The manufacture, mechanical properties, and microstructural analysis of synthetic quartz-cemented sandstones

A key issue in the field of porous rock geomechanics is finding suitable suites of samples in which petrophysical characteristics systematically vary, in order to determine the controlling factors on the mechanical behavior. To resolve this problem a new methodology has been developed, whereby high-porosity synthetic sandstone samples are produced from initially incohesive sand, by using the chemical reaction between sodium silicate and hydrochloric acid to generate amorphous quartz cement and thus provide cohesion. This enables the production of sandstone samples for laboratory testing which have reproducible petrophysical properties that can be systematically controlled, including porosity, grain size, cement content, grain shape and grain size distribution. Here, poorly-sorted, high-porosity (36-38%) sandstones were produced and subjected to a range of geomechanical tests, including uniaxial and triaxial experiments, to see if their microstructure and mechanical response was similar to equivalent natural samples. The 36-38% porosity synthetic sandstones have realistic and reproducible uniaxial compressive and tensile strengths of 5.18 (+/- 0.76) MPa and 0.167 (+/- 0.117) MPa respectively, as well as hydrostatic yield strengths (P*) of 67-69 MPa. They also exhibit yield curves with a comparable geometry to natural sandstones of similar porosity and grain size and display elastic moduli within the expected range for natural sandstones. The methodology outlined in this contribution allows for the production of sandstones for laboratory testing with reproducible behavior, that can be utilized in future studies to systematically investigate how different petrophysical properties control the mechanical response of sandstone to elastic and inelastic deformation.

Automated summary

A new methodology has been developed to produce high-porosity synthetic sandstone samples with reproducible petrophysical properties, allowing for systematic investigation into how different petrophysical properties control the mechanical response of sandstone to elastic and inelastic deformation in future studies.