Abstract: Gas flow from a coal seam to a mine face in the seam is blocked by drilling a hole from the face into the seam in a direction generally parallel to the direction of the flow of the gas to be blocked; forming a notch at the interior end of the hole; injecting a fluid into the hole and notch under a pressure sufficient to hydraulically fracture the seam along a plane extending substantially perpendicular to the hole and to the direction of gas flow; and filling such fracture with a barrier-forming fluid. The hole is then plugged to prevent retrograde flow of the fluid to the mine face.

Abstract: The present invention relates to an improved method of solution mining potassium chloride from subterranean ore deposits containing both potassium chloride and sodium chloride. By the present invention, an aqueous medium is passed through the ore deposits so that potassium chloride and sodium chloride are dissolved therein. Magnesium chloride is combined with the aqueous brine solution formed so that an aqueous brine solution containing potassium chloride, sodium chloride and magnesium chloride in specific proportions is produced, and the solubility of potassium chloride in the solution is reduced. The combined aqueous brine solution is then concentrated so that it is substantially saturated with potassium chloride, and the concentrated solution is cooled to cause the precipitation of substantially pure potassium chloride.