Perforating fluid

Perforating fluids used may be filtered clear brine or CaCO, type completion fluids, oil, seawater, acetic acid, gas or mud. 

Packer fluids are used to provide hydrostatic balance to partially offset the reservoir pressure and eliminate a large pressure differential across the packer element. TKPP solutions more than meet the requirements of being noncorrosive, nondestructive to elastomers, variable in density, and stable for many years. It is desirable to perforate with a well bore filled with packer fluid so that the packer can be set and the well produced as soon as the perforation operation is complete. Since TKPP solutions make superior perforation fluids, their dual use as a packer fluid is further enhanced. 

A. Iron has a direct corrosive effect on mucosal tissue and may cause hemorrhagic necrosis and perforation. Fluid loss from the gastrointestinal tract results in severe hypovolemia. 

Completion and perforation history must then be evaluated. Completion practices—and the fluids used therein—are potentially damaging. For example, perforating in dirty fluids can be very damaging. Unfiltered solids in perforating fluid are injected at such high velocity during the perforation process that plugging can be extremely severe. 

In carbonate formations, acetic add (usually 9% or 10%) is an effective perforating fluid. It may also be weighted up by inclusion of salt, if required. Acetic is a mild add but strong enough to dissolve perforation debris, resulting in clean perforations. If necessary following well completion, perforations may be cleaned or stimulated further with a small acid treatment, typically acetic acid (10%-15%) or HCl (7.5%-15%). 

Acetic acid. Acetic add is a weakly ionized, slow-reacting organic acid. Acetic acid is easier to inhibit against corrosion than HCl. For this reason, acetic acid has application as a perforating fluid in carbonate wells and as a stimulation fluid in high-temperature formations. 

Sometimes primary cementations are not successful, for instance if the cement volume has been wrongly calculated, if cement is lost into the formation or if the cement has been contaminated with drilling fluids. In this case a remedial or secondary cementation is required. This may necessitate the perforation of the casing a given depth and the pumping of cement through the perforations. 

Permeability (k) is a rock property, while viscosity (fi) is a fluid property. A typical oil viscosity is 0.5 cP, while a typical gas viscosity is 0.01 cP, water being around 0.3 cP. For a given reservoir, gas is therefore around two orders of magnitude more mobile than oil or water. In a gas reservoir underlain by an aquifer, the gas is highly mobile compared to the water and flows readily to the producers, provided that the permeability in the reservoir is continuous. For this reason, production of gas with zero water cut is common, at least in the early stages of development when the perforations are distant from the gas-water contact. 

To reduce this tendency the well should be produced at low rate, and the perforations should be as far away from the OWC as possible. Once the unwanted fluid breaks through to a well, the well may be recompleted by changing the position of the perforations during a workover, or the production rate may be reduced. 

The purpose of the well completion is to provide a safe conduit for fluid flow from the reservoir to the flowline. The perforations in the casing are typically achieved by running a perforating gun into the well on electrical wireline. The gun is loaded with a charge which, when detonated, fires a high velocity jet through the casing and on into the formation for a distance of around 15-30 cm. In this way communication between the wellbore and the reservoir is established. Wells are commonly perforated after the completion has been installed and pressure tested. 

Fig. 13. Multistage spout-fluid-bed reactor. 1, spouted bed 2, perforated plate 3, spray no22le 4, air header 5, fluidi2ed bed.

The basic fluid-bed unit consists of a refractory-lined vessel, a perforated plate that supports a bed of granular material and distributes air, a section above the fluid bed referred to as freeboard, an air blower to move air through the unit, a cyclone to remove all but the smallest particulates and return them to the fluid bed, an air preheater for thermal economy, an auxiUary heater for start-up, and a system to move and distribute the feed in the bed. Air is distributed across the cross section of the bed by a distributor to fluidize the granular soflds. Over a proper range of airflow velocities, usually 0.8-3.0 m/s, the sohds become suspended in the air and move freely through the bed. 

Instant Active Dry Yeast. Instant ADY (lADY or HADY) production is similar to ADY production but requires a different strain of yeast. After pressing, the yeast is extmded into noodles 0.2—0.5 mm in diameter and 1—2 cm long and deposited on a metal screen or perforated plate in a fluid-bed air dryer. Drying time is shorter than with ADY, about 1—2 hours in practice, with a final moisture level of 4—6%. Instant active dry yeast does not require separate rehydration. It is always packaged in a protective atmosphere or under vacuum. On an equivalent soHds basis, the activity of lADY is greater than that of regular ADY, but stiU less than that of compressed yeast. 

Figure 4.20 Sulfide deposits (dark patches) on longitudinally split brass heat exchanger tube. Note the perforation where wastsige penetrated the tube wall. Sulfide was spalled after perforation by escaping fluids.

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