Abstract: Subterranean mineral seams, such as coal, which have been penetrated by gas production wells are stimulated to produce additional gas by placing a liquid, such as a solvent for coal, in the wellbore and in communication with a tubing extending within the wellbore and having a frangible shear disk assembly disposed therein. Pressure is increased inside the tubing string by pumping gas and/or liquid into the tubing string in sufficient quantity to cause the shear disk to release fluid pressure to act on the fluid in the open hole wellbore portion so that a substantial pressure pulse is exerted on the coal seam to effect rubblization of the coal to form a cavity and release entrapped or adsorbed gas for production up through the well. Imposition of rapid and cyclic pressure pulses on the coal seam at pressures up to 5000 psi above the in situ stress improves production of gas therefrom.

Abstract: Hydraulic fractures are initiated or extended into fluid-producing earth formations from a cased well by filling a space within the casing adjacent the formation zone of interest with liquid which extends into a tubing string and forming a pressure gas charged portion of the tubing string by introducing pressure gas or liquid into the tubing string to compress a column of gas therein to a pressure which exceeds the formation fracture breakdown pressure. By perforating the casing or, if perforations already exist, releasing a frangible disk type closure interposed in the tubing string, the gas charge in the tubing string forces fluid into the formation at sustained pressure and flow conditions not attainable by surface pumped fracture fluids.