准噶尔盆地下二叠统风城组致密碎屑岩储层发育特征

摘要

准噶尔盆地西北缘乌尔禾—夏子街地区下二叠统风城组发育了典型的致密碎屑岩储层。综合地质和地球物理资料，研究了该区储层发育特征。结果表明风城组沉积早期和晚期扇体规模相对较大，零星分布有小规模的滑塌浊积扇和滩坝砂体。风城组沉积中期，湖盆水体扩张，扇体不发育。滩坝砂岩物性好于扇三角洲前缘砂体，好于浊积扇。高成熟度的砂砾岩为优质储层（岩相）。岩石组分中的火山物质影响储层的成岩演化，进而影响储层质量。塑性的凝灰岩屑降低抗压实能力；凝灰岩屑在埋藏过程中水解、蚀变，析出不同自生矿物，破坏孔隙；长石、岩屑、基质和各种自生矿物溶蚀，一定程度上增加孔隙。风城组碎屑岩储层整体为低孔、低渗的致密砂岩储层，“甜点”发育受多因素复合控制，包括沉积相带、岩石组分、粒度、成熟度、溶蚀作用的发育程度等。%Typical tight clastic reservoirs were developed in the Lower Permian Fengcheng Formation in Wu-Xia area in the northwestern margin of the Junggar Basin. Based on the geological and geophysical data, the reservoirs′ characteristics have been studied. The results show that the fans are relatively large during the early and late periods of the Fengcheng Formation, with small-scale slump turbidite fans and shoal-bar sand bodies sporadically distributed. The water bodies expanded and the fan bodies were not developed in the middle stage of the Fengcheng Formation. The physical properties of shoal-bar sandstones are better than those of the sandstones of fan delta front and turbidite fans. Glutenites with high maturity are high-quality reservoir rocks. The volcanic materials in the rocks had an impact on the reservoir diagenetic evolution, thereby affecting the reservoir quality. The plastic tuff debris reduced the compressive strength; the tuff debris were exposed to the hydrolysis and alteration during the burial process, precipitating different minerals, which destroyed the porosity;the dissolution of the feldspar, rock debris, matrix and various authigenic minerals increased the porosity to some extent. The clastic reservoirs in the Fengcheng Formation are overall tight sandstones with low porosity and permeability, and the development of“sweet spots”are under the compound control of many factors, including the sedimentary facies, rock components, particle sizes, maturity, and the development of dissolution.