川中龙岗地区沙溪庙组沙一段优质储层特征及主控因素研究

Characteristics and Main Controlling Factors of High-Quality Reservoirs in the 1st Member of Shaximiao Formation, Longgang Area, Central Sichuan

摘要: 川中北部龙岗地区中侏罗统沙溪庙组沙一段是四川盆地重要的致密砂岩油产区，但由于埋藏深度大，成岩作用复杂，勘探开发难度较大。本次运用测井分析、铸体薄片观察、岩心观察、X衍射分析、扫描电镜等实验分析方法，对沙一段优质储层的基本地质特征进行了分析，探讨了优质储层形成主控因素，对研究区后期致密油的勘探具有重要意义。研究表明：1) 研究区沙一段主要为一套三角洲平原沉积，岩石类型为长石岩屑砂岩为主，储层空间发育残余原生粒间孔、粒间溶孔、粒内溶孔和微裂缝，孔隙度和渗透率分布范围较广，整体较为致密。2) 沙一段优质储层发育的主控因素是沉积相、成岩相、和裂缝等。分流河道和河口坝沉积微相是优质储层发育的基础；压实相、胶结–压实相和胶结相对储层起破坏性成岩作用，而溶蚀相则有利于次生孔隙的形成；裂缝有利于油气运移，进一步改善了储层渗透率，对优质储层的形成至关重要。

Abstract: The first member of Shaximiao Formation of Middle Jurassic in Longgang area of North Central Si-chuan is an important tight sandstone oil producing area in Sichuan Basin, but it is difficult to ex-plore and develop because of its large burial depth and complex diagenesis. This paper analyzes the basic geological characteristics of the high-quality reservoir in Shaximiao formation by using the experimental analysis methods such as well logging analysis, casting thin section observation, core observation, X-ray diffraction analysis and scanning electron microscope, and probes into the main controlling factors for the formation of the high-quality reservoir, which is of great significance for the exploration of the tight oil in the later stage of the study area. The results show that: 1) The first member of the Shaximiao Formation in the Longgang area is mainly composed of a set of delta plains. The rock type is mainly feldspar lithic sandstone. The reservoir space develops residual primary intergranular pores, intergranular dissolved pores, intragranular dissolved pores and micro-cracks. The distribution range of porosity and permeability is wide, and the whole is relatively dense. 2) Sedimentary facies, diagenetic facies and fractures are the main controlling factors for the development of high-quality reservoirs in the first member of Shaximiao formation. The diversion channel and the estuary dam sedimentary microfacies are the basis for the devel-opment of high-quality reservoirs; the compaction phase, the cementation-compaction phase and the cementation phase both destroy the reservoir, while the dissolution phase facilitates the for-mation of secondary pores and improves the physical properties of the reservoir; fractures are conducive to the migration of oil and gas, further improving the permeability of the reservoir, which is crucial to the formation of high-quality reservoirs.