Title of Paper:储层砂岩破坏特征与脆性指数相关性影响的试验及数值研究

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Date of Publication:2022-10-04

Journal:岩石力学与工程学报

Affiliation of Author(s):建设工程学部

Volume:36

Issue:1

Page Number:10-28

ISSN No.:1000-6915

Abstract:Failure characteristics and brittle evaluation of reservoir sandstone
   are of great significance in oil and gas drilling engineering. The
   sandstone cores from the well of Shengli Oil Field were studied with the
   developed physical tests under condition of triaxial compression and
   numerical simulation. The results show that the failure mode of
   interlayer and reservoir cores under the effect of confining pressure is
   mainly the shear failure. Under the same level of confining pressure,the
   interlayer cores are more brittle than reservoir cores. The brittleness
   tendency can be evaluated by the brittleness index B effectively.
   Besides,the relevance between the main mechanical parameters of
   sandstone and the brittleness index B is analyzed as well. Under the
   condition of the same confining pressure,the peak strength,expansion
   point,elastic modulus,Poisson￠s ratio,residual strength and residual
   strength coefficients of cores decrease with the increase of brittleness
   index B. The relationship between index B and parameters is linearly
   fitted well. The intrinsic factor of low brittleness is the high clay
   mineral content of the oil layer rock. The microscopic brittle
   characteristics of two kinds of sandstone are shown in the CT scans
   under uniaxial compression. In the case that other parameters are
   fixed,the numerical cores are more brittle with the increase of the
   elastic modulus,ratio of compressive strength to tensile strength and
   internal friction angle. However, the brittleness of cores reduces with
   the increase of Poisson's ratio,residual strength and residual strength
   coefficient. In addition,there is little relationship between the
   brittleness of cores and its strength. The modes of acoustic emission
   are dominant by the pre-main-after shocks and group shocks. The
   essential relationship between the index B and the acoustic emission
   modes is summarized based on the results of physical experiment and
   numerical calculation. Under the condition of same loading rate,the
   acoustic emission modes in the low brittleness zone,middle brittleness
   zone and high brittleness zone are swarm shocks,pre-main-after shocks
   and mass shock. Lastly,the mechanism of acoustic emission modes was
   verified with those of limestone and different types of coals.

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