Appts. for treating rock surrounding a well bore - has axially floating nozzles for engaging and forming perforations of predetermined size in well casing

摘要

Appts. for treating rock surrounding a cased well bore includes an elongate hollow housing carrying a set of radically-oriented nozzles, each communicating with the interior of the housing to receive abrasive-laden fluid supplied to the housing. Each nozzle is slidably supported by the housing so that it is pressed into contact with the casing under the influence of the fluid and its central flow passage is enlarged adjacent its downstream end. Each nozzle also has branch passages communicating with the enlarged portion of the central passage and opening to the exterior of the nozzle. Fluid initially supplied to the nozzles escapes into the well bore via the branch passages but erodes the areas of the casing isolated by the outer ends of the nozzles to form perforations of a dia. equal to that of the enlarged portions of central passages of the nozzles. Once the perforations have been established, fluid subsequently supplied to the nozzles enters the surrounding rock to effect the desired treatment, e.g. fracturing and acidising. Appts. provides for formation of perforations of a predetermined size, which ensures that virtually the entire kinetic energy of the treatment fluid is available for forming fractures.