Feng Tao, Feng Yong, Tang Jiguang, Cui Yue, Wang Bin, Peng Fuxing, Qin Dechao, Zhang Yue
School of Geosciences, Yangtze University, Wuhan 430100, China.
Key Laboratory of Exploration Technologies for Oil and Gas Resources, Ministry of Education, Yangtze University, Wuhan 430100, China.
ACS Omega. 2022 Aug 11;7(33):29420-29432. doi: 10.1021/acsomega.2c03737. eCollection 2022 Aug 23.
The main types of diagenesis, diagenetic minerals and their formation time sequence in the Ordovician ultradeep (>7000 m total depth) carbonate reservoir represented by the Yingshan and Penglaiba Formations (well Tashen-6, Tahe Oilfied, Tarim Basin), are determined by applying microscopic observations, microscopic fluorescence detection, and cathodic luminescence analysis in petrographic thin sections. The distinct periods of reservoir diagenesis and hydrocarbon-related events are determined by analyzing the development characteristics of hydrocarbon inclusions and their relationship with the host minerals. The charging periods of hydrocarbon inclusions are identified by constraining the homogenization temperatures of inclusions. The obtained results indicate that the Ordovician Yingshan and Penglaiba formations have experienced at least three periods of hydrocarbon charging and one period of structural transformation. Their relative time sequence relationship with diagenesis processes is as follows: The limestone dissolution of the Yingshan Formation developed initially, and the first period of hydrocarbon charging occurred (during the late Caledonian). The second period of hydrocarbon charging occurred due to the continuous modification influence of dissolution (late Hercynian-early Yanshanian). The limestones of the Penglaiba Formation were exposed to strong tectonism during the second period of hydrocarbon charging in the Yingshan Formation; thus, intralayer microfractures were formed. Additionally, the first period of hydrocarbon charging in the Penglaiba Formation occurred together with the dolomite reservoir (late Hercynian-early Yanshanian). During the subsequent period, dissolution occurred again due to the continuous increase in burial depth. The third period of hydrocarbon charging developed concurrently with the early fractures (late Himalayan). Finally, the unceasing deepening of the strata accompanied by tectonic activity led to the early intergranular dissolution pores to be cut by late microfractures, which caused the crude oil to convert into bitumen through secondary modifications.
以塔里木盆地塔河油田塔深6井鹰山组和蓬莱坝组为代表的奥陶系超深层（总深度>7000米）碳酸盐岩储层，通过对岩石薄片进行显微镜观察、显微荧光检测和阴极发光分析，确定了主要的成岩作用类型、成岩矿物及其形成时间顺序。通过分析烃类包裹体的发育特征及其与寄主矿物的关系，确定了储层成岩作用和与烃类相关事件的不同时期。通过限制包裹体的均一温度来确定烃类包裹体的充注时期。研究结果表明，奥陶系鹰山组和蓬莱坝组至少经历了三期烃类充注和一期构造改造。它们与成岩作用过程的相对时间顺序关系如下：鹰山组石灰岩溶解作用首先发育，发生了第一期烃类充注（加里东晚期）。由于溶解作用的持续改造影响，发生了第二期烃类充注（海西晚期—燕山早期）。在鹰山组第二期烃类充注期间，蓬莱坝组石灰岩遭受强烈构造作用，形成层内微裂缝。此外，蓬莱坝组第一期烃类充注与白云岩储层同期发生（海西晚期—燕山早期）。在随后的时期，由于埋藏深度不断增加，再次发生溶解作用。第三期烃类充注与早期裂缝同期发育（喜马拉雅晚期）。最后，地层不断加深并伴随构造活动，导致早期粒间溶解孔隙被晚期微裂缝切割，原油通过二次改造转化为沥青。
