Page 502 - Practical Well Planning and Drilling Manual

Appendix NEW! revised 11/00/bc 1/30/01 3:30 PM Page 478

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Glossary

hole wall. Can show fractures, bedding planes, and differentiate
between different lithologies.

Formation MicroScanner tool. Schlumberger wireline tool that pro-
vides continuous, oriented borehole images. Applications include
structural analysis, fracture identification and analysis, sedimentary
analysis, high resolution reservoir analysis, and depth matching / ori-
entation of cores.

Fracture gradient. The gradient from surface showing at what pres-
sure a formation will fracture. Usually measured during leak off tests,
can be expressed in the same terms as mudweight - PSI/Ft, PPG, etc.

Free Point Indicator Tool. Schlumberger wireline tool run inside
drillpipe when stuck. When on depth, anchors are deployed and the
drillstring worked in tension and torsion. Tool allows an estimate of
stuck depth prior to attempting an explosive backoff.

Functions of Drilling Fluids. The most important function of
drilling fluids in rotary drilling is to bring cuttings from the bottom
of the hole to the surface. Some other important functions are: con-
trol subsurface pressures, cool and lubricate the bit and drill string,
deposition of an impermeable wall cake, etc.

Galena. Lead Sulphate (PbS). Technical grades (specific gravity
about 7) are used for increasing density of drilling fluids to points
impractical or impossible with barite.

Gamma Ray Spectrometry Tool. Schlumberger wireline tool that
emits high energy neutrons into the formation, activating the atomic
elements. Used for reservoir evaluation through casing and water-
flood monitoring.

Gas Cut. Gas entrained by a drilling fluid.

Gas-Oil Ratio. A measure of the volume of gas produced with the
oil. It is expressed in cubic feet per barrel.

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