查干凹陷早白垩世热流体活动的证据及其对巴音戈壁组碎屑岩储层的影响

基于沉积、储层和构造特征，应用流体包裹体和碳、氧同位素等技术手段，结合岩心、薄片及扫描电镜观察，发现查干凹陷早白垩世苏红图组沉积时期为走滑-拉分断陷期，伴随多期中-基性安山岩和玄武岩为主的火山活动及其对应的热流体活动。苏红图期火山喷发及热流体活动，影响了巴音戈壁组埋深2 800 m以下地层，主要体现在古大地热流异常高值、包裹体均一温度异常增高、碳同位素显示无机成因特征、镜质体反射率突变及粘土矿物转化异常这5个方面。深部的热流体携带CO₂等气体，主要沿毛西断裂上侵，进入乌力吉构造带，通过微裂缝和不整合面等通道发生横向运移，主要溶蚀巴音戈壁组储层碳酸盐等矿物，其次为长石颗粒。溶蚀作用发育的优先部位，主要在靠近控制岩浆侵入体的深大断裂，其次受不整合面及次级断裂和裂缝等控制；向凹陷内部，溶蚀作用减弱。深部热流体活动对区内有机质热演化和储层物性的影响，是研究区内溶蚀孔洞发育及分布的主控因素，也是勘探大规模油气藏的关键。

The Early Cretaceous thermal fluid activities and their impacts on clastic reservoir rocks in the Bayingebi Formation of Chagan Sag

Analyses of sedimentary,reservoir,and structural characteristics,were combined with application of such technologies as fluid inclusion and carbon and oxygen isotopes techniques,and observations of cores,thin sections and scanning electron microscope images,to study deposition during the Early Cretaceous Suhongtu stage in Chagan Sag.The result indicates a strike-slip and pull-apart faulting stage accompanied by multi-stage volcanic activities of thermal fluid flows dominated by neutral-basic andesite and subordinate basalt.The thermal fluid activities during the Suhongtu volcanic eruptions exerted significant influence upon layers deeper than 2 800 meters in the Bayingebi Formation and resulted in an abnormal high value of paleo-heat flow,an abnormal increase of homogenization temperature of inclusions,inorganic characteristics of carbon isotopes,an abrupt change in vitrinite reflectance,and an abnormal conversion of clay minerals.The thermal fluids from the deep layers carried gases (mainly CO₂) and migrated upward along the Maoxi faults into the Wuliji tectonic belt.They then migrated horizontally along micro fissures and channels formed by unconformities to dissolve mostly carbonates and feldspar in the Bayingebi Formation.The signs of erosion were mainly found in places near deep-rooted large faults that controlled the migration of the fluids.Unconformities as well as secondary faults and fractures also played a part in controlling the flow of the thermal fluids.The dissolution was observed to be weakened toward the inner part of the sag.We therefore suggest that a study on the effect of deep thermal fluids activities upon the thermal evolution of organic matters and physical properties of reservoirs is the key to understand the distribution of dissolved pores and cavities in the study area and to explore for high-quality reservoirs there.