塔里木盆地顺北地区克拉通内走滑断裂带中-下奥陶统储集体方解石脉形成及其与油气充注耦合关系

Coupling relationship between formation of calcite veins and hydrocarbon charging in Middle-Lower Ordovician reservoirs in strike-slip fault zones within craton in Shunbei area， Tarim Basin

刘建章 蔡忠贤 滕长宇 张恒 陈诚

Jianzhang LIU Zhongxian CAI Changyu TENG Heng ZHANG Chen CHEN

塔里木盆地顺北油气田为克拉通内走滑断裂多期活动控制下形成的碳酸盐岩超深层油气田，不同断裂带及同一走滑断裂带不同分段的油气性质和油气丰度等均存在显著差异。基于岩心和岩石薄片观察以及阴极发光、微区原位微量元素-稀土元素、流体包裹体的系统分析，对塔里木盆地顺北1号和顺北5号走滑断裂带中-下奥陶统储集体中的裂缝脉体序次、成脉流体来源及其与油气充注耦合关系进行研究，并结合走滑断裂演化过程和油气分布特征，探讨了顺北地区油气差异聚集的控制因素。结果表明：顺北1号和顺北5号走滑断裂带中-下奥陶统至少发育4期方解石脉体（Cal-1，Cal-2，Cal-3，Cal-4）。Cal-1成脉流体主要为海源性流体，Cal-2，Cal-3和Cal-4成脉流体来源于同地层成岩流体。Cal-2，Cal-3和Cal-4脉体的形成分别与加里东晚期—海西早期、海西晚期—印支期、燕山期—喜马拉雅期构造活动和油气充注相伴生。不同断裂带油气充注过程存在差异，顺北5号断裂带主充注期为海西晚期—印支期，顺北1号断裂带主充注期为海西晚期—印支期及燕山期—喜马拉雅期。走滑断裂构造样式及演化历史控制下的油气差异充注过程是顺北地区油气差异聚集的关键。

Shunbei oil/gas field is of the ultra-deep carbonate type controlled by multi-stage strike-slip faulting within the craton. The significant differences on the oil/gas property and abundance are shown in different fault zones even different segments in a fault zone. An integration of the core and thin section observation， cathodoluminescence， in-situ trace and rare earth element （REE） analysis， systematic analysis of fluid inclusions， is applied to study the sequence of fracture vein formation， sources of vein-forming fluids and their coupling relationships with hydrocarbon charging in the Middle-Lower Ordovician reservoir of the No.1 and 5 strike-slip fault zones in Shunbei area. We also investigate the factors controlling differential hydrocarbon accumulation in Shunbei area while understanding the evolution of strike-slip faults and the hydrocarbon accumulation pattern. The results show that there are at least four phases of calcite vein development， that is， Cal-1， Cal-2， Cal-3， and Cal-4， respectively， in the Middle-Lower Ordovician reservoir of the No. 1 and 5 strike-slip fault zones in Shunbei area. The vein-forming fluids of Cal-1 are mainly sea-sourced fluids， while that of Cal-2， Cal-3 and Cal-4 are derived from diagenetic fluids in the reservoir where the veins occur. The formation of Cal-2， Cal-3 and Cal-4 calcite veins is associated with tectonic activities and hydrocarbon charging in the Late Caledonian to Early Hercynian， the Late Hercynian to Indosinian， and the Yanshan-Himalayan， respectively. The strike-slip fault zones are different in hydrocarbon charging， as shown by that the main charging phase of the No. 5 fault zone was during the Late Hercynian to Indosinian， while the main charging period of No. 1 fault zone was during the Late Hercynian to Indosinian， and Yanshan-Himalayan. The differential hydrocarbon charging controlled by strike-slip fault structural style and evolution history is the key to differential hydrocarbon accumulation in Shunbei area.

10.11743/ogg20230110