作　　者： ; ; ;

机构地区： 吉林大学地球科学学院

出　　处： 《地球科学》 2019年第8期2751-2760,共10页

摘　　要： 渤海海域渤中凹陷北陡坡带沙一段发育湖相碳酸盐岩及相关的混积岩类油藏,探明储量超亿方,产量高,埋深超过3 200~3 800 m.分析表明:湖相碳酸盐岩段及混积岩段发生了强烈的白云岩化作用,溶蚀作用强,储层物性好,孔隙度可超过25%.早期研究认为生屑的溶蚀是储层物性改善的重要因素.进一步研究表明,除了上述因素外,储层还受到了深部热流体的影响.通过包裹体激光拉曼分析证实,储层中存在大量含CO2、N2、H2S、H2的包裹体,CO2最高含量超过70%;研究区多个构造富含CO2,碳同位素及氦同位素显示其为幔源成因;对储层中大量的自生黄铁矿分析表明,大部分黄铁矿Co/Ni比值大于1,显示了热液成因;在缝洞及大孔隙内沉淀典型微晶鞍形白云石,具弧形晶面,波状消光,扫描电镜下鞍形白云石内见密集的生长纹.综合分析表明,富CO2深部幔源热液侵位时间为3 Ma以来,侵位后造成了白云石晶间残余方解石的大量选择性溶解;酸性流体对粒内长石也产生了强烈的溶蚀作用,形成了大量砾石及岩屑的铸模孔并沉淀高岭石,流体上述溶解作用对储层段物性改善起到了决定性影响.随着方解石及长石的溶解,流体PH值的升高,盐度的增加,储层出现明显的白云岩化作用,晚期白云石的较高的均一温度及鞍形白云石证实了深部热液对白云岩化的贡献.幔源流体主要来自深大断裂及早期火山后期的排气、排液作用. Several high-yielding lacustrine carbonate rock and mix-deposit reservoirs with the total proven reserves of more than1×108 cubic metres have been found in the actic area of the north part of Bozhong depressoin,with the reservoir depth of 3 200~3 800 meters.The research shows that there are strong dolomitization and dissolution in the lacustrine carbonate rock and mixdeposit rock,and the porosity can be over 25%.Early research suggests that the dissolution of biodetritus is the decisive factor to improve reservoir physical property.But the further research shows obvious deep thermal fluid activity evidences in this belt,and deep thermal fluid plays a decisive role on forming the high quality reservoirs.Based on the Laser Raman analysis,there are a large number of inclusions which contain CO2,N2,H2 S and H2,and the high content of CO2 can be over 70%;There are 3 CO2-bearing structures found at the Actic Area of Shijiutuo Uplift,theδ13 C CO2 values,R/Ra values values show that CO2 was derived from the mantle.There are a lot of pyrite in the lacustrine carbonate rock,and the Co/Ni ratio of most pyrite is greater than 1,which indicates most of the pyrite derived from the thermal fluid.Saddle dolomite are found at the fractures and big pores,which have the typical arc-shaped crystal and wavy extinction characteristics,and the crystal size is about 0.05~0.10 mm.Dense growth striations are observed under the SEM.According to the thermal history and inclusion homogenization temperature drop points,the thermal fluid activity time is 3~0 Ma.The CO2 thermal fluid activities produced strong dissolution of calcite cements and feldspars in reservoir,which played an important role on the increasing porosity.With the dissolution of the calcite cements and the volcano lithic fragments and gravels,the PH value and salinity of fluid increased,which resulted in strong dolomitization.The higher inclusion homogenization temperature of late stage dolomite and the saddle-like dolomite show that the thermal fluid promote the dolomitiza

关 键 词： 渤海湾盆地 渤中凹陷 幔源流体 湖相碳酸盐岩 白云岩化 鞍形白云石 石油地质

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