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CHAPTER FIVE

Equipment in Gas Drilling
Systems

Contents
5.1 Introduction 109
5.2 Surface Equipment 109
5.3 Downhole Equipment 114
Summary 117

5.1 INTRODUCTION

The gases used in gas drilling can be air, natural gas, or nitrogen.
Gas injection systems are similar when different types of gases are used.
Figure 5.1 shows a typical gas drilling system that uses air (Lyons et al.,
2009). The air travels (1) from the atmosphere to the compressor,
(2) from the compressor through the standpipe and the kelly pipe to the
drill string that consists of drill pipes and drill collars, (3) through the drill
string to the bit, (4) through the bit and up the annular space between
the drill string and the borehole (open hole and cased hole sections) to
the surface, and (5) through the rotating head to the blooey line and
back to the atmosphere. This chapter provides a brief introduction to the
equipment that controls gas injection pressure.

5.2 SURFACE EQUIPMENT
Figures 5.2, 5.3, and 5.4 show layouts of the surface equipment in
air drilling systems, natural gas drilling systems, and nitrogen drilling sys-
tems, respectively. In all of these systems, the most important equipment
includes the compressors and the boosters (high-pressure, high-volume
compressors). Different types of gas compressors are used in the oil and
gas industry. These designs vary greatly in volume and pressure ratings.
Gas compressors are very similar to liquid pumps in their basic design and
operation. The basic difference is that compressors move compressible
fluids, whereas pumps move incompressible fluids.

Applied Drilling Circulation Systems. DOI: 10.1016/B978-0-12-381957-4.00005-X
© 2011 Elsevier Inc. All rights reserved. 109