Model Investigation of Wellbore Pressure Distribution in Stem-Induced Fracturing

Summary This paper describes model testing conducted to investigate pressure variations along the length of a wellbore between a decoupled bottom charge and the stem. Tests were conducted in three-dimensional models made from thick plexiglass sheets that contained small decoupled explosive charges in the bottom of the borehole. Charge sizes varied from 75 to 200 mg, and the open borehole length between the top of the charge and the stem ranged from three to seven times the charge length. Both top and bottom charge initiations were investigated. Multiple pressure transducers were used along the borehore, and pressure/time distributions were determined at several locations. An additional series of tests is described in which the borehole geometry was altered by varying the diameter of an orifice plate placed in the wellbore. The use of this orifice plate was demonstrated to be effective in controlling the increase rate of the pressure pulse at the stem location.