强超压储集层中黏土矿物及其对储集物性的影响

根据薄片、扫描电镜、X衍射、地层测试等资料,对比了渤中坳陷A2-1构造东营组常压和强超压油层中黏土矿物特征差异,分析了黏土矿物对储集层品质的影响。研究结果表明,与正常压力储集层相比,强超压储集层伊利石含量高,高岭石含量低,强超压封闭环境溶出物不能迁出系统造成K＋、Na＋等碱性离子富集,不利于高岭石大量形成,有利于伊利石生成。强超压储集层伊蒙混层中蒙脱石含量普遍高于同深度的泥岩和正常压力储集层,显示了超压对黏土矿物转化的抑制作用。强超压层高岭石含量与渗透率正相关,伊利石含量与渗透率负相关,强超压封闭体系溶出物的富集促进了伊利石的发育,对储集层渗透率影响较大。整体粒度较粗的厚层超压层,中等强度的超压层,强超压储集层内粒度相对较粗、厚度大的夹层具备高产潜力。

Clay Minerals and Their Influences on Petrophysical Property in the Strong Overpressured Reservoir

By using the data of thin section,SEM,X-ray diffraction and formation testing,the differences of clay mineral between normal pressured reservoir and strong overpressured reservoir of Dongying formation in A2-1 structure in Bozhong depression were compared,and the influence of clay mineral on reservoir quality was analyzed.The results show that the strong overpressured reservoir is characterized by low kaolinite content and high illite content compared with the normal pressured reservoir,for the reason that the strong overpressured enclosed system is hard to allow the dissolved resultants to move out,leading to enrichment of alkaline ions such as K+ and Na+,favorable for illite generation rather than kaolinite.The montmorillonites content of illite/montmorillonite mixing layer is normally higher than that of mudstone and normal pressured reservoir,which indicates the inhibition of over-pressure to clay mineral evolution in strong overpressured reservoir,with positive correlation for kaolinite content and negative correlation for Illite content to permeability.So the development of illite in this system has a big impact on permeability of reservoir.It is concluded that thick and relatively coarse particle interlayers in coarse and thick overpressured reservoir,moderate overpressured reservoir and strong overpressured reservoir could be of high-yield potentials.