CA2857249A1 - Oilfield production tank with divided interior and top-to-bottom fluid transfer passage between divided spaces - Google Patents

Abstract

An oilfield production tank has its interior divided into first and second spaces. A fluid passage has an inlet positioned within the first space of the tank interior on a first side of the divider at a first height nearer an upper end of the divider than a lower end of the divider. An outlet of the fluid passage opens into the second space of the tank interior on a second side of the divider at a second height that is lower than the first height. Oil from a production well enters the tank on the first side of the divider. Relatively clean oil separates to the top of the first space, and then travels via the passage to a lower elevation in the second space, where a second separation stage occurs to allow drainage of cleaner oil from the top of the second space.

Description

OILFIELD PRODUCTION TANK WITH DIVIDED INTERIOR AND TOP-TO-BOTTOM FLUID TRANSFER PASSAGE BETWEEN DIVIDED SPACES
FIELD OF THE INVENTION
The present invention relates generally to production storage tanks used in the oilfield to store hydrocarbon-containing fluids produced from a well, and more particularly to such a tank in which the interior is divided into separate spaces that respectively fed and drained by the tank inlet and outlet.
BACKGROUND OF THE INVENTION
It is known in the prior art to provide an oilfield production tank whose interior is divided into two separate volumes by an internal vertical baffle, as disclosed in Canadian Patent Application No. 2,665,578 entitled Dual Production Tank. The tank features a fire tube in each of the space to aid in separation of the oil, water and sand of the incoming production fluid.
However, there remains room for improvement, and Applicant has developed a unique divided production tank not heretofore seen.
Other prior art relevant to processing of the raw well fluids to separate out the components same can be found in CA2108297, US5042582 and US5928519, but these involve initial separation of gases and liquids prior to storage, and thus involve use of high pressure vessels unlike the minimal or zero-pressure production storage tanks with which the present invention is concerned.
U.S. Patent No. 3,340,477 discloses a separation tank for water-oil separation of produced emulsions of a hydrocarbon liquid and aqueous solution, but employs a structure notably different than the production tank of the present invention.
SUMMARY OF THE INVENTION
According to one aspect of the invention there is provided an oilfield production tank comprising:
a tank enclosing an interior;
a divider arrangement mounted at a location within the tank and dividing a first space of the interior from a second space of the interior over a majority of a height of the tank at the location of the divider;
a fluid passage having a fluid passage inlet positioned within the first space of the interior of the tank on a first side of the divider at a first height nearer an upper end of the divider than a lower end of the divider, and a fluid passage outlet that opens into the second space of the interior of the tank on a second side of the divider at a second height that is lower than the first height;
a tank inlet opening into the interior of the tank on the first side of the divider for ingress of produced well fluid into the tank through said tank inlet;
a tank outlet opening into the interior of the tank on the second side of the divider for egress of fluid from the tank through said tank outlet.
Preferably the divider arrangement comprises an upright baffle.
The fluid transfer passage may be defined by a downcomer that is engaged with an opening in the baffle to deliver fluid from the first space to the second space through the upright baffle at said opening therein.
The downcomer may extend through the opening.

