束鹿凹陷古近系沙河街组第三段下部储层物性及其影响因素

Physical properties and influencing factors of the reservoir rocks in the lower part of the third member of the Palaeogene Shahejie Formation in the Shulu depression

关键词:  束鹿凹陷|古近系|沙河街组|物性|影响因素

Key words:  Shulu depression|Palaeogene|Shahejie Formation|physical property|influencing factor

摘要:

本文在对束鹿凹陷古近系沙河街组第三段下部地层、岩性、沉积相、成岩作用、成像测井等方面进行深入研究的基础上,查明了研究区储层物性特征及其影响因素。指出研究区储层原生孔隙不发育,以孔隙-裂缝型储层为主,储集空间以次生溶孔和裂缝为主,渗滤通道主要是裂缝,属特低孔特低渗储层。研究区的储集层主要是重力流成因的各种砂砾岩体和混积成因的泥灰岩类,由于其特殊性,导致它既不同于一般的碎屑岩,也不同于正常沉积的碳酸盐岩,因此,影响其储集性能的因素较复杂,概括起来主要有岩性、厚度、沉积相、成岩作用、构造应力等对裂缝、孔隙度的影响。其中性脆、泥质砂的中薄层砂砾岩,即贫基质的碎屑流易形成裂缝,同时构造应力是导致裂缝形成的重要原因:而具塑性、泥质含量高、层厚的重力流沉积及泥灰岩沉积不易形成裂缝。而成岩压实和胶结是导致地层孔隙度减小的主要原因,溶解作用则形成次生孔隙。

Abstract:

The reservoir rocks in the lower part of the third member of the Palaeogene Shahejie Formation in the Shulu depression are characterized by less-developed original pores,dominant secondary solution openings and fissures with extraordinary low porosity and permeability.These reservoir rocks interpreted as pore-fissure reservoir rocks consist of sandstones and conglomerates of gravity flow origin and marls of mixed origins.The factors influencing the reservoir quality include lithology,thickness,sedimentary facies,diagenesis and tectonic stress.The fissures generally occur in the brittle medium to thin-bedded sandstones and conglomerates as the matrix-poor debris flow deposits with lower contents of mud and under the tectonic stress rather than in the plastic thick-bedded gravity flow deposits and marls with high contents of mud.The compaction and cementation during the diagenesis are responsible for the decrease of porosity,and the dissolution leads to the formation of secondary porosity in the reservoir rocks.