will greatly increase the likelihood that a fracture will propagate from borehole 14 and intersect borehole 12 as desired it is not anticipated that any particular fluids are essential to the various steps of the process water would typically be used as the injected cooling fluid primarily because of its availability and low cost special hydraulic fracturing fluids may be used if desired during the fracturing step the fracturing fluid should for best performance be chilled well below ambient formation temperature fluid used for plugging or killing of blowout well 12 would typically be a heavy drilling mud as conventionally used for such purposes the process of the present invention may also be used for generating link channels between wells in other processes for example in coal gasification processes it is necessary to generate a link channel between adjacent injection and production wells before the main burn zone may be ignited it is known that fractures may be used to form such link channels by injecting a cold fluid for example water in the injection well below the fracturing pressure and producing it from the production well a cooled zone may be provided between the two wells as illustrated in the figures when injection pressure is increased to fracturing levels the cooled zone will tend to direct the fractures from the injection well to the production well for the same reasons described above when the fracture has been extended.