雅布赖盆地新河组块状砂岩沉积–成岩–物性耦合机制

Coupling Mechanism of Sedimentation-Diagenesis-Physical Property from Xinhe Formation Massive Sandstones in Yabrai Basin

摘要: 雅布赖盆地新河组块状砂岩的孔隙度与渗透率交会图呈现出特殊的“两竖夹一横”特征，通过岩心观察、物性、铸体薄片、扫描电镜等开展沉积–成岩–物性耦合机制研究以查明孔隙度与渗透率相关性差的根源。结果表明，3种沉积–成岩–物性耦合机制形成了7类砂岩是雅布赖盆地新河组块状砂岩物性复杂的根源。高粘滞性砂质碎屑流沉积物在压实作用下形成I类低孔低渗砂岩，低粘滞性砂质碎屑流沉积物在伊利石晶间孔和方解石溶蚀孔的共同作用下形成II类中孔中渗砂岩，颗粒流沉积在方解石胶结物和碎屑长石差异溶蚀作用下形成了III类低孔低渗砂岩、IV类中孔中渗砂岩、V类高孔中渗砂岩、VI类高孔中渗砂岩、VII类高孔高渗砂岩。孔隙度与渗透率交会图中，“左下竖”由I和III类砂岩构成，“右上竖”为VII类砂岩，“一横”由II类和IV~VI类砂岩组成。沉积作用是砂岩物性差异的内在因素，而成岩作用是砂岩物性差异的直接原因，二者共同作用是雅布赖盆地新河组块状砂岩孔隙度和渗透率相关性复杂多变的根源。

Abstract: Based on core observation, physical property, casting thin section and SEM, coupling mechanism of sedimentation-diagenesis-physical property from Xinhe Formation massive sandstones in Yabrai Basin was investigated, in order to discover the root of the poor correlation between porosity and permeability whose crossplot exhibits the complex “two vertical sections clamping one horizontal section” feature. The result shows that 3 kinds of the coupling mechanisms of the sedimentation-diagenesis-physical property control the development processes of 7 types of massive sandstones and this fact is the root of the complex physical property from Xinhe Formation massive sandstones in Yabrai Basin. The high viscous sandy debris flow sediment forms the type-I low porosity and permeability sandstones under compaction. The low viscous sandy debris flow sed-iment with intergranular pore of illites and calcite dissolved pores becomes the type-II middle porosity and permeability sandstones. By the differential dissolution of the calcite cement and feldspar, the grain flow sediment evolves to the type-III low porosity and permeability sandstones, type-IV middle porosity and permeability sandstones, type-V high porosity and middle permeability, type-VI high porosity and middle permeability and type-VII high porosity and permeability. In the crossplot of the porosity and permeability, its left lower vertical section consists of the type-I and type-III sandstones, the right upper vertical section is type-VII sandstones, and the middle horizontal section is composed of the type-II sandstones and type-IV to type-VI sandstones. The root of the poor correlation between porosity and permeability is attributed to the sedimentation and diagenesis, of the two, the former is the internal factor of the poor physical property, and the latter is the direct cause of the poor physical property.