摘要
四川盆地西部(以下简称川西地区)中二叠统栖霞组白云岩勘探开发实践证实为重要储集岩,但关于其成因尚存争议。为了进一步弄清该区栖霞组白云岩成因,为寻找优质白云岩储层提供依据,以川西地区栖霞组典型野外剖面和钻井岩心样品为研究对象,通过岩石学、稀土配分模式以及Y/Ho比值分析探究了白云岩化流体与海水和峨眉山玄武岩的关系。研究结果表明:①栖霞组白云岩主要有晶粒白云岩、残余颗粒白云岩、鞍状白云石和脉体白云石4类;②晶粒白云岩和残余颗粒白云岩稀土配分模式、Y/Ho比值具海源流体特征,δEu值偏高,可能受峨眉山玄武岩喷发高温效应的影响;③鞍状白云石和脉体白云石成因与峨眉山喷发带距离有关,近带鞍状白云石及脉体白云石的稀土配分模式、Y/Ho比值与峨眉山玄武岩相近,δEu大于1,推测为与峨眉山玄武岩喷发事件有关的热液成因,远带鞍状白云石和脉体白云石稀土配分模式、Y/Ho比值具海源流体特征,指示为浅埋藏期海水经高温流体加热后沿孔隙充填而成。结论认为,川西地区栖霞组白云岩主要为浅埋藏成因但受热事件改造,四川盆地西北缘台地边缘相与峨眉火山岩省外带叠加区为有利储集相带,西南缘发育的热液白云石不利于油气储集。
Practical exploration and development prove that Middle Permian Qixia Formation dolomites in the western Sichuan Basin are important reservoir rocks,but their genesis is still controversial.In order to clarify the genesis of Qixia Formation dolomites in this area and provide a basis for searching for high-quality dolomite reservoirs,this paper takes the typical field profiles and drilling core samples of Qixia Formation in the western Sichuan Basin as the research objects to discuss the relationships between dolomitic fluid and seawater and Emeishan basalt by analyzing petrology,rare earth element pattern and Y/Ho ratio.And the following research results are obtained.First,Qixia Formation dolomites can be classified into four types,including crystalline grain dolomites,residual grain dolomites,saddle dolomites and vein dolomites.Second,the rare earth element pattern and Y/Ho ratio of crystalline grain dolomites and residual grain dolomites have the characteristics of marine fluid,and the δEu value is higher,which might be the result of the high temperature effect induced by the eruption of Emeishan basalt.Third,the genesis of saddle dolomites and vein dolomites is related to the distance from the Emeishan eruption zone.The rare earth element pattern and Y/Ho ratio of saddle dolomites and vein dolomites near the Emeishan eruption zone are close to those of Emeishan basalt,and theδEu is higher than 1,which suggests that the dolomites are of hydrothermal genesis related to the eruption event of Emeishan basalt.The rare earth element pattern and Y/Ho ratio of saddle dolomites and vein dolomites far from the Emeishan eruption zone have the characteristics of marine fluid,which indicates that the dolomites are formed by the filling of seawater along pores after being heated by high-temperature fluid in the period of shallow burial.In conclusion,Qixia Formation dolomites in the western Sichuan Basin are mainly of shallow burial genesis,but due to the reworking of thermal events,the superimposition zone of the marginal platform along the northwestern margin of the Sichuan Basin and the outer zone of Emeishan igneous province is the favorable reservoir facies belt,and the hydrothermal dolomites developed along the southwestern margin are not favorable for hydrocarbon accumulation.
作者
马慧
苏中堂
梁茹
方继瑶
林良彪
MA Hui;SU Zhongtang;LIANG Ru;FANG Jiyao;LIN Liangbiao(Institute of Sedimentary Geology,Chengdu University of Technology,Chengdu,Sichuan 610059,China;State Key Laboratory of Oil&Gas Reservoir Geology and Exploitation//Chengdu University of Technology,Chengdu,Sichuan 610059,China;Institute of Petroleum Exploration and Development,Sinopec Zhongyuan Oilfield Company,Puyang,Henan 457001,China;Technical Innovation Center for Shale Gas Exploration and Development in Complex Structural Areas,Ministry of Natural Resources,Chengdu,Sichuan 610091,China)
出处
《天然气工业》
EI
CAS
CSCD
北大核心
2021年第12期49-59,共11页
Natural Gas Industry
基金
国家自然科学基金项目“热液活动对川东中二叠统茅口组的影响及与峨眉山大成岩省的关系”(编号:41872115)。