In one embodiment, the downcomer engages with the opening in the baffle at a height closer to the fluid passage inlet than to the fluid passage outlet, and runs downwardly from said height on the second side of the upright baffle.
There may be provided a control mechanism operable to adjust the first height at which the fluid passage inlet is located in order to control a fluid level to which the first space will fill before reaching the fluid passage inlet.
In one embodiment, the control mechanism comprises:
a sleeve slidably disposed over an upright length of pipe that forms a portion of the fluid passage; and at least one inlet opening that opens into an interior of said sleeve at an area of the sleeve that is movable within a range of heights disposed above the top end of the upright length of pipe.
The control mechanism may further comprise an actuator operable to raise and lower the sleeve to adjust a position of the inlet opening of the sleeve relative to the top end of the upright length of pipe.
The actutator of the control mechanism may comprise a control linkage having an input end and an opposing output end coupled to the sleeve for sliding movement thereof along the length of upright pipe under movement of the input end of the control linkage.
The actutator of the control mechanism may comprise a control lever having an input end, an opposing output end and a pivot point between the input and output ends, the output end being coupled to the sleeve by an intermediate link for sliding movement thereof along the length of upright pipe under pivotal movement of the input lever about the pivot point.
The input end of the control linkage may be positioned externally of the tank for manual manipulation of the input end from outside the tank.
In another embodiment, the control mechanism may comprise a tubular elbow having a first end thereof that is coupled by a swivel joint to an inlet end of a lateral length of pipe that forms part of the fluid passage to enable pivoting of the tubular elbow about an axis of the swivel joint to adjust a height of an opposing second end of the tubular elbow relative to the inlet end of the lateral length of pipe.
The lateral length of pipe may extend through the divider arrangement from the first side thereof to the second side thereof, at which the lateral length of pipe is joined to an upright section of pipe running downwardly along the divider arrangement toward the fluid passage outlet.
The control mechanism may comprise an actuator comprising an elongated flexible lift member having an output end thereof coupled to the tubular elbow from above for raising of the second end of the tubular elbow under pulling of the elongated flexible lift member.
The elongated flexible lift member may be routed to an exterior of the tank for operation of the control mechanism from outside the tank by manually driven pulling of the elongated flexible lift member.
Preferably the control mechanism comprises a locking device operable to lock a position of the fluid passage inlet at a selected height.

Preferably there is a fluid pathway between the first and second spaces at an elevation spaced above the inlet of the fluid transfer passage.
The upper end of the divider arrangement is preferably spaced below an upper end of the interior of the tank to leave an open space defining the fluid 5 pathway between the upper end of the divider arrangement and the upper end of the interior of the tank.
Preferably the divider arrangement reaches fully to a bottom of the interior of the tank in order to separate the first and second spaces entirely from one another over an area spanning from the bottom of the interior of the tank to the upper end of the divider arrangement.
Preferably the tank inlet is disposed at a lower elevation than the fluid passage inlet.
BRIEF DESCRIPTION OF THE DRAWINGS
In the accompanying drawings, which illustrate exemplary embodiments of the present invention:
Figure 1 is a side elevational view schematically showing an oilfield production tank of a first embodiment of the present invention in cross-section.
Figure 2 is an elevational view schematically showing an oilfield production tank of a second embodiment of the present invention in cross-section.
Figure 3 is an elevational view schematically showing an oilfield tank of a third embodiment of the present invention in cross-section.

