorable zones.Daming Sag is a secondary structural unit at the southern of Guantao Uplift in Linqing Sag,Bohai Bay Basin.The sandstone thermal reservoir of Guantao Formation can form a complete geothermal system.[Methods]Combining previous research results and regional geothermal drilling data,through analysis and research on the main geological factors of the“source,reservoir,migration,and cover”,the conceptual model of the geothermal system was established in Daming Sag,Linqing Depression.On this basis,a evaluation of geothermal resources was carried out.[Results]The thermal reservoirs of the Guantao Formation are uniformly distributed in the area,the floor depth is between 1550-2000 m,the thickness of the reservoir is between 268-324m,the porosity is between 14%-32%,and the reservoir-thickness ratio can reach up to 70%.The geothermal wells drilled into the Guantao Formation in the area,its water temperature is about 54-60℃,and the water chemistry type is mainly Cl×SO^(4)-Na.The upper Quaternary and Minghuazhen Formation strata have a geothermal gradient between 22-60℃/km,forming a good cap layer.The heat source comes from the high geothermal value background of the Cenozoic rift basin,about 52-57 mW/m2.The Linzhang-Daming fault in the south and the Guanxian fault in the east are favorable channels for the upward transportation of deep heat.The geothermal system receives the atmospheric precipitation replenishment from the Taihang Mountains in the west and the southwestern Luxinan uplift in the east.After being warmed by deep heat conduction and local heat convection,it is enriched in the reservoir.[Conclusions]The evaluation results of the geothermal resources in the Damingci Depression show that the sandstone geothermal system resources of the Guantao Formation are more than 127.42×10^(8)GJ,the annual geothermal resources that can be exploited are 31.86×10^(6)GJ equivalent to 1.09×10^(6)t of standard coal.The annual exploitation of geothermal resources can meet the heating area over 3.14×10^(7)m^(2),and the development potential is great.