A study on bond breakage behavior of weak Cretaceous Kazakhstani reservoir sandstone analogue

Abstract

The study examines the effect of cement bond breakage in the mechanical behavior of porous weak sandstones in Kazakhstan’s oil fields using one-dimensional compression, triaxial shearing apparatuses, and Discrete Element Method (DEM) numerical simulation. Analogue sandstone materials were prepared by cementing a sand material with similar mineralogy to the real reservoir with the sodium silicate solution. The results of the cemented sandstones were compared to the results of the uncemented sand, disaggregated sandstone and silty sand of similar particle size distribution to understand the effect of the cemented structure. The failure behavior of the material was investigated in the experimental and numerical studies at different confining pressures and it was found that the behavior is mainly controlled by the cement bonds as there is no major change in the particles during the tests. It was found that the plastic yielding condition is mainly associated with the breakage of the cement bonds and this gives rise to volume compression and strain hardening of the material. The DEM results provide further confirmation that the degradation of the specimen stiffness is directly related to the bond breakage initiation and higher confining pressures affect the breakage rate and weaken the effect of the cemented structure, which is compensated by a stronger role for the frictional resistance between sand particles.