鄂尔多斯盆地郑庄油区长6储层成岩作用及其对储层的影响

Diagenesis of Chang 6 reservoir in Zhengzhuang area,Ordos Basin and its effect on reservoir quality

鄂尔多斯盆地郑庄油区长6油层为三角洲前缘水下分流河道砂体,以长石砂岩为主,具有粒度细、成分成熟度低、结构成熟度较高的岩石学特征,是典型的低孔低渗储集层.其成岩作用类型主要有压实作用、压溶作用、胶结作用、交代作用、溶蚀作用及破裂作用.对成岩演化序列的研究表明,长6储层砂岩的成岩阶段主要处于中成岩A期—中成岩B期.在成岩过程中,强烈的压实作用及胶结作用导致原生孔隙丧失殆尽,是形成特低渗透储层的主要原因;而晚期的溶蚀作用,特别是浊沸石的溶解,使得储层的孔隙度和渗透率有所改善,这才使得鄂尔多斯盆地长6层发育部分"甜点"储层,成为有利的储集相带.

The deposition of Chang 6 reservoir is controlled by delta front subaqueous distributary channel.The reservoir mainly consists of fine feldspathic sandstone.The reservoir rock is characterized by fine grain size,low compositional maturity and high texture maturity,so it is typical low-porosity and low-permeability reservoir.Its diageneses mainly include compaction,pressure solution,cementation,metasomatism,dissolution and fracturing.The study on the diagenetic evolution of Chang 6 sandstone shows that its diagenesis stage mainly is in A to B stage of middle diagenesis.Mechanical compaction and cementation result in the almost complete loss of primary pore,this is why the reservoir is of superlow permeability in the early diagenetic phase;but in the late diagenetic phase,the dissolution,especially the dissolution of laumontite,improves the porosity and permeability of the reservoir,which makes some ' sweat reservoirs' develop in the Chang 6 reservoir and they become favorable reservoir facies belts in Ordos Basin.