渤中坳陷石臼陀凸起东段幔源CO2充注对储集层粘土矿物的影响

探讨了渤中坳陷石臼陀凸起东段CO2来源及CO2充注对储层粘土矿物的影响.研究表明,CO2中δ13C组成较重,R/Ra值较大,CO2为幔源成因；控盆的深大断裂是CO2的主要运移通道；CO2热流体晚期充注对砂岩储集层粘土矿物产生了明显的影响:CO2热流体侵位后形成的热波动效应加快了储集层中伊蒙混层粘土的演化,含CO2储集层中伊蒙混层中蒙脱石含量要比同深度的泥岩低15％ ～30％;CO2热流体晚期侵入加剧了长石的溶蚀作用,长石溶蚀促进了自生高岭石的大量形成；CO2热流体侵位后形成的偏酸性环境抑制伊利石生长,促进了其他粘土矿物向高岭石转化；含CO2储集层以少见的高自生高岭石、低伊利石为特征,这对储层物性改善起到了决定性的影响.

The impact of mantle source CO2 on clay minerals of clastic reservoirs in the east part of Shijiutuo symon fault, Bozhong depression

The origin of CO2 and the alteration of CO2 into clay minerals in eastern Shijiutuo symon fault of Bozhong depression were studied in this paper.The elevated δ13C and R/Ra values show the mantle-derivation of CO2.The basin-controlling deep fault was the main migration pathway of CO2 fluid.CO2 fluid injection had obvious impact on clay minerals.CO2 late injection caused obvious thermal fluctuation and brought out the result that the montmorillonite of the illite/montmorillonite mixing layer was 15%～30% lower than that of mudstone at the nearby depth.Because of late accumulation of CO2,acidic environment of reservoir bed lasted for a long time,which promoted dissolution of feldspar and formation of kaolinite.Acidic environment inhibited illite in favor of the transform of other clay minerals into kaolinite.The CO2-bearing reservoir bed was characterized by high authigenic kaolinites and low illite,which played a decisive role in reservoir quality improvement.