摘要
古老海相碳酸盐岩铀和铅含量普遍较低、且成岩组构直径小，很难取得足够的粉末样品，常规的溶液法铀铅同位素定年在古老海相碳酸盐岩中难以推广应用。针对以上问题，中国石油集团碳酸盐岩储层重点实验室和昆士兰大学（UQ）地球科学院放射性同位素实验室两家共同开发激光原位U-Pb同位素定年技术，并应用于塔里木盆地寒武系肖尔布拉克组储层成岩-孔隙演化研究。通过充填孔洞、孔隙和裂缝中不同期次白云石和方解石胶结物的测年，指出寒武系肖尔布拉克组白云岩储层的埋藏成岩过程是孔隙和孔洞逐渐被充填的过程。孔洞的充填作用主要发生在早加里东期，孔隙的充填作用主要发生在中加里东期和印支期，加里东和印支期断裂作为热液运移的通道，为充填孔洞和孔隙的胶结物提供了物源，未被白云石、方解石和硅质胶结物充填的残留孔洞、孔隙和裂缝构成了主要储集空间，建立了肖尔布拉克组白云岩储层的成岩-孔隙演化史。这些认识与该地区的构造-埋藏史、盆地热史具有很高的吻合度，结合下古生界烃源生烃史，为古老海相胶结物形成时间确定、成岩-孔隙演化研究和油气运移前有效孔隙评价提供了利器。
Abstract
The Laser Ablation (LA)Multi-Collector Inductively Coupled Plasma Mass Spectrometry (MC-ICP-MS) technique, co-developed by the CNPC Key Laboratory of Carbonate Reservoir and School of Earth and Environmental Sciences, The University of Queensland, has huge potential to overcome the difficulty in sampling and dating ultra-low concentration U-Pb minerals in ancient marine carbonates that are relatively smaller in diameter in diagenetic fabric, which was untenable by the conventional isotope dilution (ID) methods. The in-situ analysis by LA combined with MC-ICP-MS has been applied to the study on the diagenesis and porosity evolution of the Cambrian Xiaoerbulake reservoir, Tarim Basin.By dating of dolomitic and calcitic cements from filled vugs, matrix pores and fractures in different stages, we suggested that the burial diagenetic history of dolomite reservoir in the Cambrian Xiaoerblake Formation mainly features the filling of primary pores and vugs generated under karstification. The filling of vugs mainly occurred during the early Caledonian, while the filling of matrix pores mainly occurred in the middle Caledonian and Indosinian. Fractures activated during the Caledonian and Indosinian served as the channels for hydrothermal migration, providing the materials to cement the vugs and pores; while the residual vugs, pores and fractures with no filling of dolomite, calcite and siliceous cements were the main reservoir space. The diagenesis and porosity evolution history of dolomite reservoir in the Cambrian Xiaoerbulake Formation, Tarim Basin, was hence established. The understandings mentioned above are highly consistent with the tectonic-burial history and basin thermal history in the study area, which may be effective tools to date the ancient marine carbonate reservoir cements, to reconstruct diagenesis and porosity evolution history, and to evaluate effective pores before hydrocarbon migration in the ancient marine carbonates.
论文详情