Figure 4 is a partial elevational view showing a variant of the first embodiment tank which features a first type of control mechanism for controlling transfer of fluid from one divided space of the tank interior to another.
Figure 5 is a partial elelvational view showing a variant of the third embodiment tank which features a second type of control mechanism for controlling the transfer of fluid between the divided spaces of the tank interior.
DETAILED DESCRIPTION
Figure 1 schematically shows an oilfield production tank 10 according to a first embodiment of the present invention. The tank may have the same cylindrical outer shape as conventional production tanks, where a cylindrical outer wall 12 circumscribes a cylindrical interior volume of the tank at barometric pressure.
A top wall 14 overlies the cylindrical interior volume of the tank, and may have a peaked or domed configuration delimiting a headspace overtop of the cylindrical volume bound by the circumferential outer wall 12.
A vertical baffle 16 stands upright from a floor 17 that lies opposite the top wall 14 and defines the bottom of the tank's interior volume. The illustrated baffle 16 stops short of the top wall 14 of the tank, leaving an open space between an upper end 16a of the baffle 16 and the top wall. An L-shaped pipe or assembly of pipes defines a downcomer 18 having a first vertical leg 18a that depends downwardly along the baffle 16 on a first side thereof at a distance outward therefrom, and a second horizontal leg 18b that is integrally or otherwise attached to the lower end of the first leg to turn at an angle therefrom in a lateral direction passing through the baffle 16. The open end 20 of the first leg 18a of the downcomer 18 defines an inlet of the downcomer on the first side of the baffle, and the open end 22 of the second leg 18b of the downcomer forms an outlet thereof on the second side of the baffle.
Over the height of the interior volume that is spanned by the baffle, the interior volume is divided into two separated spaces on the respective sides of the baffle. The downcomer thus fluidly communicates with the first space on the first side of the baffle only at the downcomer inlet 20 near the top end 16a of the baffle, and fluidly communicates with the second space of the second side of the baffle at the downcomer outlet 22 near where the lower end of the baffle 16 is attached to the floor 17 of the tank interior.
A tank inlet 24 opens into the tank interior on the first side of the baffle through the circumferential wall 12 at a height thereon near, but spaced above, the tank floor 17 at an elevation thus located well below the downcomer inlet 20.
A tank outlet 26 similarly opens into the interior space, but on the second side of the baffle 16. Accordingly, the tank inlet 24 feeds into the first space of the tank interior, while the tank outlet 26 instead communicates with the second space of the tank interior.
Produced well fluids are conveyed into the tank interior, specifically into the first of the two divided spaces thereof, through the tank inlet 24 via an input line coupled thereto (not shown). This incoming production fluid may contain oil, water, gas and sand. As is well known in the art, these materials will tend to separate from one another once fed into the tank, with the sand sinking to the tank floor and the water tending to separate from the oil. Due to differences in density, the oil will tend to rise through the water, resulting an upper layer of oil disposed over an intermediate layer of water residing atop the sand and any other debris or particulate on the tank floor 17. The natural process does not result in complete separation, and so it will be appreciated that the top 'oil layer' is not entirely composed purely of clean oil, but will contain some sand and water content, just as the water layer is not entirely devoid of oil and sand.
As shown a burner tube 28 may extend into the first space of the tank interior in a known manner for heating of the production fluid contents, which is known to aid in the separation of the oil/water emulsion and sand mixture. The burner tube may be situated at an intermediate height above that of both the tank inlet 24 and the horizontal leg 16b of the downcomer, but well below that of the downcomer inlet 20. Injected chemical treatments to aid in the separation process may also be employed in a known manner.
As the separation process progresses during filling of first interior space with the incoming production fluid mixture, the top oil layer rising toward the upper end 16a of the baffle 16 on the first side thereof eventually reaches the downcomer inlet 20, at which point the relatively clean oil of this upper layer will begin to drain down through the downcomer, thus feeding into the second interior space on the second side of the baffle near, but spaced above, the tank floor 17. As mentioned above, this 'relatively clean' oil from the first side is expected to still contain some contaminants, but the natural separation process will continue on this second side of the baffle. A second burner tube 30 may extend into the second space of the tank to aid in this further separation of the production fluid that has already undergone a first stage of separation in the first space. Accordingly, remaining sand or other debris will settle out to the floor of the second internal tank space, with the cleanest oil again rising toward the top of the space.
By delivering the fluid from the first space into the second space near the lower end of the second space, as opposed to having it overflow over the top of the baffle, the top layer of oil in the second space will be the cleanest oil in the tank, at least until the first tank space tank is filled to a level exceeding the top end of the baffle, as this oil has undergone separation in both spaces of the tank, and the first-stage oil from the first space has not yet overflowed the baffle onto this cleanest second-stage oil at the top of the second space. Accordingly, the Figure 1 shows the tank outlet 26 situated relatively high in the second interior space of the tank for evacuation of the cleanest oil from the tank.
While Figure 1 shows the outlet 26 schematically as a conduit in the circumferential tank wall at the desired draw-off height, it will be appreciated that outlet configurations are known whereby pipe conduits within the tank are assembled with control valves allowing the operator to draw off tank content from a variety of different positions within the tank, and such means may be employed in a tank of the present invention. For example, alternative outlet 26' is shown as an open end of a length of piping extending down from this opening to a chamber equipped with control valving and a suitable coupling point for a connection of a discharge line to draw the clean oil out of the tank from the upper level of the second space. Use of an internal chamber to contain valves, heaters, level controls and spill containment means is known in the art, as exemplified by U.S. Patent No.

