Micromechanical characteristics and classification of the grains of lacustrine fine-grained sedimentary rocks:A case study of shales in the 7th member of the Upper Triassic Yanchang Formation,Ordos Basin
Fine-grained sedimentary rocks contain abundant hydrocarbon resources.To examine the microscopic structural and micromechanical characteristics of their grains,we explore such rocks in the 7th member of the Upper Triassic Yanchang Formation(also referred to as the Chang 7 Member)in the Ordos Basin.Using scanning electron microscopy(SEM)and nanoindentation experiments,we delve into the geometric characteristics and micromechanical properties of the grains of these rocks.The results indicate that based on five characterization parameters,namely grain size,flatness,angularity,hardness,and modulus of elasticity,the fine-grained sedimentary rocks in the Chang 7 Member can be categorized into six major grain types:grain size and angularity predominating;flatness and angularity predominating;flatness,angularity,modulus of elasticity,and hardness predominating;modulus of elasticity and hardness predominating;angularity,modulus of elasticity,and hardness predominating,and grain size,angularity,and modulus of elasticity predominating.Five types of grain assemblages can be further identified based on the relative contents of the six types of grains.Additionally,the coupling relationships between the grain types and mineral types of the fine-grained sedimentary rocks are determined.The proposed scheme for microscopic grain classification of fine-grained sedimentary rocks assists in understanding the microscopic structural characteristics of fine-grained sedimentary rocks and predicting the spatial distributions of geological sweet spots,thus holding great theoretical and scientific significance for the hydrocarbon resource assessment and efficient hydrocarbon exploitation of fine-grained sedimentary rocks.
scanning electron microscopy(SEM)nanoindentationclassification schemegrain of fine-grained sedimentary rockshalethe 7th Member of Yanchang Formation(Chang 7 Member)Ordos Basin
NETL
NSTL
万方数据
