文昌A凹陷地温-地压系统与油气成藏的关系

Geothermal-Geopressure System in the Wenchang A Sag and Its Relationship with Hydrocarbon Accumulation

地温-地压系统(以下简称温压系统)控制油气的生成、运移和聚集,为明确文昌A凹陷温压系统特征及其与油气成藏的关系,基于地温和地压实测数据及声波测井等资料,利用温压系统原理,对珠江口盆地文昌A凹陷的地温场、地压场及温压系统特征进行剖析,从油气的生成、保存及分布角度探讨温压系统与油气成藏的关系。研究表明:文昌A凹陷地温梯度较高,平均为33.8℃/km,有利于有机质的成熟与烃类的生成;泥岩欠压实段集中在珠海组、恩平组,强化了油气的封盖作用;珠江组泥岩不发育异常压力,以毛细管压力封闭为主;凹陷发育高压型复式温压系统,上、下2套温压系统的流体能量差较大,油气以垂向运聚为主,浅部静压型温压系统内部最利于油气富集成藏,恩平组含油气系统是最重要的勘探对象。该研究对珠江口盆地的勘探有一定的指导意义。

Geothermal- geopressure system （temperature-pressure system） may eftctively control generation, mi- gration and accumulation of hydrocarbons. To clarify specific fatures of the temperature-pressure system in Wen- chang A Sag and its relationship with hydrocarbon accumulation, features of geothermal field, geopressure field and temperature-pressure system in Wenchang A Sag of the Pearl River Mouth Basin have been reviewed by using measured geothermal and gcopressure data, together with acoustic logging and other data through principles related to the temperature-pressure system. In this way, correlation between temperature-pressure system and hydrocarbon accumulation can be clarified with regard to generation, preservation and distribution of hydrocarbons. Research re- suits show the Wenchang A Sag has relative high geothermal gradient of 33.8~C/km on average. Such high gradient may facilitate maturing of organic matters and formation of hydrocarbons ; Less compacted mudstone intervals distrib- uted mostly in the Zhuhai Formation and Enping Formation. Such intervals may strengthen the capping capacities o- ver hydrocarbons. Mudstone in the Zhujiang Formation contains no abnormal pressure, instead, the interval is pre- dominantly sealed under capillary pressure ; The sag contain high-pressure composite temperature-pressure system. There are significant differences in energy of fluids contained in the 2 temperatme-pressm-e systems. Hydrocarbons may migrate predominantly in vertical directions. Static temperature-pressure system in shallower formations may provide the most favorable conditions for enrichment and accumulation of hydrocarbons. In addition, hydrocarbon- bearing system in the Enping Formation can be considered as key exploration targets. Relevant research results may provide valuable references for exploration operations in the Pearl River Mouth Basin.