assigned to Enviro Vault Ltd, in which sample taps at varying heights in the tank allow drawing off of the fluid from different levels therein.
Figure 1 shows the downcomer outlet 22 situated at an elevation below the second burner tube 30, but also notably spaced above the tank floor 17.
This 5 way, the outlet 22 will tend to feed the oil from the upper layer of the first space into the lower end of an oil layer accumulated in the second space, as opposed to directing this oil into the sand or water accumulation layers nearer the bottom of the second space.
Figure 2 shows a second embodiment oilfield production tank 10' of 10 the present invention that differs from the first only in the structure of the divider and fluid-transfer arrangement between the two spaces. Instead of a single baffle and a downcomer, a pair of baffles 32, 34 are used to both separate the two spaces of the tank interior and provide the top-to-bottom fluid transfer from the first space to the second space. The first baffle 32 has its lower end attached to the tank floor 17 and forms a solid barrier over its full area. The second baffle 34 has its upper end 34a situated in accordance with that of the single baffle 16 of the first embodiment. The upper end 32a of the first baffle 32 is situated at a slightly lower elevation than that of the second baffle 34. The second baffle is a split baffle mounted in a manner leaving an open space between its lower end 34b and the tank floor 17, or having on or more openings in it at its lower end so as to likewise be substantially open at the tank floor 17.
The gap 36 between the two parallel vertical baffles defines a fluid transfer passage having a passage inlet 38 that opens vertically into the first space of the divided tank at the top end 32a of the first baffle 32, and a passage outlet 40 that opens horizontally into the second space at the lower end 34b of the second baffle. The two baffles thus cooperate together to provide both the space-dividing function and the fluid transfer function of the baffle and downcomer combination of the first embodiment.
Arrangements for guiding the upper level of oil from the first space to near the bottom of the second space may employ means other than the illustrated L-shaped downcomer piping or inter-baffle gap and still provide the equivalent functionality. In the embodiment of Figure 1, the downcomer pipe may be removable, and paired with a pluggable pipe-accommodating opening in the baffle, whereby the downcomer can optionally be removed and the two spaces entirely separated over the full baffle area, for example for filling of the two separated spaces by two different wells. The illustrated embodiments feature baffles that stop short of the top of the tank in order to allow equalization between the two spaces when once space is filled up to the top of the baffle, where the fluid content of that space would thereby overflow into the other space over the top of the baffle. Other embodiments may feature a full height baffle arrangement reaching fully to the top of the tank, providing entirely full separation of the spaces other than that the top-to-bottom fluid transfer passage provided by the downcomer or other means.
Figure 3 illustrates a third embodiment which, like the first embodiment, employs a downcomer 118 or riser with horizontal and vertical legs or sections that cooperate to transfer fluid from near the top of the first space to nearer the bottom of the second space. However, the downcomer 118 differs from that of the first embodiment in that its vertical leg resides entirely on the second side of the upright baffle instead of the first. That is, the downcomer inlet is defined by a horizontally-opening end 120 of a horizontal pipe leg 118a of the downcomer that is engaged in an opening of the upright baffle 116 so as to pass therethrough in order to transfer fluid from the downcomer inlet 120 on the first side of the baffle 116 to the second side of the baffle. Alternatively, the horizontal pipe leg 118a may be disposed entirely on the second side of the upright baffle and coupled to the baffle in a sealed manner around the opening therein without passing through the opening, thereby placing the downcomer inlet 120 at the plane of the upright baffle 116.
From the height at which the horizontal pipe leg 118a is engaged with the opening in the baffle, a vertical pipe leg 118b then turns vertically downward from the horizontal pipe 118a in order to run downward along the second side of the baffle toward the lower elevation of the downcomer outlet 122, which may be defined by a second horizontal pipe leg 118c joined, integrally or otherwise, to the bottom end of the second pipe leg 118b in order to extend away from the baffle116 toward a more central area of the second interior tank space. In this embodiment, the fluid entering the downcomer is not guided downward through the cooler lower layers below it on the first side of the baffle by the vertical pipe leg, but instead travels downward through the warmer fluid on the second side of the baffle, thus acting to further heat the fluid as it moves through the downcomer piping in order to improve the heat-induced separation or cleaning action by using the already twice burner-heated fluid on the second side of the baffle to further warm the once burner-heated fluid moving through the downcomer, and to conserve heat energy by not passing the downcomer fluid through the cooler lower layers in the first space. As with the first embodiment, the pipe legs may be integral sections of a unitary length of bent pipe, or may be different pipes coupled together, for example by suitable corner or elbow fittings.
In addition, each leg of the downcomer need not be purely vertical or horizontal, but such orientations are described herein to distinguish lateral lengths of piping that are intended to convey fluid more horizontally than vertically from upright lengths of piping that are intended to convey fluid more vertically than horizontally.
Each pipe leg or section also need not be purely linear in form in its reach to or from a respective corner between horizontal and vertical legs.
Figure 4 illustrates an optional control mechanism 200 of a type usable on the tank of the first embodiment where the downcomer features a vertical pipe leg 18a with an open top end 20 on the first side of the baffle 16. The mechanism 200 is used control the height at which the downcomer inlet is effectively defined, thus controlling the level to which the first interior space of the tank is filled before fluid starts to transfer into the second space on the other side of the baffle.
The mechanism features a cylindrical sleeve 202 of inner diameter slightly greater than the outer diameter of the vertical pipe leg 18a so as to telescopically fit over the vertical pipe leg 18a in coaxial alignment therewith from the top end 20 thereof. An annular seal 203 is provided between the vertical pipe leg 18a and the sleeve 202 to allow a sliding interface between them while maintaining a fluid-tight seal of the annular space between them. The sleeve 202 extends a vertical distance upwardly beyond the open top end 20 of the vertical pipe leg 18a.

