柴达木盆地西南区古近系及新近系砂岩储层

根据40余口钻井的岩石学资料，较系统地描述了柴达木盆地西南区古近系及新近系的砂岩储层特征：（1）砂岩储层的岩石（矿）成分在时空上呈现规律性的变化。在研究区东南和西北两侧，砂岩成分成熟度和结构成熟度均比中部地区明显偏低；从古近系到新近系，砂岩的成分成熟度和结构成熟度均逐渐降低，这与区域上由早到晚构造活动逐渐增强是一致的。砂岩储层岩石学的这种变化明显地影响到其储集性质，本区东南和西北两侧砂岩储层性质比中部地区变差即与此有关。（2）砂岩储层的孔隙类型以原生孔隙为主。前人大都认为本区砂岩储层的孔隙类型以次生孔隙为主，尤其是下干柴沟组，主要发育次生孔隙。本文认为古近系及新近系砂岩储层以原生孔隙为主，其次为胶结物溶孔和碎屑颗粒溶孔，次生孔隙仅在有限程度上改善了砂岩的储集性质。因此研究砂岩储层的原生孔隙的发育规律是比较重要的。（3）压实作用的差异是造成储集性质变化比较大的主要因素，其次为胶结作用。压实作用的大小受到埋藏深度和岩性的影响，也与储层所经历的埋藏方式有关。本区砂岩储层中的胶结物以方解石和硬石膏为主，也见少量方沸石。不同层段砂岩中的碳酸盐胶结物含量为4.0%～16.0%，局部地区硬石膏胶结物含量可达11.5%～28.0%，成为影响储集性质的主要因素。

Sandstone reservoirs of the Paleogene and Neogene in southwestern Qaidam Basin

 On the basis of petrologic study of about 40 wells, this paper expounds the characteristics of the Paleogene and Neogene sandstone reservoir in southwestern Qaidam Basin： (1)The rock composition of sandstone reservoir varies regularly in space-time. The compositional maturity and textural maturity of sandstones located in both sides of southeastern and northwestern in the study area are obviously lower than that located in the middle area. The compositional maturity and textural maturity of sandstones decline gradually from Paleogene to Neogene. This is accordance with the fact that the regional tectonic activity in the study area was enhancing from early to later. The variation of sandstone reservoir petrology affects its reservoir quality clearly, and then it makes the sandstone reservoir quality in both sides of southeastern and northwestern in the study area getting worse. (2) Primary pore is mainly types of pore in sandstone reservoir. Fore-researchers have different views on the pore types of sandstone reservoir, it is mostly believed that the main types of pore is secondary pore, especially in lower Ganchaigou formation, mainly developed secondary pore. The sandstone reservoir of Paleogene and Neogene is mainly for primary pore, and next for cement dissolution pore and rock debris dissolution pore, and secondary pore only improve the sandstone’s reservoir quality limitedly. So research for development regularity of primary pore in sandstone reservoir is more important. (3) The chief factors resulting in reservoir quality change are mainly due to the difference of compaction, and then to the cementation .The compaction degree is affected by buried depth and rock property, and also related to the buried way undergoing by the reservoir. The cementation in sandstone reservoir is mainly carbonate and anhydrite and fewer analcite. The content of carbonate cements varies between 4.0% and  16.0% in different layers., locally the content of anhydrite cement may be up to 11.5% to 28.0%, and it becomes primary factors affecting the reservoir quality.