Tubing displacement

Nasogastric or orogastric Short-term Intact gag reflex Normal gastric emptying Manually at bedside Ease of placement Allows for all methods of administration Inexpensive Multiple commercially available tubes and sizes Potential tube displacement Potential increased aspiration risk... 

Tube displacement Self-extubation Vomiting or coughing Inadequate fixation (jejunostomy)... 

After cooling the tube, displace the chlorine with a stream of dry carbon dioxide. Transfer the preparation into a preliminarily weighed drawn out test tube (i.e. a tube with one end drawn out to a narrower diameter) and seal it wear eye protection ). Calculate the yield in per cent. What is the colour and composition of the prepared substance ... 

Nasogastric or orogastric Short-term Manually at bedside Ease of placement Potential tube displacement... 

High risk of GER or aspiration Endoscopically Multiple commercially available tubes and sizes Potential tube displacement or dogging... 

A = horizontal tube displacement flow reactor = rotary vertical batch type reactor... 

Figure 9.4 AFM force curve from Au(l ll)-BMIPF interface, showing clear stepwise force changes at —0.8 V versus Pt quasi-reference electrode. The horizontal axis is the relative reading of Z-piezo tube displacement.

Figure 10.13 Sample recovery. (A) The bottom of a celluloid centrifuge tube is pierced with a hypodermic needle. The fractions drip into a series of tubes. (B) CcAlection of samples separated on a discontinuous gradient by displacement technique. The three layers of gradient have been assigned arbitrary density values. A higher density solution when pumped into the tube displaces the gradient which is collected into fractions.

This is a periodic treatment in which a large quantity of chemicals is used for an extended period of time. It is commonly used to treat flowing oil wells. Batch treatment is also called slug treatment For batch treating, the tube displacement method is employed. Several barrels of inhibitor are pumped into the tubing at the top. The inhibitor is displaced to the bottom of the tubing with the fluids in the oil well. The well is closed for a specific period before operation. The batch is used mciinly to treat water with biocides and not to supply inhibitors or scavengers. 

Sometimes a short batch is forced down with a nitrogen displacement or compressed gas to speed up the fall rate and reduce shut-in time. An inhibitor squeeze is sometimes used to try to get a longer return time and simulate a continuous treatment. However, there is always the concern of formation damage with squeezes and with tubing displacements. 

Using the techniques described above immediate problems of inadvertent perforation of other structures, loss of access with entry into the peritoneal cavity and haemorrhage are rare. Longer term problems include tube displacement, tube blockage and buried bumper. 

Tubing displacements are handled the same as squeezes except there is no over-displacement. One drum of the inhibitor mixed in the displacement fluid is added and the well is left shut in for about three hours after displacement is accomplished. The total volume of fluid-spearhead plus displacement should be only sufficient to displace to the bottom of the tubing. If the fluid level tends to drop, or the well goes on vacuum, the liquid will collect in the hold beneath the tubing instead of being sucked into the formation. 

Inhibitors for batch treatment or tubing displacement in gas wells are returned to the surface cut with water and distillate. The inhibitor concentration is high, and at high concentrations some inhibitors behave as good emulsifiers for water and oil. For this reason the inhibitors reconunended for gas wells contain emulsion breakers to prevent emulsions that cause trouble in separators. 

If a well is a flowing oil well making mostly fluid (oil and water), the shut in conditions will leave considerable fluid in the tubing. This well is best treated by a tubing displacement or squeeze if the bottom pressure is sufficient to return the injected fluids. This type of well can also be treated with weighted inhibitors. 

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