Near the top end of the sleeve 202, one or more slot or window openings 204 open into the hollow interior of the sleeve through its cylindrical wall. These openings 204 define the effective downcomer inlet by which fluid enters the downcomer for guidance of the fluid onward through the open end 202 of the vertical leg thereof 18a. A top end of the sleeve is closed off by a cap 206 fixed thereon. Inside the sleeve, the cap features a resilient material on the underside thereof that faces downward toward the open top end 20 of the vertical leg 18a of the downcomer.
Axial sliding of the sleeve 202 along the vertical pipe leg 18a allows movement of the sleeve into an out off a lowermost position in which the cap 206 fits over the open top end 20 of the pipe leg 18a and seals this end closed by way of a conforming fit of the resilient sealing material on the underside of the cap with the annular end face of the pipe leg 18a. Lifting of the sleeve from this pipe-closing position initially brings the slot or window openings 204 up into positions that cross the elevation of the open end 20 of the pipe leg 18a, and then raises the openings 204 even further to heights that are spaced upwardly beyond the horizontal plane of the open end 20 of the pipe leg 18a. Controlled raising of the sleeve can thus control the amount of window or slot area of the sleeve that is open above the top end of the vertical pipe leg 18a, and then control how far above this vertical pipe leg 18a the window or slots openings 204 are located. Accordingly, the position of the sleeve can control how fast the fluid enters the downcomers upon reaching the windows or slots of the sleeve when they are positioned at a height crossing the plane of the open top end of the vertical leg 18a of the downcomer, or used to control the effective height of the downcomer inlet by controlling the distance by which the windows or slots 204 of the sleeve 202 are spaced above the open top end 20 of the downcomer's vertical pipe leg 18a.
The position of the sleeve 202 is controlled by an actuator linkage 208 featuring a control lever 210 carried atop the tank roof, for example as defined at the 5 exterior top side of the top wall 14 of the tank. A pivot bracket 212 mounted to the tank roof features a pair of vertically extending lugs between which the control lever 210 passes, and a pivot pin passes horizontally through the lugs and control lever 210, whereby the lever is supported for pivotal movement about a horizontal pivot axis. An intermediate link 214 has an upper end thereof located outside the tank 10 and pivotally coupled to an output end of the control lever 210, and a lower end coupled to the sleeve 202 inside the tank on the first side of the upright baffle 16.
The control lever features a handle 216 at an input end thereof opposite the output end at which the intermediate link 214 is attached, whereby manual raising of the handle 216 at a distance to one side of the pivot bracket 212 causes lowering of the 15 intermediate link 214, and the sleeve 202 carried thereby, on the second side of the pivot bracket 212.
A locking device features an upright roof-mounted plate 218 residing aside the plane of the control lever and featuring a series of through holes through which a suitable locking pin can be engaged into a corresponding diametric through-hole of the control lever 210 in order to lock the lever in a selected one of a number of different positions, each of which corresponds to a different respective predetermined position of the sleeve 202 on the vertical leg 18a of the downcomer.

