柴达木盆地柴西南区碎屑岩储层形成的主控因素分析

运用大量的岩矿分析测试资料系统地研究了柴达木盆地柴西南区碎屑岩储层性质的控制因素,指出沉积环境、岩石学特征、埋藏成岩史、异常高流体压力和盐湖水介质环境是控制储层成岩演化和储集性质的主要因素。该区广泛发育的三角洲平原和前缘的分流河道及滨湖砂坪微相砂岩是优质储层发育的基本条件。储层碎屑组分中的塑性颗粒含量和粒径是储层性质的重要控制因素;成岩作用是储层性质的决定性因素,其中压实作用对储层性质的影响最大,胶结作用仅在局部地区成为重要的控制因素,溶蚀作用的影响是比较有限的。而储层的压实作用主要受储层岩性、成岩胶结强度、埋藏史和地层流体压力等4个因素的控制。岩性是通过储层中塑性岩屑含量随粒径的变化以及不同粒级的储层具有不同的抗压性等两方面表现出来的,成岩期胶结物的发育可以使储层的压实作用明显减弱,埋藏史可以造成储层性质的较大差异,而高压地层流体压力可以有效地抑制压实作用的进行。

Analysis of the Main Controlling Factors on the Formation of Clastic Reservoirs in the Southwestern Area of the Qaidam Basin

Based on a great deal of analytical data of rock and mineral, discussed, the controlling factors on clastic rock reservoir property in the southwest area of the Qaidam basin are the sedimentary environment, lithological characteristics, buffed history, unusual high fluid pressure, salt lake environment were main factors deciding reservoir diagenetic evolution and reservoir property. The widely developed sandstones of the shore sand platform, the delta plain and delta front are a basic condition for the development of excellent reservoirs. The content and size of the plastic grains in the reservoir clasts are important factors controlling the reservoir property. Diageneses are a crucial factor of reservoir property, in which consolidation heavily affected reservoir property, cementation was only an important controlling factor influencing reservoir property in the partial area and the influence of dissolution was weak. Consolidation of reservoir is controlled by four factors, i. e. , hthological characteristics, strength of diagenetic cementation, buffed history, and strata fluid pressure. Lithology was reflected by the change of the content of plastic rock clasts with grain size and different anti-pressure of reservoir with different grain size. Development of diagenetic cements weakened consolidation of reservoir, buffed history differed reservoir property and high fluid pressure effectively restrained consohdation.