南海盆地地热地质条件和资源形成因素

Geothermal geological conditions and resource formation factors in the South China Sea Basin

南海是世界上第三大边缘海,也是中国最大的边缘海。复杂的构造应力和演化过程成就了该区域优质的地热背景条件。本文以南海海域大地热流、热储、流体地热数据为依据,基于南中国海的热历史、热状态以及流体地热特征认识基础上,分析研究莺-琼盆地11个地层水样和13件样品岩石热物性参数,从盆地热演化、岩石圈热结构、构造背景、热源、热储、盖层条件等方面探讨了南海盆地地热地质条件,对地热资源形成进行了分析。认为其是5 Ma以来活动构造最为活跃的地带,发育海山、高压流体底辟、气烟囱等,是热事件最活跃区;地幔热流与地表热流之比为0.59,具有“冷壳热幔”的岩石圈热结构特征;洋中脊、红河断裂等深大断裂带、以伸展构造为主的断块、底辟核心影响区等,提供了深部热物质上涌“热通道”,造成现今地温异常;以莺-琼盆地为例,按热储区域封盖组合特点,由浅层乐东组到深层崖城组,划分了浅层中-低温地热系统,中深层高温地热系统、深层超温地热系统。南中国海地热资源的勘探和利用研究尚处于起步阶段,结合海洋地热开发利用现状以及对比南海地热资源优势,从技术、经济角度探讨海洋地热资源开发利用发展方向。

The complex tectonic stress and evolution process of Hainan Sea,the largest marginal sea in China,results in high quality geothermal background conditions.Based on the data of terrestrial heat flow,heat storage,fluid geothermal data,thermal history,thermal state and fluid geothermal characteristics in the South China Sea,this paper analyzes and studies the thermal property parameters of 11 formation water samples and 13 rock samples in Yingqiong Basin.The geothermal geological conditions of the South China Sea Basin are discussed from the aspects of basin thermal evolution,lithospheric thermal structure,tectonic setting,heat source,heat storage and cover conditions,in an attempt to analyze the formation of geothermal resources in the South China Sea.The results show that the study area has been the most active tectonic zone since 5 Ma,characterized by the formation of seamounts,high-pressure fluid diapirs and gas chimneys,and it is the most active area of thermal events.The ratio of mantle heat flow to surface heat flow is 0.59,which shows the characteristic thermal structure of“cold crust and hot mantle”.Deep large fault zones such as mid-ocean ridge,Honghe Fault,fault block dominated by extensional structure,diapir core influence area,etc.,provided deep hot material upwelling“hot channel”and resulted in the present geothermal anomaly.In Yingqiong Basin,such geothermal systems as shallow middle-low temperature geothermal system,middle-deep high temperature geothermal system and deep ultra-warm geothermal system can be divided according to the characteristics of capping assemblages from shallow Ledong Formation to deep Yacheng Formation in heat storage areas.The exploration and utilization of geothermal resources in the South China Sea is still in the initial stage,so it is necessary to make use of the advantages of geothermal resources in the South China Sea and to explore the development direction of marine geothermal resources from the technical and economic perspectives.