The ratio of the electron density to the bulk density. The electron density is equal to the bulk density multiplied by 2Z/A where Z is the average atomic number and A is the average atomic weight of the formation. The density log actually responds to electron density, whereas the desired measurement is the bulk density. Although for most rocks 2Z/A is close to 1, it is not practical to adjust 2Z/A for each formation. Instead the electron density is scaled to give the correct bulk density in limestone filled with fresh water. Then it is found that in the majority of sedimentary rocks, the log reads the bulk density within 1%. The main exceptions are halite, sylvite and low-pressure gas, because the 2Z/A of chlorine and hydrogen are not close to 1.
Zero offset vertical seismic profile
A conventional vertical seismic profile in which the energy source is positioned directly above the receivers, typically very close to the wellbore
Zinc basic carbonate
A neutral double salt of zinc carbonate and zinc hydroxide in 2-to-3 stoichiometric proportions, 2ZnCO3·3Zn(OH)2. Zinc basic carbonate is used as a sulfide scavenger for water-base drilling fluid in a concentration of about 0.1 lbm/bbl per 50 mg/L GGT sulfides (determined by Garrett Gas Train sulfide analysis of the filtrate). The zinc cation reacts with the sulfide anion to form inert zinc sulfide (ZnS).
A reduced-diameter section that has been machined at the box (up) end of a drill collar (usually a straight drill collar) so that the collar may be more easily handled with open-and-close elevators. The elevators close around the reduced-diameter section, latch securely, and a shoulder on the elevators prevents the larger diameter end of the collar from passing through the elevators, so the collars can be lifted. If zip grooves are not used on the collars, special lifting subs must be threaded into each stand of collars for lifting, which is time-consuming and less efficient than zip grooves. The primary drawback to zip grooves is that they may reduce the life of the collar by putting an effective limit on how many times the collar threads may be recut.