Page 12 - A Primer of Oilwell Service and Workover Completion
P. 12
ANALYZING A WELL
Petroleum Extension-The University of Texas at Austin
ANALYZING A WELL
orking on an existing well REASONS FOR SERVICE
Wto restore or increase oil OR WORKOVER
and gas production is an impor-
tant part of today’s petroleum A well that needs service or
industry. Oil companies decide work over is not producing at all
whether to service or work over or is producing hydrocarbons at
a well based on two main fac- a rate not up to full potential.
tors: supplies of oil and gas, and Six general types of problems
their prices in the marketplace. may call for a service or work-
When oil prices are high, over con tractor: () excessive gas ORIGINAL GAS CAP
GAS-OIL
oil companies invest in drilling pro duction, () excessive water CONTACT EXPANDS
new wells because they expect produc tion, () poor production
rates, () production of sand,
to recover the costs quickly. In
through the early s, () equipment failure, or PERFORATIONS
for example, oil sold for about () depleted reservoirs.
$ a barrel, and an average LATER GAS-OIL CONTACT
of about , wells a month Excessive Gas Production
were being drilled in the United In wells with a gas-cap drive, the
States. In , the price had natural gas expands as liquids
dropped to about $ a barrel, flow out (fig. .). Originally,
and only about wells were perforations in the casing are Figure .. As oil is produced,
being drilled a month in the well below the gas cap, but even- the gas cap expands and reaches
United States. Fewer new wells tually the gas cap expands below the level of the perforations in the
casing or liner.
means the proportion of older the perforations. The well then
wells increases, and older wells starts producing a lot of gas with
need service or workover. the liquids. Exces sive gas pro-
duction depletes the gas, driving
the oil out of the reservoir.
