Page 496 - Practical Well Planning and Drilling Manual
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Appendix NEW! revised 11/00/bc  1/30/01  3:30 PM  Page 472








                     [          ]
                       Glossary



                       sticking require a permeable formation, a pressure overbalance across
                       a nearly impermeable filter cake and a stationary drill string.


                       Dipole Shear Sonic Imager tool. Schlumberger wireline tool that
                       records shear, compressional and Stoneley waveforms.  Used for
                       amplitude variation with offset (AVO) calibration, shear seismic cor-
                       relation, wellbore stability measurements, sanding analysis, fracture
                       height estimation, and sand mobility.


                       Dispersant. Any chemical which promotes dispersion of the dis-
                       persed phase.

                       Dispersed Phase. The scattered phase (solid, liquid, or gas) of a dis-
                       persion.  The particles are finely divided and completely surrounded
                       by the continuous phase.

                       Dispersion (Of Aggregates). Subdivision of aggregates.  Dispersion
                       increases the specific surface of the particle; hence results in an
                       increase in viscosity and gel strength.


                       Distillation. Process of first vaporizing a liquid and then condensing
                       the vapor into a liquid (the distillant), leaving behind non-volatile
                       substances, the total solids of a drilling fluid.  The distillant is the
                       water and/or oil content of a fluid.

                       Divalent. Having a valency of two.  When a salt is referred to as diva-
                       lent, the metal ion has a valency of two.

                       Dogleg. The “elbow” caused by a sharp change of direction in the
                       wellbore.

                       Dogleg Severity. A measure of how quickly the wellbore changes
                       direction, expressed in degrees (of total course change) per 100’ or
                       30m of wellbore length.


                       Dope. A generic term applied to all types of thread lubricants.  For
                       casing, tubing and line pipe use lubricants specified in API Bulletin
                       5A.  For tool joints and drill collars less than 7 inches OD, use a


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