Yongming Yang

Effects of Pore Structures on Static Mechanical Properties of Sandstone

AbstractThis paper presents a numerical and experimental investigation on the effects of pore structures on the static mechanical properties of porous sandstone. Three-dimensional (3D) numerical models of porous sandstone with different statistical pore parameters are constructed using a software program and the experimentally acquired data of the parameters. The mechanical properties of sandstone are numerically tested using Brazilian disc split tests to probe the influences of pore structures. A number of physical models having similar statistical characteristics of pores and physical properties with those of the numerical models are produced using modeling materials. Brazilian disc tests and computer tomography tests are performed on the physical specimens with different porosities to clarify the responses of pore structures during failure processes. The numerical analysis implies that pores significantly affect the mechanical properties of porous sandstone such as stress concentration, distribution, a...

Adaptive Finite Element-Discrete Element Analysis for Microseismic Modelling of Hydraulic Fracture Propagation of Perforation in Horizontal Well considering Pre-Existing Fractures

Hydrofracturing technology of perforated horizontal well has been widely used to stimulate the tight hydrocarbon reservoirs for gas production. To predict the hydraulic fracture propagation, the microseismicity can be used to infer hydraulic fractures state; by the effective numerical methods, microseismic events can be addressed from changes of the computed stresses. In numerical models, due to the challenges in accurately representing the complex structure of naturally fractured reservoir, the interaction between hydraulic and pre-existing fractures has not yet been considered and handled satisfactorily. To overcome these challenges, the adaptive finite element-discrete element method is used to refine mesh, effectively identify the fractures propagation, and investigate microseismic modelling. Numerical models are composed of hydraulic fractures, pre-existing fractures, and microscale pores, and the seepage analysis based on the Darcy’s law is used to determine fluid flow; then moment tensors in microseismicity are computed based on the computed stresses. Unfractured and naturally fractured models are compared to assess the influences of pre-existing fractures on hydrofracturing. The damaged and contact slip events were detected by the magnitudes, -values, Hudson source type plots, and focal spheres.