Alternate actuation systems for effecting movement of the sleeve and locking the same in a selected position may be employed, and may include actuators of a powered configuration, as opposed to the manually powered control linkage of the illustrated embodiment. However, the use of a manually powered level control mechanism avoids the need for a power source to drive an electric, hydraulic or pneumatic actuator. Where a powered actuator is used however, manual control still may be effected from outside the tank, for example by a manually operated control valve of a hydraulic circuit or an electronic controller, whether onsite or remote, hard wired or wireless, of an electric, electric-over-hydraulic, or electric-over-pneumatic actuation system.
Figure 5 illustrates another type of optional control mechanism 300 for use on the third embodiment tank of Figure 3, where the downcomer features a horizontal pipe leg 118a with a horizontally-opening end 120 on the first side of the baffle 16. The mechanism 300 is again used to control the height at which the downcomer inlet is effectively defined, thus controlling the level to which the first interior space of the tank is filled before fluid starts to transfer into the second space on the other side of the baffle.
This embodiment of the control mechanism uses a ninety degree or other angled pipe fitting 302 to define a tubular elbow of fixed shape having one end thereof coupled to the end 120 of the horizontal pipe leg 118a by a swivel joint 304, whereby the elbow fitting 302 can be rotated about the central horizontal axis of the horizontal pipe leg 118a that lies concentrically with the coupled end of the elbow fitting 302. The angled shape of the elbow fitting places the free open end 306 of the fitting at position spaced radially outward from this axis in an orientation causing the free end 306 of the fitting to face a direction having at least a radial component relative to the horizontal axis of the swivel joint. In the illustrated embodiment, in which a ninety degree elbow is used, the direction faced by the open free end 306 of the fitting is purely radial relative to the swivel axis, and the swivel axis is oriented purely horizontally. This provides a maximized vertical range of heights throughout which the free end 306 of the pipe fitting 302 can be disposed in its rotation about the swivel axis. However, other embodiments in which an elbow angle other than ninety degrees, or a pipe leg and swivel axis that is somewhat angled and not purely horizontal, may also be employed while still obtaining height adjustability of the free end of the elbow fitting, which effectively defines the downcomer inlet in this embodi ment.
Figure 5 shows the elbow fitting 302 in a vertical plane with the free end 306 facing vertically upward, thus setting the downcomer inlet at its maximum possible height above to the open end 120 of the horizontal pipe leg 118a of the downcomer. By swiveling the elbow fitting 180-degrees from this position, so as to lie in the same vertical plane but with the free end 306 pointing downward, the downcomer inlet is set at its minimum possible height disposed below the open end 120 of the pipe leg 118a.
A cable, rope or chain actuator 308 is used to control the position of the elbow fitting 102. A flexible elongated member 310 such as a rope or chain is entrained about a roller or guide member 312, such as a pulley, mounted externally of the tank atop the roof thereof. After passing over the guide or roller member 312, =

