白云石胶结物特征及其对深层白云岩孔隙的作用  

Characteristics of Dolomite Cement and Its Effect on the Porosity of Deep Dolomite

作　　者：屈海洲[1] 陈润 徐伟[2] 张云峰[1] 张亚[2] 何溥为 唐松[3] 李文皓 Qu Haizhou;Chen Run;Xu Wei;Zhang Yunfeng;Zhang Ya;He Puwei;Tang Song;Li Wenhao(School of Geosciences&Technology,Southwest Petroleum University,Chengdu 610500,China;Exploration and Development Research Institute,PetroChina Southwest Oil and Gas Field Company,Chengdu 610051,China;Chuanzhong Oil and Gas Mine,PetroChina Southwest Oil and Gas Field Company,Suining 629000,Sichuan,China;Exploration Division,PetroChina Southwest Oil and Gas Field Company,Chengdu 610051,China)

机构地区：[1]西南石油大学地球科学与技术学院,成都610500 [2]中国石油西南油气田分公司勘探开发研究院,成都610051 [3]中国石油西南油气田分公司川中油气矿,四川遂宁629000 [4]中国石油西南油气田分公司勘探事业部,成都610051

出　　处：《吉林大学学报(地球科学版)》2025年第2期401-416,共16页Journal of Jilin University:Earth Science Edition

基　　金：国家自然科学基金项目(41702163);中国石油-西南石油大学创新联合体科技合作项目(2020CX010301)。

摘　　要：深层白云岩是近年深部勘探的重点,其孔隙内多见白云石胶结,但白云石胶结物晶粒赋存组合方式及其对孔隙的作用研究较少。因此,以四川盆地高磨地区下寒武统龙王庙组为例,综合岩心、薄片、阴极发光、碳氧同位素及包裹体等资料,研究其白云石胶结物类型、特征、结构、体积分数及其对孔隙的影响。白云石胶结物晶体在形态上主要有半菱形、菱形、环带状和鞍状等,粒径包含粉晶—巨晶。胶结物晶体与孔洞形成内衬状、桥接状和镶嵌状三种结构。使用发育频率(发育某种结构的样品数/颗粒白云岩或晶粒白云岩样品总数)来表征某种结构的发育程度,白云岩中镶嵌状结构最发育(发育频率为48.3%~89.5%),桥接状次之(22.4%~73.7%),内衬状最弱(8.6%~55.2%)。内衬状结构和桥接状结构主要发育在颗粒白云岩中,体积分数分别为0~15%和25%~50%,且其发育程度随细—粉晶白云石胶结物体积分数增加而增强;镶嵌状结构在白云岩中普遍发育,体积分数主要为50%~100%,且其发育与中晶巨晶白云石体积分数正相关。内衬状结构和桥接状结构主要形成于同生成岩阶段中成岩阶段,镶嵌状结构主要形成于晚成岩阶段。内衬状结构及桥接状结构形成较早可降低成岩进程中压溶压实对孔隙的破坏,而镶嵌状结构破坏残余孔隙。以主要发育镶嵌状结构层段的孔隙度为基准,主要发育内衬状结构和桥接状结构层段的孔隙度可提高约50%。Deep dolomite has been a key focus of deep exploration in recent years,with dolomite cementation commonly found in its internal pores.However,there is relatively less research on the combination of dolomite cement grain occurrence and its effect on pores.Therefore,taking the Longwangmiao Formation of the Lower Cambrian in the Gaomo area of the Sichuan basin as an example,comprehensive data such as core samples,thin sections,cathodoluminescence,carbon-oxygen isotopes,and inclusions were used to study the types,characteristics,structures,volume fraction,and their effects on pores of dolomite cement.The crystals of dolomite cement mainly have shapes such as semi rhombus,rhombus,ring shaped,saddle shaped,etc.,with particle sizes ranging from powder crystals to giant crystals.Cement crystals and pores form three types of structures:lining,bridging,and embedding.Using the frequency of development(the number of samples that develop a certain structure/the total number of samples of granular dolomite or grain dolomite)to characterize the degree of development of a certain structure,the embedding structure is the most developed in dolomite(48.3%-89.5%),followed by the bridging structure(22.4%-73.7%),and the lining structure is the weakest(8.6%-55.2%).The inner lining structure and bridging structure are mainly developed in granular dolomite,with volume fraction of 0 to 15%and 25%to 50%,respectively,and their development degree increases with the volume fraction of fine-grained dolomite cement.Embedding structures are commonly developed in dolomite,with a volume fraction mainly ranging from 50%to 100%,and their development is positively correlated with the volume fraction of medium crystalline to giant crystalline dolomite.The inner lining structure and bridging structure are mainly formed during the syndiagenetic stage to the middle diagenetic stage,while the embedding structure is mainly formed during the late diagenetic stage.The formation of inner lining and bridging structures earlier can reduce the damage to pores ca

关 键 词：四川盆地 深层白云岩 白云石胶结物 孔隙 龙王庙组 

分 类 号：P618.13[天文地球—矿床学]