东濮凹陷上古生界致密砂岩优质储层发育特征及主控因素

文章探讨了东濮凹陷上古生界砂岩优质储层形成的主控因素，为预测优质储层提供依据。文章以东濮凹陷庆古3井为主要研究对象，通过岩心观察、铸体薄片、XRD、核磁共振冻融法及三束离子抛光—场发射扫描电镜联用等综合分析，研究了东濮凹陷二叠系储层发育特征及控制因素。研究表明：东濮凹陷上古生界砂岩以岩屑长石和长石岩屑砂岩为主，孔隙度值介于0.2%~12.8%，渗透率值介于0.0016~5.7 mD，属于特低孔致密型储层。溶蚀残余粒间孔、粒内溶蚀孔、晶间孔是东濮凹陷主要发育的孔隙类型，储集空间都是次生成因，各层段几乎未见原生孔隙留存，裂缝相对不发育。次生孔隙主要由长石颗粒和岩屑（包括凝灰质）溶蚀形成，在石千峰组和下石盒子组储层中较为常见。优质储层受沉积相、岩性和成岩作用的控制，石千峰组砂岩属于内陆河流相沉积，砂体发育，是东濮凹陷上古生界最有利的储集层系，长石的溶蚀是石千峰组优质储层形成的主要控制因素。下石盒子组属于三角洲沉积，由于沉积时期火山作用，导致大量的凝灰质沉积，凝灰质蚀变形成的高岭石晶间孔是该层储层形成的重要机制。山西组主要三角洲沉积，也是主要成煤期，煤系酸性流体导致溶蚀，但强烈的石英次生加大使砂岩致密化。

Characteristics and Main Controlling Factors of High-quality TightSandstone Reservoirs in the Upper Paleozoic of Dongpu Depression

Studying the main controlling factors of the formation of high-quality sandstone reservoirs of the Upper Paleozoic in Dongpu Depression can provide a basis for predicting high-quality reservoirs. This paper focuses on the Q3 well. Through comprehensive analyses of core observations, casting thin section, XRD, nuclear magnetic resonance cryoporometry and TIB-field emission scanning electron microscopy, the characteristics and controlling factors of the Permian reservoir in Dongpu Depression were studied. The results show that the Upper Paleozoic sandstone in Dongpu Depression is dominated by lithic feldspar and feldspar sandstones, the porosity is 0.2%-12.8% and the permeability is 0.0016-5.7 mD, which belongs to the ultra-low porosity reservoir. The residual intergranular pore, intragranular dissolution pore, carbonate mineral intergranular pore and clay mineral intergranular pore are the main pore types. Secondary pores were mainly formed by the dissolution of feldspar particles and cuttings (including tuff), which are more common in the reservoirs of P2sh Formation and P1x Formation. The high-quality reservoir is controlled by sedimentary facies, lithology, and diagenesis. The sandstone of P2sh Formation belongs to the inland river facies, the river bed is widely distributed and the sand body is developed. It is one of the most favorable reservoir system in the Upper Paleozoic of Dongpu Depression. The dissolution of feldspar is the main controlling factor of the formation of high-quality reservoir of P2sh Formation. The P1x Formation belongs to delta deposition, which was caused by volcanic activity during the sedimentary period, resulting in a large amount of tuff deposition. The kaolinite intergranular pores formed by erosion of tuff is an important mechanism for the formation of this reservoir. The main delta deposits in P1s Formation are also the main coal forming period. The acid fluid of coal system leads to the dissolution, but the large secondary increase in quartz makes the sandstone dense.