the flexible rope or chain extends downwardly into the tank interior on the first side of the upright baffle 116 through a suitable opening in the top wall 14 of the tank.
Inside the tank, an output end of the flexible member 310 is attached to the pipe fitting 302 at a radial distance outward from the swivel axis, preferably adjacent the free open end 306 of the fitting. From this upright span of the flexible member passing upward through the top wall of the tank from the pipe fitting, the flexible member 310 is redirected laterally outward from this rooftop location toward the perimeter of the tank roof, where another roller or guide may direct the flexible member downward along the side of the tank from the roof for control of the actuator from ground-level.
A user can pull the input end of the flexible member in order to pull upward on the free end 306 of the elbow fitting 302, thereby swiveling the elbow fitting in a direction raising the location of the free end thereof. The control end of the flexible member may be attached to a winch or reel, whereby rotation of the winch or reel in a winding direction that draws more of the flexible member onto the winch or reel performs this inlet-raising pulling action on the elbow fitting, and a brake or lock mechanism of the winch or reel is used to lock the selected position of the elbow fitting by locking the winch or reel against rotation. Use of a manually powered reel avoids need for a power source to operate a powered winch. On the other hand, a powered actuator may provide increased ease of operation, and optional electronic control from remote locations. Alternatively, actuator mechanisms other than the described cable, rope or chain actuator may alternatively be employed to control swiveling of the elbow fitting to adjust the downcomer inlet height.
Additional description and commentary on one or more embodiments are provided as follows.
A baffle installed internally in the tank separates the tank into two compartments or chambers in order to isolate the fluid until it reaches the height of the internal baffle riser or downcomer, which brings the emulsion off the top of one side to the bottom of the second section to reduce the contaminants in the emulsion, such as bitumen, sand and water (BS&W). The emulsion flows in the tank inlet, and the oil rises and flows through the downcomer into the other section of the tank.
Room above the baffle allows for high fluid/foam equalization in high-level tank situations.
The tank can also allow for two wells to be produced into one tank for cleaning the emulsion and shipping the resulting product. By controlling levels, this system can also be used to test one well or the other. In other words, when producing two wells into the one tank, to meet government testing requirements, one could keep the levels of the two spaces low enough, for example for one day a month, and direct the output of each well into a different tank space for separate testing of each by keeping the levels below the downcommer inlet so that no flow goes between the separated tank spaces. As another option, by removing the downcomer, which operates as an equalizer once the first space has been sufficiently filled to reach the downcomer inlet, two wells can be produced into the one tank with the open area at the top being used to avoid external tank overflow by having the filled space overflow into the other space, whereupon continued filling can rise up into the headspace of the tank.
The invention can be used at single oil wells, oil well pad sites, and oil well treating facilities. While the illustrated embodiments feature a cylindrical tank 5 divided into substantially equal halves, other tank shapes and relative sizing of the divided spaces may alternatively be employed.
Since various modifications can be made in my invention as herein above described, and many apparently widely different embodiments of same made within the spirit and scope of the claims without department from such spirit and 10 scope, it is intended that all matter contained in the accompanying specification shall be interpreted as illustrative only and not in a limiting sense.

Claims (20)

1. An oilfield production tank comprising:
a tank enclosing an interior;
a divider arrangement mounted at a location within the tank and dividing a first space of the interior from a second space of the interior over a majority of a height of the tank at the location of the divider;
a fluid passage having a fluid passage inlet positioned within the first space of the interior of the tank on a first side of the divider at a first height nearer an upper end of the divider than a lower end of the divider, and a fluid passage outlet that opens into the second space of the interior of the tank on a second side of the divider at a second height that is lower than the first height;
a tank inlet opening into the interior of the tank on the first side of the divider for ingress of produced well fluid into the tank through said tank inlet;
a tank outlet opening into the interior of the tank on the second side of the divider for egress of fluid from the tank through said tank outlet.

