| ocs |
abbreviation: outer
continental shelf |
| off
production |
said of a well when it is shut in
or temporarily not able to produce. |
| offset well |
well drilled near another one. |
| offset-well
data |
information obtained from wells
that are drilled in an area close to where another well is being drilled or worked over.
Such information can be very helpful in determining how a particular well will
behave or react to certain treatments or techniques. |
| offshore |
that geographic area which lies
seaward of the coastline |
| offshore
drilling |
drilling for oil or gas in an
ocean, gulf, or sea, usually on the Outer Continental Shelf. A drilling unit for
offshore operations may be a mobile floating vessel with a ship or barge hull, a
semisubmersible or submersible base, a self-propelled or towed structure with jacking legs
(jackup drilling rig), or a permanent structure used as a production platform when
drilling is completed. In general, wildcat wells are drilled from mobile floating
vessels or from jackups, while development wells are drilled from platforms or jackups. |
| oil
and gas separator |
an item of production equipment
used to separate liquid components of the well stream from gaseous elements.
Separators are either vertical or horizontal and either cylindrical or spherical in
shape. Separation is accomplished principally by gravity, the heavier liquids
falling to the bottom and the gas rising to the top. A float valve or other
liquid-level control regulates the level of oil in the bottom of the separator. |
| oil-base
mud |
a drilling or workover fluid in
which oil is the continuous phase and which contains from less than 2 percent and up to 5
percent water. This water is spread out, or dispersed, in the oil as small droplets.
See oil mud. |
| oil
breakout |
oil that has risen to the surface
of the mud but which was previously combined with the mud as emulsion. |
| oil content |
the amount of oil in
volume-percent in a drilling fluid. |
| oil country tubular goods |
oil-well, casing, tubing, or drill
pipe. |
| oil-emulsion
mud |
a water-base mud in which water is
the continuous phase and oil is the dispersed phase. The oil is spread out, or dispersed,
in the water in small droplets, which are tightly emulsified so that they do not settle
out. Because of its lubricating abilities, an oil-emulsion mud increases the
drilling rate and ensures better hole conditions than other muds. Compare oil mud. |
| oil-emulsion
water |
the water contained in an emulsion
of oil and water. Also called milk
emulsion. |
| oilfield |
the surface area overlying an oil
reservoir or reservoirs. The term usually includes not only the surface area, but
also the reservoir, the wells, and the production equipment. |
| oil-in-water emulsion mud |
any conventional or special
water-base mud to which oil has been added. The oil becomes the dispersed phase and may be
emulsified into the mud either mechanically or chemically. Also called oil-emulsion mud. |
| oil mud |
a drilling mud, e.g., oil-base mud
and invertemulsion mud, in which oil is the continuous phase. It is useful in
drilling certain formation that may e difficult or costly to drill with water-base mud.
Compare oil emulsion mud. |
| oil
operator |
also called operator. See operator. |
| oil
- petroleum - gas |
a fluid of vapor composed of
hydrocarbons; dry gas is nearly free of oil and gasoline vapor. |
| oil pool |
the accumulation of oil in the
pores of sedimentary rock that yields petroleum on drilling. Not a pool or pond in
the ordinary use of the term. |
| oil sand |
any porous stratum bearing oil. |
| oil well |
a well completed for the
production of crude oil from at least one oil zone or reservoir. |
| oil zone |
a formation or horizon of a well
from which oil may be produced. The oil zone is usually immediately under the gas
zone and on top of the water zone if all three fluids are present and segregated. |
| old hand |
a man who has been around the oil
field for a long time. |
| one-trip |
a tool that goes downhole and is
not retrievable. |
| on-off tool |
a tool used to open or close a
downhole valve; a tool used to set or release a downhole tool, such as a retrievable
bridge plug. |
| on the horn |
someone talking on a two-way radio
to another person. |
| on the pump |
said of a well that is being
pumped. |
| on-vacuum |
said of any pressure-tight vessel
or container when the internal pressure is lower than atmospheric pressure |
| open |
1. of a wellbore, having no
casing. 2. of a hole, having no drill pipe or
tubing suspended in it. |
| open hole |
uncased portion of a well. |
| open-hole
completion |
a method of preparing a well for
production in which no production casing or liner is set opposite the producing formation.
Reservoir fluids flow unrestricted into the open wellbore. An open-hole
completion has limited use in rather special situations. Also called a barefoot completion. |
| opening/closing
plug |
a rubber plug used in primary
cementing operations to displace cement slurry from the casing into the borehole annulus. |
| opening
ratio |
the ratio between the pressure
required to open the preventer and the well pressure under the rams. |
| operator |
the person or company, either
proprietor or lessee, actually operating an oilwell or lease. Generally, the oil company
by whom the drilling contractor is engaged. |
| organic
theory |
an explanation of the origin of
petroleum, which holds that the hydrogen and the carbon that make up petroleum come from
plants and animals of land and sea. Furthermore, the theory holds that more of this
organic material comes from very tiny creatures of swamp and sea than comes from larger
creatures of land. |
| orifice |
an opening of a measured diameter
that is used for measuring the flow of fluid through a pipe, the orifice must be of
smaller diameter than the pipe diameter. It is drilled into an orifice plate held by
an orifice fitting. |
| O-ring |
a circular seal common in the
oilfield; requires deformation (squeeze) to energize and seal. |
| outer
continental shelf |
an offshore area in the United
States that begins where state ownership of mineral rights ends and ends where
international treaties dictate. |
| outrigger |
a projecting member run out at an
angle from the sides of a portable mast or a land crane to the ground to provide stability
and to minimize the possibility of having the mast or the crane overturn. |
| overproduced |
said of a well that has produced
more than its allowable. |
| out-running |
1. a condition in which fluid is
free-falling down the well at a faster rate than the pumps can handle. 2. in wireline, trying to pull out of the well faster than the
wireline tools are being blown upwards by unexpected pressure.
3. trying to pump out a gas influx before the expansion of
gas reduces pressure allowing the well to kick. |
| overbalance |
the extent to which the
hydrostatic pressure of the mud column exceeds formation pressure. |
| overburden |
the strata of rock that overlie
the stratum of interest in drilling. |
| overpull |
pull on pipe over and beyond its
weight in either air or fluid |
| overshot |
a fishing tool that is attached to
tubing or drill pipe and lowered over the outside wall of pipe or sucker rods lost or
stuck in the wellbore. A friction device in the overshot, usually either a basket or
as spiral grapple, firmly grips the pipe, allowing the fish to be pulled from the hole. |
