An experimental study to investigate the effect of mineral composition on mechanical properties of shale gas formations

Hydraulic fracturing is well-known stimulation technique to extract unconventional shale gas. This technique is however highly dependent on the mechanical properties of the shale reservoir that is expected to be significantly varied with their rocks' mineral composition. This study has therefore been aimed to examine the effect of various rock minerals on mechanical properties of shale formations through conducting a comprehensive experimental program. In order to replicate the composition of shales found in different regions, reconstituted specimens were produced from powdered minerals (quartz, feldspar, calcite, dolomite and kaolinite) with different compositions. Reconstituted specimens were tested for unconfined compressive strength (UCS) and splitting tensile strength after curing for 14 days. 38mm diameter and 76mm length specimens were used for the UCS tests, and 19mm diameter and 38mm length specimens were used for the splitting tensile strength. Findings from this study indicate increasing trend of UCS with the increasing of kaolinite and calcite percentages. Same kind of relationship was observed for the splitting tensile strength as well. Moreover, results show an increasing trend of UCS with increasing density. Interestingly, results indicate a decreasing trend of UCS with the increasing of quartz percentage, which was not expected in this study.