深部埋藏条件下砂岩中碳酸盐胶结物的成因及储层改造——以济阳坳陷始新统孔店组为例

Origin of Carbonate Cements and the Transformation of the Reservoir in Sandstone under the Deep Burial Condition——A Case Study on Eocene Kongdian Formation in Jiyang Depression,Bohai Bay Basin

济阳坳陷始新统孔店组深部碎屑岩中普遍发育碳酸盐胶结物。依据普通薄片、扫描电镜、X衍射、阴极发光、流体包裹体测温和碳氧同位素等实验结果,对济阳坳陷始新统孔店组深部砂岩中的碳酸盐胶结物进行了深入研究。结果表明:碳酸盐胶结物类型有方解石、铁方解石、铁白云石和菱铁矿等,胶结方式有早期基底式胶结、成岩期点状胶结、成岩后期裂缝充填,胶结物的纵向上和横向上分布具有一定的规律性;早期基底式胶结主要形成于原始沉积水介质的化学沉积分异作用,这种沉积分异作用主要发生在湖盆沉积的同生期,由于化学物质的饱和度分异造成;成岩期胶结物主要跟成岩演化过程中流体的自由流动、粘土矿物转化、有机质的演化和地质环境的变化有关,断裂构造活动形成的深部热液也是形成部分碳酸盐胶结物的主要原因;碳酸盐胶结物对储层具有明显的改造作用,早期基底式胶结沉淀作用对岩石储层具有强烈胶结作用和抗压实作用,成岩期碳酸盐的沉淀作用对储层空间具有明显的堵塞作用,成岩过程中的碳酸盐矿物的溶解作用提高了深部地层的储层质量。

Carbonate cements commonly developed in the deep clastic rocks of the Eocene Kongdian Formation in the Jiyang Depression,Bohai Bay Basin.On the basis of general thin-sections,scanning electron microscope,X-ray diffraction,cathodoluminescence,measurement of fluid inclusions and carbon oxygen isotope results,in this paper,carbonate cements of deep sandstone of the Eocene Kongdian Formation in the Jiyang Depression have been deeply researched.The results showed that：the type of carbonate cements are calcite,iron calcite,ankerite and siderite etc,cementation including early basal cement,diagenetic punctate cementation,fracture filling developing in late stage of diagenesis,cement in vertical and horizontal distribution has certain regularity.Early basal cement formed mainly in chemical sedimentary differentiation in the original water medium,mainly occurred in the contemporaneous lacustrine deposition,caused by the chemical saturation differentiation.Diagenetic carbonate cements is relate to the free flow of fluid,transformation of clay minerals,thermal evolution of organic matter,geological environment change,deep thermal fluid caused by the fault activitiy may also the reason.Carbonate cements has obvious effect on reservoir reconstruction,early basal cement have stong cementation and anti compaction,diagenetic carbonate sedimentation significantly blocked reservoir space,dissolution of carbonate cements during the diagenetic process improved the quality of deep reservoir.