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<br /> <br />..~r - <br />.,,, ~ <br />:.,\ , <br />Figure 4, Progression o(Ca•~i[y Washing by Floar[ng String Technique. <br />~~:: Stage 2. <br />~. <br />I~ <br />~i <br />ii <br />i <br />i ;Stage <br />I. <br />Inert <br />Blanket <br />''; + Stage <br />~:: \ 3. <br />\~:::. <br /> <br />~~ ; <br />Ftgure 5. Cavity Progression Usinj Concentric Strings ro Minimize Pipe hlaniputation. <br />Stationary Pipe Technique <br />This technique consists of keeping the number of pipe manipulations to a minimum and mov- <br />ing only the inert blanket to achieve control. Both the tubing and casing are positioned only once <br />for a given series of stages. Due to the physical set up of the circulation system, gravity segre- <br />gation is not as pronounced as in the previous method and cavity progression is more cylindrical. <br />However, enough divergence is achieved in the upper regions of the cavity to facilitate the forma- <br />tion of spherical shapes. Figure 6 shows the technique and type of cavity formation obtained. <br />The desirable feature of this type operation is that it facili[ates the formation of various cir- <br />culation patterns within the cavity by simplifying operational func[ions identified with pipe manipu- <br />lations. The undesirable feature of the interdependence of washing stages is inherent in this pro- <br />cedure. Whereas this may be a dis[inct disadvantage when attempting spherical shapes, it may <br />not be detrimental when constructing cavities of less complex configuration. <br />301 <br /> <br />