川东寒武系龙王庙组白云岩地球化学特征、成因及油气意义  

Geochemical characteristics,genesis and hydrocarbon significance of dolomite in the Cambrian Longwangmiao Formation,eastern Sichuan Basin

作　　者：任影[1,2] 钟大康[1,2] 高崇龙 杨雪琪[1,2] 谢瑞[1,2] 李卓沛 邓闵心[4] 周勇成[5] 

机构地区：[1]中国石油大学地球科学学院,北京102249 [2]中国石油大学油气资源与探测国家重点实验室,北京102249 [3]中国石油西南油气田公司勘探开发研究院,四川成都610041 [4]重庆工业职业技术学院,重庆401120 [5]重庆商务职业学院,重庆401331

出　　处：《石油学报》2016年第9期1102-1115,共14页Acta Petrolei Sinica

基　　金：国家重点基础研究发展计划(973)项目(2011CB201104);国家自然科学基金项目(No.41472094)资助

摘　　要：在岩石学、矿物学特征研究基础上,通过分析主、微量元素及碳、氧同位素特征,系统研究四川盆地东部寒武系龙王庙组白云岩地球化学特征及成因,并对其油气地质意义进行探讨。结果表明：龙王庙组白云岩多位于地层的中上部,晶粒白云岩广泛发育,颗粒白云岩发育程度低;白云岩的白云石百分含量在48.6%-75%;Mg/Ca值总体较低,并划分为MgO与CaO呈正相关性和负相关性2种类型;白云岩总体具有高Fe、Na和低Sr、Mn含量特征,仅部分白云岩Mn含量相对较高;相较于同期海水值,多数白云岩的δ13 C值偏正,δ18 O值偏负。结合区域地质背景及上述地球化学特征,研究认为四川盆地东部龙王庙组白云岩主要为渗透回流白云石化成因,蒸发浓缩白云石化、埋藏白云石化发育程度较低,整体上龙王庙组白云石化作用并不彻底;进一步总结川东地区龙王庙组白云石化模式,并结合沉积相带展布、白云石化对储集层控制作用等方面对有利储集层进行预测,指出川东地区龙王庙组白云岩有利储集层主要发育在齐岳山断裂带周缘。Based on the researches on petrographic and mineralogical characteristics and the analyses of major elements,trace elements,carbon and oxygen isotopic characteristics,this paper systematically explores the geochemical characteristics,genesis and hydrocarbon geologic significance of dolomite in Cambrian Longwangmiao Formation,Eastern Sichuan Basin.The sample analysis shows that the dolomite in Longwangmiao Formation is mostly located at the mid-upper part of formation with wide development of crystal dolomite and low-level development of grain dolomite.The content of dolomite ranges from48.6%to75%;the Ca/Mg ratio is generally small,and divided into two types according to the positive correlation and negative correlation between MgO and CaO.Overall,the dolomite has high Fe and Na contents,low Sr and Mn contents;only apart of dolomite has high Mn content.Compared with the seawater values in the same period,most dolomite has partially positiveδ13C value and partially negativeδ18 O value.In combination with regional geological settings and above geochemical characteristics,the research indicates that the dolomite in Longwangmiao Formation,Eastern Sichuan Basin is mainly developed by seepage reflux dolomitization,and is featured by the low degree of by evaporation-concentrating dolomitization and burial dolomitization,revealing an inadequate dolomitization in Longwangmiao Formation.The dolomitization patterns in Longwangmiao Formation,Eastern Sichuan Basin are further summarized.On this basis,the favorable reservoirs can be predicted in combination with the control effect of sedimentary facies belt distribution and dolomitizaton on reservoirs.It is pointed out that the favorable reservoirs of dolomite in Longwangmiao Formation,Eastern Sichuan Basin are mainly developed in the periphery of Qiyue Mountain fault zone.

关 键 词：四川盆地东部 寒武系 龙王庙组 白云岩成因 地球化学特征 

分 类 号：TE122.113[石油与天然气工程—油气勘探]