Mechanical placement

Mechanical placement of acid was the first means thought of for improving contact with the interval to be treated. Currently, the following general acid placement methods exist  

They are not necessarily stand-alone methods, as coiled-tubing injection and ball sealers can be combined with isolation packer systems. 

Packer systems. Mechanical placement is the most certain method of acid diversion. Mechanical placement, or diversion, includes the use of inflatable straddle packer systems, bridge plug/packer combinations, and special wash tool packer systems, to physically isolate short sections of long treatment zones. 

There are a number of commercial packers and packer system manufacturers. Improvements in such treatment tool sj tems and extensions of their application are continually made. Information on packer systems and their uses, including design for specific applications, can be obtained from the major packer manufacturers or pumping service companies. 

Isolation packers for use in acid stimulation are effective in a well completion only if acid will enter perforations and continue flowing into the formation. If a poor cement job is present, acid may channel vertically along the cement/formation interface, defeating the purpose of mechanical placement. Of course, mechanical placement of add with packer systems is valid only in perforated, cemented pipe completions. As of this writing, reliable mechanical placement techniques for small-diameter, monobore (slimhole) completions do not exist. 

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Palletizers are available in high-level, low-level, or robotic versions. In high-level palletizers, the case or product enters the palletizer via an overhead conveyor. In a low-level system, the case or product enters the palletizer at floor level or approximately 75-90 cm off the floor. Robotic palletizers generally operate at floor level and involve mechanical placement of the cases and/or rolls. 

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. 

As mentioned already, there have been and still remain two basic methods for placing add mechanical placement and chemical diversion. Mechanical placement alone is a method that allows acid to contact most of the zone of... 

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. 

Another limitation to mechanical placement is cost. Packer systems often require a rig. Moreover, specialty packers may themselves be expensive. Nevertheless, mechanical placement with packers is the most reliable option and the best method for improving treatment zone coverage during add stimulation. 

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