文昌A凹陷地温-地压系统与油气成藏的关系

摘要

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 effectively control generation, migration and accumulation of hydrocarbons.To clarify specific features of the temperature-pressure system in Wenchang 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 geopressure 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 results show the Wenchang A Sag has relative high geothermal gradient of 33.8℃/km on average.Such high gradient may facilitate maturing of organic matters and formation of hydrocarbons;Less compacted mudstone intervals distributed mostly in the Zhuhai Formation and Enping Formation.Such intervals may strengthen the capping capacities over hydrocarbons.Mudstone in the Zhujiang Formation contains no abnormal pressure.Instead, the interval is predominantly 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 temperature-pressure 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.