STANDARD HANDBOOK OF PETROLEUM & NATURAL GAS ...

840 Drilling and Well Completions
Example
A tricone roller rock bit is furnished with three nozzles with the diameters
of -&, +!j and $j in. Calculate the bit pressure drop if the mud weight is 10 Ib/gal
and flowrate is 300 gpm.
Nozzle equivalent diameter is
d,, = 1-
= 0.5643 in.
and the corresponding flow area is
The pressure loss through bit nozzles is
AIR AND GAS DRILLING
Types of Operations
Air and natural gas have been used as drilling fluids to drill oil and gas wells
since 1953. There are basically four distinct types of drilling using these fluids:
air and gas drilling with no additives (often called dusting), unstable foam
drilling (also called misting), stable foam drilling and aerated mud drilling [64].
Air and natural gas have also been used as drilling fluids in slim-hole-drilling
mining operations, special large-diameter boreholes for nuclear weapons tests,
and, more recently, in geothermal drilling operations.
Air and natural gas drilling techniques are used principally because of their
ability to drill in loss-of-circulation areas where mud drilling operations are
difficult or impossible. These drilling fluids have other specific advantages over
mud drilling fluids when applied to oil and gas well drilling operations, which
will be discussed later in this section. In general, air and gas drilling techniques
are restricted to mature sedimentary basins where the rock formations are well
cemented and exhibit little plastic flow characteristics. Also, to varying degrees,
air and gas drilling techniques are restricted to drilling in rock formations that
have limited formation water or other fluids present.
In the United States, air and gas drilling techniques are used extensively in
parts of the southwest in and around the San Juan Basin, in parts of the Permian
Basin, in Arkansas and eastern Oklahoma, in Maryland, Virginia and parts of
Tennessee. Internationally, oil and gas drilling operations are carried out with
air and gas drilling techniques in parts of the Middle East, North Africa and
in the Western Pacific.