Experimental investigation of the hydro-mechanical behavior of tight gas formation sandstone and its impacts on the wellbore stability

The tight gas formation sandstone in North Germany with a permeability below 0,6 mD is characterized by an unknown Biot’s and Skempton’s coefficient, which are the hydro-mechanical coupling parameters to decide whether the under-balanced drilling (UDB) could be used. This two coefficients and the sandstone strength are determined by laboratory experiments. Based on the experimental results and on theory of poroelasticity as well as on the parameter variation analysis, the range of minimum mud density is determined for a vertical and horizontal wellbore in the tight gas formation sandstone.