Abstract: A hydrocarbon producing well is treated by first igniting a gas generating charge in the well to clean out perforations communicating between the casing and the formation without creating high permeability channels adjacent the perforations or fracturing the formation in a macroscopic sense. Then, a treatment liquid is injected into the wells by a gas generating propellant charge placed in the production string and then ignited. The propellant charge is designed to produce a minimum horsepower sufficient to push the liquid more-or-less equally through all of the open perforations. The propellant charge is designed to produce a maximum horsepower which is less than what is necessary to fracture the formation. Basically, the combustion rate of the propellant charge is reduced by one of a multiplicity of techniques to produce a long, relatively slow combustion rate.

Abstract: An explosive or combustion actuated subsurface well tool includes a firing head for initiating operation of the tool in response to a projectile, such as a ball or go-devil, being pumped down a tubing string extending from the surface. The firing head includes a passage sized to closely receive the ball or go-devil, in either a sealed manner in which substantially no liquid leaks around the pumped projectile or in an unsealed manner in which a small amount of liquid leaks around the projectile. As the projectile moves into the passage, the pressure drop across the projectile becomes quite large creating a large force sufficient to shear a safety pin, drive home a firing pin or otherwise initiating operation of the subsurface well tool.