Gas separation: apparatus – Degasifying means for liquid – Defoaming means
Reexamination Certificate
1999-05-11
2001-02-13
Smith, Duane S. (Department: 1724)
Gas separation: apparatus
Degasifying means for liquid
Defoaming means
C095S253000, C095S262000, C096S182000, C096S184000, C096S188000, C096S198000, C096S219000, C096S220000
Reexamination Certificate
active
06187079
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a phase separator. More particularly, this invention relates to a motion-insensitive phase separator for use in marine applications.
Phase separators are used in the oil industry to separate oil and gas from water in a multi-phase production fluid from a well bore. Most oil deposits occur in combination with water and gas. Frequently, because of the high geologic pressures involved, the oil is more or less homogeneously mixed in with the water, and the gas is dissolved in the mixture. Phase separators serve to separate out the three phases so that the oil and gas can be further processed.
Where drilling for oil and gas is undertaken over an ocean or other body of water, the phase separators are frequently located on a vessel maintained in position at sea. One problem arising in these installations is that the motion of the vessel and consequently of the phase separator causes the incoming fluid mixture to slosh about within the separator, thereby generating foam and impeding the separation process.
Separators which are used at sea are generally provided with structure for combating the effects of wave induced motion. As illustrated in
FIG. 1
, one such prior art phase separator includes a tank
12
having a single, centrally located, inlet
14
. A packed box distributor
16
is disposed at the inlet
14
for spreading out the incoming fluid mixture throughout the tank
12
. Tank
12
is provided with a pair of spaced gas outlets
18
and
20
, a centrally located water outlet
22
and a centrally located oil outlet
24
. A liquid containing chamber
26
is defined inside tank
12
by a separator plate
28
and a pair of partitions
30
and
32
in which respective flapper valves
34
and
36
are located. Water outlet
22
and oil outlet
24
communicate with chamber
26
. Water outlet
22
is located at a bottom of tank
12
, below a water level or water-oil interface
38
, while oil outlet
24
is located between water level
38
and an oil level or oil-gas interface
40
. Also located inside chamber
26
are separation media in the form of a plurality of packing structures
42
which serve to separate the oil and the water components from one another.
FIG. 2
depicts another separator designed specifically for marine applications. An elongate tank
44
is provided at one end with an inlet
46
for delivering a fluid mixture to tank
44
. At an opposite end of tank
44
are provided a gas outlet
48
, a water outlet
50
and an oil outlet
52
. A cyclonic preseparator inlet device
54
is located at inlet
46
, while a plurality of packing structures or perforated plates
56
are disposed at the bottom of tank
44
between inlet
46
and outlets
48
,
50
, and
52
. Water outlet
50
is located at a bottom of tank
44
, below a water level or water-oil interface
58
, while oil outlet
52
is located between water level
58
and an oil level or oil-gas interface
60
.
SUMMARY OF THE INVENTION
A motion-insensitive phase separator for separating oilfield production fluid phases comprises, in accordance with the present invention, a tank having a pair of opposing inlets and generally centrally arranged outlets for liquid phases of a production fluid mixture fed into the tank simultaneously through the inlets. Separation media are disposed in the tank for separating the different phases of the production fluid. The separation media extend across a fluid flow path which in turn extends from the inlets to the outlets. Preferably, the inlets are disposed substantially equidistantly from the outlets, while the fluid permeable phase separation media is disposed in said tank generally symmetrically about the outlets. This structure provides for a symmetrical flow and weight distribution for motion insensitivity.
Generally, it is contemplated that there are at least three outlets for oil, water and gas, respectively. In this case, the separator is a three-phase separator. The liquid outlets are preferably arranged in a vertical median plane of the tank. Depending on the physical constraints of the particular application, however, a perfect central disposition of the liquid outlets may not be possible.
Where the tank is an elongate cylindrical tank having opposed end walls, the inlets are each disposed at a respective one of the end walls.
A tank in accordance with the present invention is generally mounted to an upper deck of a tanker or other ocean-going vessel. The tank has a longitudinal axis which is disposed in parallel to the longitudinal axis of the vessel. Since the pitching motion of a vessel is generally less than the rolling motion thereof, this disposition of the tank relative to the carrier vessel minimizes the motion which gives rise to sloshing of the liquids in the tank.
Preferably, the separation media include antifoam media at opposite ends of the tank and further include demisting media proximately to the median plane, on opposite sides thereof. The demisting media define a centrally located, chamber in which the liquid outlets are located.
In accordance with another feature of the present invention, the separator further comprises flow restrictors or regulators in the form of perforated plates disposed in the tank between the antifoam media and the demisting media. The perforated plates restrict, limit or regulate the flow of liquid along a fluid path from the inlets at the ends of the tank towards the water and oil outlets at or near the center of the tank, so as to prevent precipitous rushes of liquid induced by the heaving, pitching and rolling of a vessel on which the separator is located.
Preferably, the perforated plates extend up through a separated liquid region in the tank to a point located above an uppermost liquid level. This prevents liquid from washing over the perforated plates even in high seas.
Like the separation media, the perforated plates are located at least approximately symmetrically about a central transverse plane of the tank, thereby enhancing or assisting in the generation of a symmetrical flow and weight distribution for motion insensitivity.
It is contemplated that the antifoam media, the demisting media and the additional media also extend up through a separated liquid region in the tank to a point located above an uppermost liquid level. Preferably, at least the demisting media extend transversely across the tank from the bottom to the top thereof.
In a three-phase separator in accordance with the present invention, simultaneous infeed from opposite ends of the tank offers reduced size and weight as compared to other designs, for example, those in which a central separator plate and flapper valves are provided. The separation media and perforated plates minimize the effects of vessel motion. Moreover, the separator can be smaller for a given volumetric flow rate than conventional designs.
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patent:
Baker Hughes Incorporated
Coleman Henry D.
Smith Duane S.
Sudol R. Neil
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