Abstract:

With the development of mechanical testing technology in recent years， the nanoindentation， a technique wildly recognized in micro-fabrication materials research， has been introduced into shale study， and become an important tool to test the micro-mechanical properties of shale. At present， it has been one of the hot research topics to study the mechanical properties of shale from the microscopic perspective. In this study， we summarize the influences of shale sample preparation methods and nanoindentation test system on test results， elaborate the application of nanoindentation technique in micro-mechanical and creep rupture characterization of shale. The advantages and existing problems of this technique are thereby analyzed and discussed， while looking to its development trend. The results are shown as follows. First， the technique can serve for precisely characterizing the mechanical properties of the bulk shale and its matrix phases. Second， the micro-creep rupture behavior of shale can be obtained by studying the displacement-time curve during the loading stage， which is of significance to having an in-depth understanding on the creep rupture deformation mechanism of shale in micro view. Third， testing the evolution characteristics of micro mechanical properties of fluid/shale interactions can provide basic experimental data for actual hydraulic fracturing or supercritical carbon dioxide fracturing of shale. In all， the nanoindentation technique serves to get an even finer understanding of shale in micro level， which is conducive to analyzing the mechanical behavior of shale in essence， and provide theoretical basis more reliable for the exploration and development of shale gas.

Key words: test system, micro mechanical property, creep rupture behavior, fluid/shale interaction, nanoindentation, reservoir fracturing, shale