Abstract: An apparatus for treating rock surrounding a wellbore comprises a hollow elongated housing having nozzles radially mounted therein, which are projectable externally thereof. Each nozzle has a through passage communicating with the internal space of the housing to pass the flow of a fluid with an abrasive filler therethrough. The external end faces of the nozzles are shaped so as to press against the wall of the casing. Each through passage of the nozzle has a larger-diameter portion at the end thereof, facing the casing wall. The body of each nozzle has auxiliary passages, each such passage having one end thereof communicating with the larger-diameter portion of the through passage and the other end thereof communicating with the space externally of the nozzle, the auxiliary passages affording the flow of the fluid with the abrasive filler from the space defined by the said larger-diameter portion of the through passage and the adjacent casing wall, as the nozzle is closely pressed against the casing.

Abstract: A system for developing or cleaning a screened well using dual concentric drill pipe. A blind annulus injection sub and a development head are interconnected with the drill pipe and so constructed that compressed air passing down the inner pipe is directed through nozzles in the head to agitate formation water and clear the screen. When air is passed down the pipe annulus it is injected into the inner pipe and causes formation water and sand to be drawn into the head and airlifted to the surface through the inner pipe.

Abstract: A method of in situ gasification of coal includes the steps of releasing reactant materials in a coal bed in a manner such that the reactants are directly exposed to the burning face of a coal bed under preselected temperatures and pressures whereby the incomplete combustion of the coal is affectively controlled. In one preferred form of the method, the heat generated from the combusted materials is captured and separated from the recovered gas so that the heat can be converted to other forms of energy separately from the recovered gas.

Abstract: A self-decentralized hydra-jet tool for jet treating the face of a formation penetrated by a well bore which tool includes a jet treating head assembly adapted to be lowered into a well bore and supported therein by a flexible conduit assembly communicating between the jet treating head assembly and a source of pressurized treating fluid, the jet treating head assembly including a plurality of jet nozzles therein arranged such that a force imbalance is imparted to the jet treating head assembly by the reaction forces resulting from the jet action of the nozzles thereby urging the jet treating head assembly into close proximity to the formation face being treated.