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TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractFor many years, various types of simple nozzles have been regularly used for wellbore cleaning with coiled tubing. This paper describes the advances made in fluid jetting technology, associated tools and the parameters that are crucial to the efficiency of these techniques. A laboratory and field testing programme has been completed and data is included. By detailed design of the internal fluid path, orifice geometry, jet stand off and pump rates, tool effectiveness has now been improved to a level several times more efficient than previously available for the same feed pressures and flow rates. Pre-engineering using computer simulation to optimise the job design parameters has proven essential in designing clean out jobs and sizing the appropriate coiled tubing and pumping equipment. Three distinct categories of tools have emerged; conventional drilled nozzles, non-rotating high-pressure nozzles and high pressure rotating tools. All three types have gained a common advantage from the development of a Downhole Phase Separator. The high-energy losses previously associated with a two-phase fluid necessary in low hydrostatic wells can now be eliminated. A step change in operational efficiency has resulted through combining the major improvements in jetting tool design with the ability to separate gas and liquid phases downhole. With this development, the full benefits of using single phase fluid jetting can be realised in low hydrostatic wells.

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