青东凹陷沙河街组三、四段储层成岩作用及孔隙演化

DIAGENESIS AND POROSITY EVOLUTION OF RESERVOIR OF THE 3th,4th MEMBER OF SHAHEJIE FORMATION IN QINGDONG SAG

青东凹陷沙河街组三、四段的砂岩储层是渤海湾盆地内主要的油气储层之一,其储集岩主要为中—细粒岩屑长石砂岩、长石砂岩及长石岩屑砂岩,该砂岩储层具有中—高孔隙度、中—低渗透率的特点。在对该区沙河街组油气藏宏观沉积特征研究的基础上,结合岩石薄片(74块)、铸体薄片(78块)、扫描电镜(4块)及X射线衍射(77块)等微观分析,对其储层成岩作用的类型、成岩阶段的划分、孔隙演化模式的确定及对储集物性的影响进行了深入的探讨,认为研究区砂岩经历了压实压溶作用、胶结作用、交代作用、溶蚀作用、烃类侵位以及构造破裂等多重成岩作用的改造,已达到中成岩阶段B亚期。通过孔隙演化分析认为:压实压溶、胶结作用是储层原生孔隙减少、物性变差的决定性因素;而多期的溶蚀作用、环边绿泥石胶结、烃类侵位、构造破裂则有利于次生孔隙的形成,改善储层的储集性。

Sandstone in the 3rd and 4th Member of Shahejie Formation in Qingdong Sag is one of the main oil-gas reservoirs in Bohai Bay Basin. These reservoir rocks are medium to fine-grained Lithic-feldspar sandstone, feldspar sandstone and feldspar-lithie sandstone, with medium-high po-rosity,medium-low permeability. Based on the study of macroscopic depositional characteristics of the oil-gas reservoirs in the Shahejie Formation,various methods, such as rock thin section,cast thin section,scanning electron microscope and X ray diffraction,are used to systematically and thoroughly study the diagenesis types, the diagenesis stage division, pore evolution model determi-nation and its influences on the storage capacity. It is indicated that the sandstone went through the transformation of multiple diagenesis, such as compaction, pressure solution, cementation, metasomatism,dissolution, hydrocarbon emplacement and structure rupture. Now it is in the mid-dle diagenesis stage B period. Quantitative analysis of pore evolution shows that compaction,pres-sure solution and cementation are decisive factors reducing reservoir primary pores,lowering res-ervoir property. While the multiple stage dissolution, rim chlorite cementation, hydrocarbon em- placement, structure rupture are beneficial to secondary pore formation and improving the reser-voir quality.