r - part - usaid

cost of running them, Without additional facilities, a drill
rig has a storage capacity of 756 liters of fuel. At an assumed
rate of consumptian of 300 liters per day while drill.ing (50
likers per hour fur 6 hours), this lasts snfy two and a half
days. In the Bay Region, where distances are nut sa great and
where road conditions are generally better, one fuel truck can
service three rigs, In the Central Range, one fuel truck is
req~ired
for each rig.
The same rationale appzies to the fact that while one water
truck is required for each rig in the Bay Region, two are needed
for each rig in the Central Range, One of these two is based at
the site and used as a stationary starage facility, necessary
because the distance to the nearest water supply may be as far
as seventy-Eivs kilometers.
The equivalent of cne heavy truck is required for each rig
operating in the Bay Region. This represents one knuckle-crane
truck and one flat-bed truck, each shared between two rigs, In
the Central Range the knuckle-crane truck is required to be on
site far the whole time. In most circumstances in the Central
Ra1':ge n flat-bed truck, which is only used to deliver ampplies,
could still be shared between two rigs,
As demonstrated in the BranAon analysis, one obviaus
conclusian fron the above data is that the rate of drilling is
of paramount iaportance. The Groundwater Project has achieved
an overall averzge of 36 working days at each rotary rig
borehole [ap~zaximately 100 borehales in 4 years by 3 rigs).
Not infrequently, however, the drilling crews have completed
their task at the site and moved on within 10 days- The
vzriance about this mean is obviously high. It is not at a11
unusual far WDB drilling crews noh u~>rking an the project to
spend six months or even a f-ll year at one site. In some
cases, this may be the rsault of the slow rate of drilling of
the older cable t asP rigs; it can more often be attributed to
mechanical breakdown or lack of supplies, particularly fuel.
In very simple terms, a rig costing $400,000, with an
expected life of 10 years, drilling 8 boreholes each year,
shouzd charge $5,000 far each borehole for capital recovery
costs. The same rig drilling one borehoie every six months w ill
need to charge $20,000 for each borehole. The answer to this
difficult costing question lies not in desig~ing a costing
system to deal with it, but in maintaining z high drilling rate,
Economies on equipm~gt maintenance and supplies of fuel are, fn
fact, false ecsnoaies.
In a separate calculation, reproduced in Table 2.4.7, the
cost of an idle drilling team operating a production drilling
program in the Bay Region has been calculat-ed at $365 per day.