In a Gas Research Institute sponsored study, enhanced formation image analysis was performed on twelve wells in the Antrim Shale, Michigan Basin. The analysis revealed that the abundance of open and partially open fractures as well as their degree of interconnection are controlling factors in gas production. Borehole maps show the interconnection with reference to the borehole.
A fracture factor (Zf) was derived and plotted against gas flow rates for nine wells. Six wells treated with a singlestage stimulation show a linear relationship between (Zf) and Q. Two were stimulated with a two-stage treatment and produced more gas than single-stage wells with comparable values of Zf. The methods of fracture analysis derived for the Antrim Shale should have immediate practical application to other unconventional and tight reservoir rocks.