琼东南盆地疑似泥底辟与天然气水合物成矿成藏关系初探

根据琼东南盆地构造沉积特征，区域地球物理调查与油气勘探成果，分析研究了该区疑似泥底辟发育与分布特征及其与天然气水合物富集成矿成藏之间的关系。结果表明：疑似泥底辟与天然气水合物均主要展布于盆地凸起和凹陷构造单元过渡带或沉积凹陷中心等区域，二者分布位置上具有一定的重叠性，而沉积有机质生成的浅层生物气及亚生物气与深部热解气等，均可通过泥底辟及气烟囱或断层裂隙构成的气源供给输导系统，在深水区高压低温稳定域富集成矿形成天然气水合物，表明泥底辟及气烟囱等构成的气源供给运聚通道系统与天然气水合物成藏具有一定的时空耦合配置关系。预测研究区存在“生物气-亚生物气自源自生自储原地成矿成藏、热解气他源断层裂隙输导下生上储异地成矿成藏、热解气他源泥底辟及气烟囱输导下生上储异地成矿成藏”3种类型天然气水合物成矿成藏模式。

Preliminary Study of the Relationship between the Suspected Mud Diapir and Natural Gas Hydrate in the Qiongdongnan Basin,Northern South China Sea

Based on the tectonic and deposition characteristics,regional geophysical survey as well as hydrocarbon exploration of Qiongdongnan Basin,the development and evolution,and distribution features of the suspected mud diapir,the relationship between the suspected mud diapir and natural gas-hydrate are studied.The results show that the suspected mud diapir,the gas chimney and natural gas-hydrate are mainly distributed in the conjunction area between uplifts and sags,as well as the central of sags,what's more,there are overlapping area in geography between suspected mud diapir and natural gas-hydrate.Biogenic gas and sub-biogenic gas derived from organic matter in shallow layer,as well as thermal gas derived from organic matter in deep strata accumulate in the temperature and pressure stable zone through the gas supply and migration and accumulation system which comprised the suspected mud diapir,the gas chimney,or faults and fractures,and natural gas-hydrate come into being,which show that gas supply system that is composed of suspected mud diapir and gas chimney has space-time coupling configuration relationship with accumulation of natural gas-hydrate.It is forecast that there are three accumulation models of natural gas-hydrate,including self-sourced diffusion biogenic gas and sub-biogenic gas accumulate in place by way of “self-generation and self-bearing”,foreign sourced thermal gas accumulate offsite through faults and fractures by way of “lower-generation and upper storage”,foreign sourced thermal gas accumulate in offsite place through mud diapir and gas chimney by way of “lower-generation and upper storage”.