Page 514 - Practical Well Planning and Drilling Manual

Appendix NEW! revised 11/00/bc 1/30/01 3:30 PM Page 490

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Glossary

not be logged, although such other logs as the induction, acoustic
velocity, etc. can be run.

Nuclear Magnetism Log. Schlumberger wireline tool that applies a
large magnetic field to the formation, which causes the spin axis of
Hydrogen nuclei to align with the field. When the field is removed,
the relaxation of the free protons causes a signal in the measurement
coil. Used to estimate free porosity and produceability, estimate per-
meability, irreducible water saturation, residual oil saturation, and to
identify heavy oil zones. Cannot be run in combination with other
tools.

Nuclear Porosity Lithology Tool. Schlumberger wireline tool that
combines gamma density, neutron porosity, and natural gamma ray
spectrometry measurements in one tool. Used to deduce accurate
bulk density, neutron porosity, thin bed measurements, and density
measurements in formations with high natural radioactivity.

Oil Base Dipmeter Tool. Schlumberger wireline tool that uses four
microinduction sensors to measure the variations of formation con-
ductivity. Applications include determination of structural dip when
non-conductive mud is in use and borehole geometry.

Oil-Base Mud. The term “oil-base” is applied to a special type
drilling fluid where oil is the continuous phase and water the dis-
persed phase. Oil-base mud contains blown asphalt and usually 1 to 5
percent water emulsified into the system with caustic soda or quick
lime and an organic acid. Silicate, salt, and phospate may also be pre-
sent. Oil-base muds are differentiated from invert-emulsion muds by
the amounts of water used, method of controlling viscosity and
thixotropic properties, wallbuilding materials, and fluid loss.

Packer Fluid. Any fluid placed in the annulus between the tubing
and casing above a packer. Along with other functions, the hydrostat-
ic pressure of the packer fluid is utilized to reduce the pressure differ-
entials between the formation and the inside of the casing and across
the packer itself.

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