Apparatus for treating rock surrounding a wellbore

An apparatus for treating rock surrounding a cased well-bore, comprising:

• a hollow elongated housing;
• a plurality of nozzles radially arranged in said housing, and being mounted therein for free reciprocating movement from the center portion of said housing to the periphery thereof so as to project exteriorly of said housing;
• each said nozzle having a through passage communicating with the internal space of said housing for a flow therethrough of an abrasion laden fluid;
• said nozzles having their end portions facing exteriorly of said housing and being adapted to closely fit the casing wall, each said through passage of said nozzles having a larger diameter portion adjacent to said end portion;
• each said nozzle having additional passages one end of which communicating with said larger diameter portion of said through passage and the other end communicating with the space exteriorly of said nozzle, and said additional passages being adapted to provide an outflow of the abrasion laden fluid from the space defined by said larger diameter portion of said through passage and the adjacent casing wall, as said nozzles are pressed against said casing wall by said fluid;
• whereby said nozzles generally protect said casing from being washed away by said abrasive fluid, and enables perforating an opening in said casing of a diameter equal to about the diameter of said larger diameter portion and also provides where applicable for the utilization of substantially all of the kinetic energy of the flowing abrasive fluid for hydrofracturing of a formation without the need of packers.