Compression characteristic distribution and anisotropic evolution of shale fracture with shale self-supporting particles
HUANG Ting
ZHAI Cheng
LIU Ting
SUN Yong
ZHENG Yangfeng
CHEN Aikun
XU Hongyang
LAI Yongshuai
Abstract：The in-situ methane deflagration fracturing technique utilizes the collaborative combustion and explosion of in-situ desorbed methane and oxygen to produce high-temperature and high-pressure gases that effectively fracture shale reservoirs.During the fracturing process,some shale debris particles are generated around the fracture,providing a degree of self-support to the fracture channels.Among these,the understanding on the compressive closure behavior and fracture aperture evolution of shale fractures with shale debris particles is a critical research focus.This study focused on four types of specimens:Parallel Bedding Unsupported(PBU),Parallel Bedding Self-Supported(PBS),Vertical Bedding Unsuppor-ted(VBU),and Vertical Bedding Self-Supported(VBS).Employing a non-contact full-field strain measurement device,the authors investigated the influence of self-supporting particles and bedding on the distribution of compression behavior and anisotropic characteristics for shale fracture during stress loading.The results revealed that all specimens can be di-vided into four typical regions along the loading direction:the fracture zone,near-matrix zone,far-matrix zone,and no-im-pact zone.In each region,the vertical displacement exhibits a linear decreasing trend along the loading direction,with de-creasing rates in sequential order and approaching zero in the no-impact zone.Self-supporting particles mitigate the influ-ence of bedding orientation on the distribution of fracture compression characteristics along the fracture direction.The compressible and incompressible components of self-supported fractures are 47-56 times and 11 times that of unsuppor-ted fractures,respectively.Meanwhile,the proportion of compressible component of fracture aperture in self-supported fractures is 4-5 times greater than that in unsupported fractures.The Bedding Anisotropy Index(IBA)was introduced to quantitatively analyze the impact of self-supporting particles on the anisotropic evolution characteristics of shale fractures.During the stress loading process,all specimens sequentially experienced four phases:the IBA descent zone,IBA steep in-crease zone,IBA oscillation zone,and IBA stabilization zone.Self-supporting particles reduced the extent of the IBA oscilla-tion zone to(1-5 MPa)and increased the IBA stabilization value to 5.6,eliminating the differences in IBA stabilization val-ues among different bedding orientations.
Keywords：shale fracturecompression characteristicanisotropyshale self-supporting particlesfracture aperturede-flagration fracturing
Publication Date：2023-12-28
Online Publishing Date：2025-08-15(First online date of this platform, not the publication date of the document)
Pages：16( 4336-4351 )