柴北缘平台地区路乐河组砂岩储层特征

以重点钻井的岩芯样品和薄片的观察为基础,结合扫描电镜、X衍射、储层物性和压汞等化验资料的分析,对柴达木盆地平台地区路乐河组砂岩储层的物性特征及其主控因素进行了研究。结果表明路乐河组砂岩储层的岩石类型以岩屑砂岩和长石质岩屑砂岩为主,颗粒分选和磨圆中等-较差,成分成熟度和结构成熟度中等-较低;储层物性表现为以中孔-中渗为主,低孔-低渗为辅的特征,且孔隙度和渗透率相关性好;原生粒间孔是最主要的孔隙类型,约占70%,其次是粒间溶孔和粒内溶孔。压实作用和胶结作用分别减少了路乐河组砂岩储层原始孔隙的31.8%和29.5%,是其物性条件变差的最主要因素。在成岩演化早期阶段,碳酸盐胶结物增强了储集岩的抗压实能力,有效抵御压实作用在成岩阶段早期对储集岩粒间孔隙的破坏;在成岩演化晚期阶段,碳酸盐胶结物又为溶蚀作用提供了空间和物质基础,形成部分次生溶蚀孔隙,对平台地区路乐河组储层的物性又有一定程度的改善。

Reservoir Characteristics of the Lulehe Formation in the Pingtai Area of northern Qaidam Basin

Based on the observation of drilling core samples and thin sections, the physical property and influencing factors of sandstone reservoir of Lulehe Formation in the Pingtai region of Qaidam Basin were studied. Scanning electron microscopy, X-ray diffraction, reservoir properties and mercury injection and other information were mainly applied on this study. The result shows that the sandstone reservoirs of Lulehe Formation are mainly composed of lithic sandstone and feldspar lithic sandstone, with medium or low compositional maturity and textural maturity. Particle sorting and rounding are medium and poor. The performance of reservoir properties includes two major types:medium pore and permeability, low pore and permeability. Meanwhile, the correlation of the porosity and permeability is good. Pore type is primary intragranular pore, followed by a small amount of intergranular and intragranular dissolved pore. The original porosity of the reservoir were reduced by 31.8% and 29.5%, respectively, by compaction and cementation, which was the main factor for porosity-losing processes. Meanwhile carbonate cements has enhanced the ability of the resistance to compaction of reservoir rock. Therefore, it can effectively prevent compaction damage to the intergranular pore of reservoir rocks in the early diagenetic stage. Moreover, it provides space and material basis for the corrosion and dissolution of acidic fluid, which is beneficial to the formation of secondary corrosion pores and the improvements of reservoir properties.