Page 44 - Air and gas Drilling Field Guide 3rd Edition

CHAPTER

3
Surface Equipment

Air and gas drilling operations require some special surface equipment not nor-
mally used in rotary mud drilling operations. Shallow drilling operations usually
have this specialized equipment incorporated into the single rotary drilling rig
design. For the deeper drilling operations that use double and triple rotary dril-
ling rigs, this specialized surface equipment is usually provided by an air and gas
drilling equipment contractor. These contractors supply the rotary drilling con-
tractor (the drilling rig) with the necessary surface equipment to convert the
mud drilling rig to an air and gas drilling rig. The rotary drilling contractor
and the air and gas drilling contractor are usually contracted by an operating
company.

3.1 DRILLING LOCATION
Nearly all air and gas drilling operations are land operations. Figure 3-1 shows a
typical air drilling location plan for the drilling rig and the other important surface
equipment [1]. The plan in Figure 3-1 shows the location of the drilling rig (bore-
hole directly below the rotary table). This is a typical triple drilling rig configura-
tion. The drilling rig floor is larger and, therefore, it is easier to show the
important features of an air drilling operation with this type of rig. This rig is a
typical mud rotary drilling rig that has been set up to drill with compressed air
as the circulating fluid. The rig is powered by two prime movers on the rig
floor. These prime movers provide their power to the rig equipment through
the compound (a chain drive transmission system). The prime mover on a triple
rotary drilling rig like that shown in Figure 3-1 is limited to operating either
the rotary table or the draw works (hoist system), but not both simultaneously
[2]. The development of the hydraulic top head rotary drive, which replaces
the rotary table on most single and some double drilling rigs, allows the prime
mover to simultaneously operate the rotary action and the hoist system. These
smaller hydraulic top head rotary drive rigs use rig weight (via pull-down sys-
tems) to put axial force on the bit.
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