Coiled-tubing placement

Limited interval coverage can be overcome to a degree by maximizing matrix acid injection rate. Greater coverage can be accomplished with chemical diversion or, preferably, mechanical placement— including coiled-tubing/injection-nozzle methods. 

Mechanical placement with isolation packer systems allows for the injection of acid within a limited treatment interval at one time. Other treatment intervals within the total zone can be treated individually in stages. Figure 6-3 depicts the treatment of a bmited interval with coiled tubing through a packer setting. 

Importantly, in the extremely long horizontal completions that are popular today, mechanical placement (without coiled tubing) may be of limited value, if not totally ineffective. This is because the isolated interval length per stage may have to be too long for all practical purposes, as a result of the limit on settings (deflation/inflation cycles) that can be withstood. In such cases, it is sometimes possible—and even desirable—to combine mechanical placement with chemical diversion methods. 

Low-strength HCl/flexible strength HF (up to 6%) + organophosphonic acid complex, using coiled-tubing/jetting-nozzle placement and/or on-the-fly chemical diversion... 

Coil configuration. The relative orientation of the highband and broadband coils with respect to their placement around the sample-containing NMR tube. A normal coil configuration locates the broadband coil closer to the sample, while an inverse configuration locates the highband (normally tuned to H, but possibly F) closer to the sample. 

Since the sample must be placed onto the filament before it is inserted into a heated chamber with carrier flow, placement of fibers and fine powders presents a problem. If these materials may not be melted onto the filament, they may fall off or blow off in the carrier gas stream before pyrolysis. Consequently, these sample types are generally analyzed using a small quartz tube, which is inserted into a coiled filament. The sample may be placed into the tube, held in position using plugs of quartz wool, weighed, and then inserted into the coiled element for pyrolysis. It... 

When a resistively heated filament pyrolyzer (e.g., the Pyroprobe from CDS Analytical, Inc., Oxford, PA) is used, the sample may be placed directly on a platinum filament or in a quartz tube or boat inside a platinum coil. In either case, the placement of sample with respect to the sampling tube or the ribbon should be the same for all samples. For liquid sample suspensions placed on a ribbon or in a coil, the solvent is evaporated prior to pyrolysis. Solid microbial samples can be sandwiched between quartz wool plugs inside the quartz sampling tube so as to reduce extraneous nonvolatile material from leaving the sampling tube during pyrolysis. With quartz, the sample never comes into direct contact with the pyrolyzer filament, as it does when sample is coated directly on a thin ribbon filament. Ribbon filaments sometimes exhibit a memory effect (particularly with polar components), are harder to clean, and typically have a shorter lifetime. Quartz tubes may be reused after cleaning. 

Stents can be divided into two main groups on the basis of the method of expansion. Balloon-expandable stents either arrive premounted on a balloon angioplasty catheter or are mounted by the doctor prior to the procedure. A balloon catheter with inflation apparatus is shown in Fig. 20.3. While mounted, the stent is moved into place and the balloon inflated to expand the stent to the desired diameter. Figure 20.4 illustrates the placement and inflation procedure for balloon-expandable stents. In contrast, self-expanding stents come premounted or sheathed. Once deployed to the treatment area, the sheath is pulled back, allowing the stent to expand to its predetermined diameter. Balloon-expandable stents can be further subdivided into slotted-tube and coil-based designs (Oes-terle et al., 1998). 

---