Page 524 - Practical Well Planning and Drilling Manual

Appendix NEW! revised 11/00/bc 1/30/01 3:30 PM Page 500

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Glossary

Turbulent Flow. Fluid flow in which the velocity at a given point
changes constantly in magnitude and the direction of flow; pursues
erratic and continually varying courses. Turbulent flow is the second
and final stage of flow in a Newtonian fluid; it is the third and final
stage in a Bingham plastic fluid.

Twist-Off. To twist a joint of drill pipe in two by excessive force
applied by the rotary table. Many failures which result in parting of
the drill pipe in the well bore are erroneously referred to by this term.

Ultrasonic Imager. Schlumberger wireline tool that uses a single
rotating ultrasonic sensor to provide a complete image of the casing,
cement, and annulus. Can show casing damage/corrosion, cement
quality, and channeling.

Under-Ream. To enlarge a drill hole below the casing.

Valency. This expresses the number of electrons that an atom or
group of atoms needs to lose, gain or share to attain electrical stabili-
ty. See also Covalent and Ionic.

Variable bore rams. Pipe rams that can close over a range of pipe
sizes. VBRs cannot be used to hang off the drillstring.

Velocity, Critical. That velocity at the transitional point between
laminar and turbulent types of fluid flow.

Velocity. Time rate of motion in a given direction and sense. It is a
measure of the fluid flow and may be expressed in terms of linear
velocity, mass velocity, volumetric velocity, etc. Velocity is one of the
factors which contribute to the carrying capacity of a drilling fluid.

Vertical seismic profile. Uses downhole sonic tools that are processed
to provide a map of the acoustic response of the earth along the well-
bore. Useful for prediction ahead of the bit, dip evaluation, thin bed
analysis, seismic evaluation of deep horizons, timing and amplitudes
of multiples, and direct wave attenuation with depth. Measurements
can be made with a single surface source (zero offset VSP) or with a
moving surface source (walkaway VSP), and the waves recorded

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