2. The oilfield production tank of claim 1 wherein the divider arrangement comprises an upright baffle.

3. The oilfield production tank of claim 2 wherein the fluid transfer passage is defined by a downcomer that is engaged with an opening in the baffle to deliver fluid from the first space to the second space through the upright baffle at said opening therein..

4. The oilfield production tank of claim 3 wherein the downcomer extends through the opening.

5. The oilfield production tank of claim 3 wherein the downcomer engages with the opening in the baffle at a height closer to the fluid passage inlet than to the fluid passage outlet, and runs downwardly from said height on the second side of the upright baffle.

6. The oilfield production tank of any one of claims 1 to 5 comprising a control mechanism operable to adjust the first height at which the fluid passage inlet is located in order to control a fluid level to which the first space will fill before reaching the fluid passage inlet.

7. The oilfield production tank of claim 6 wherein the control mechanism comprises:
a sleeve slidably disposed over an upright length of pipe that forms a portion of the fluid passage; and at least one inlet opening that opens into an interior of said sleeve at an area of the sleeve that is movable within a range of heights disposed above the top end of the upright length of pipe.

8. The oilfield production tank of claim 7 wherein the control mechanism further comprises an actuator operable to raise and lower the sleeve to adjust a position of the inlet opening of the sleeve relative to the top end of the upright length of pipe.

9. The oilfield production tank of claim 8 wherein the actutator of the control mechanism comprises a control linkage having an input end and an opposing output end coupled to the sleeve for sliding movement thereof along the length of upright pipe under movement of the input end of the control linkage.

10. The oilfield production tank of claim 8 wherein the actutator of the control mechanism comprises a control lever having an input end, an opposing output end and a pivot point between the input and output ends, the output end being coupled to the sleeve for sliding movement thereof along the length of upright pipe under pivotal movement of the input lever about the pivot point.

11. The oilfield production tank of claim 9 wherein the input end of the control linkage is positioned externally of the tank for manual manipulation of the input end from outside the tank.

12. The oilfield production tank of claim 6 wherein the control mechanism comprises a tubular elbow having a first end thereof that is coupled by a swivel joint to an inlet end of a lateral length of pipe that forms part of the fluid passage to enable pivoting of the tubular elbow about an axis of the swivel joint to adjust a height of an opposing second end of the tubular elbow relative to the inlet end of the lateral length of pipe.

13. The oilfield production tank of claim 12 wherein the lateral length of pipe extends through the divider arrangement from the first side thereof to the second side thereof, at which the lateral length of pipe is joined to an upright section of pipe running downwardly along the divider arrangement toward the fluid passage outlet.

14. The oilfield production tank of claim 12 or 13 wherein the control mechanism comprises an actuator comprising an elongated flexible lift member having an output end thereof coupled to the tubular elbow from above for raising of the second end of the tubular elbow under pulling of the elongated flexible lift member.

15. The oilfield production tank of claim 14 wherein the elongated flexible lift member is routed to an exterior of the tank for operation of the control mechanism from outside the tank by manually driven pulling of the elongated flexible lift member.

16. The oilfield production tank of any one of claims 6 to 15 wherein the control mechanism comprises a locking device operable to lock a position of the fluid passage inlet at a selected height.

17. The oilfield production tank of any one of claims 1 to 16 comprising a fluid pathway between the first and second spaces at an elevation spaced above the inlet of the fluid transfer passage.

18. The oilfield production tank of claim 17 wherein the upper end of the divider arrangement is spaced below an upper end of the interior of the tank to leave an open space defining the fluid pathway between the upper end of the divider arrangement and the upper end of the interior of the tank.

19. The oilfield production tank of any one of claims 1 to 18 wherein the divider arrangement reaches fully to a bottom of the interior of the tank in order to separate the first and second spaces entirely from one another over an area spanning from the bottom of the interior of the tank to the upper end of the divider arrangement.

20. The oilfield production tank of any one of claims 1 to 19 wherein the tank inlet is disposed at a lower elevation than the fluid passage inlet.