Page 12 - Air and gas Drilling Field Guide 3rd Edition

2 CHAPTER 1 Introduction and Units

technology. The use of this technology is limited to land drilling operations. There
are three subcategories of this technology: (1) air and gas fluids drilling, (2) aer-
ated fluids drilling, and (3) stable foam fluids drilling. This technology is utilized
by the industry to fulfill two specific drilling objectives.

Performance Drilling: This type of drilling takes advantage of the low annulus
bottom hole pressures that accompany the use of this technology. Low
annulus bottom hole pressures usually result in higher rates of penetrations.
This type of drilling operation is applied in the upper portions of a well bore
above the potential producing reservoir formation. The specific objective of
this type of drilling is to drill more rapidly through the upper formations above
the reservoir and to ultimately reduce the cost of a drilling operation.
Underbalanced Drilling: Here again, this type of drilling takes advantage of
the low annulus bottom hole pressure characteristic of the technology.
Underbalanced drilling uses the various bottom hole pressure capabilities of
air and gas, and aerated and stable foam drilling fluids to drill into potential
reservoir rock producing formations with annulus bottom hole pressures
lower than the static reservoir pressure. In this manner, the reservoir fluids
flow to the well bore as the drill bit is advanced through the reservoir.
Underbalanced drilling operations attempt to avoid damage to the reservoir
rock formation so that the reservoir will produce effectively through its life.

1.2 ENGINEERING CALCULATIONS AND UNITS
Modern engineering practices can be traced back to early eighth century AD
with the tradition of the “master builder.” This was the time of the creation of
the measure known as the Charlemagne foot. From the eighth century into the
seventeenth century a variety of weights and measures were used throughout
the world. It was not until the Weights and Measures Act of 1824 that a complete
British Imperial System (BIS) was codified within the British Isles, British Com-
monwealth countries, and in some of the former colonies of the British. The
United States actually did not accept the full BIS. The United States made use of
some of the major units within the system and some of the older units that had
evolved through the years of colonialism before 1824. This evolution of usage
within the United States ultimately became the United States Customary System
(USCS) (units that are still in common use today).
The development of some of the basic units that ultimately became part of the
present-day System International d’Unites probably began around the time of
Louis XIV of France. This system is simply known today as SI units (or metric
units). This system became codified by international treaty in France in 1875.
Most unit systems today, including the British Imperial System and the USCS,
are referenced to the actual existing weights (mass) and measures of the SI units.