Water surge interface slot for three phase separator

A three phase separator to separate a fluid into three phases. A horizontal tank forms a fluid container having an inlet to the container in order to permit entry of a three phase fluid. An oil box within the fluid container includes a bottom and at least one baffle separating the oil box from the fluid container. A water box within the fluid container includes a bottom and at least one baffle separating the water box from the container. A water removal mechanism is in communication with the water box to draw water therefrom. An oil removal mechanism is in communication with the oil box to draw oil therefrom. A gas outlet permits removal of gas from the fluid container. A slot through the baffle of the water box permits entry of water from the fluid container into the water box in the event of a water surge.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is directed to an apparatus and a method to provide a three phase separator to separate well stream fluid into three phases—liquid hydrocarbon, water (or brine) and gas. In particular, the present invention is directed to an apparatus and method for a three phase separator for separating well stream fluid having a water surge interface slot to accommodate entry of fluid in the event of a water surge.

2. Prior Art

Three phase separators are well known in the energy industry to separate a fluid flow delivered from a subterranean well or wells. It is also known that wells flow at different rates and that the composition of the fluid may vary from time to time. If the producing pressure becomes so low that the well will not produce at a desired flow rate, a variety of artificial lift methods may be employed. In one type of artificial lift method, plunger lift, periodic surges of liquids are produced.

A stream of fluids is delivered from the well. The purpose of the three phase separator is to separate an incoming feed or flow into a gaseous phase and two liquid phases—a lighter liquid phase primarily composed of liquid hydrocarbons and a water phase primarily composed of water or brine. The specific gravity of the hydrocarbon liquid phase is less than the water phase.

The three phase separator may take various configurations, but generally are either classified as horizontal or vertical or some combination thereof. In one design, a vessel extends and is normally horizontal. A cylindrical wall or shell of the vessel has opposed closed ends. The size of the vessel will vary depending on the flow conditions and the desired retention time. The three phases separate generally by gravity with the gaseous phase migrating to the top of the normally horizontal vessel. Below the gaseous phase, the liquid separates into two phases with the liquid hydrocarbon phase above the water phase. The gaseous phase is removed from the separator and is delivered for further processing or is flared-off. The water phase is removed from the separator and may be pumped back into the subterranean formation or otherwise disposed of. The liquid hydrocarbon phase is removed from the separator and is delivered for further processing.

The fluids in the separator are under pressure and valves and sensors may be employed as liquid level control mechanisms to control and remove the liquids. The liquid hydrocarbon phase and the water phase may be separated into compartments within the vessel.

There have been various designs in the past for three phase separators. For example, Polderman (U.S. Pat. No. 6,537,458) shows one example of a three phase separator. If during any time period, the gaseous phase increases, then the liquid level in the separator will go down while the gas level will increase. In the event of a surge or pulse of liquid into the separator, water may be permitted to flow into the separator box or chamber reserved for oil which frustrates the purpose of the three phase separator.

Coggins et al. (U.S. Pat. No. 4,208,196) discloses a horizontal separator inFIG. 1with baffles to separate the hydrocarbon liquid from water phase.

Accordingly, it would be advantageous to provide an apparatus, method, and system for a three phase separator that may be deployed near the location of a production well or wells while accommodating a wide variety of flow conditions.

It would be advantageous to provide an apparatus, method and system for a three phase separator to accommodate fluid surges or pulses in the level of liquid into a separator.

Additionally, it would be advantageous to provide an apparatus, method and system for a three phase separator that avoids entry of the water phase into the hydrocarbon liquid phase.

SUMMARY OF THE INVENTION

The present invention is directed to a three phase separator to separate fluids under pressure into three phases. The three phase separator of the present invention includes a substantially horizontal tank having an axis which forms a fluid container. The axis of the container is generally parallel to ground level. The fluid container has a substantially cylindrical shell with a pair of opposed, substantially spherical ends forming a closed container.

A fluid inlet permits entry of a fluid under pressure from a well or wells into the fluid container. An optional splash plate within the container adjacent the inlet may be provided to reduce the flow of velocity of the incoming fluid.

Once inside the container, the fluids will tend to separate in directions perpendicular to the axis of the container.

The three phase separator includes an oil box within the fluid container. The oil box includes at least one sidewall which is perpendicular to the axis, a bottom which is parallel to the axis, and a baffle which is perpendicular to the axis. The sidewall and baffle each extend across the cylindrical shell and are secured thereto. Accordingly, the cylindrical shell, the sidewall, the bottom, and the baffle together form an open topped compartment within the fluid container. An adjacent water box includes a sidewall which is perpendicular to the axis, a bottom which is parallel to the axis, and a baffle which is perpendicular to the axis. Accordingly, the cylindrical shell, the sidewall, the bottom, and the baffle together form an open topped compartment within the fluid container.

A siphon nipple in the form of a tube extends through the bottom of the water box so that it is in fluid communication with the container. The siphon nipple is threadably attached to the bottom so that the level of an upper end of the siphon nipple is adjustable by rotating the siphon nipple. A gas outlet is provided in the fluid container so that the gaseous phases separated out in the separator may be removed.

A water removal mechanism is in fluid communication with the water box through a tube. When the level of water in the water box reaches a certain level, the water control valve is opened to release water under pressure.

An oil removal mechanism is in fluid communication with the oil box through a tube. When the level of oil in the oil box reaches a certain level, the oil control valve is opened to release oil under pressure.

A surge interface slot through the baffle of the water box permits entry of water from the fluid container into the water box. As the fluid container begins to fill with fluid, the gaseous phase will migrate above the level of the axis for removal through the gas outlet. Initially, the liquid phases will pass beneath the bottom of the oil box and the bottom of the water box.

As fluid continues to enter the container, a water seal will be formed preventing oil from moving under the bottom of the oil box and the bottom of the water box and adjacent the water baffle. As the overall level of liquid continues to rise, only water passes beneath the bottoms and into the siphon nipple.

As the level of liquid continues to rise and exceeds the level of the baffle of the oil box, oil will spill over into the oil box. Since the oil separates above the water or brine level, no water or brine will be allowed to enter the oil box.

The water level will continue to rise until the oil/water interface level is controlled by the height of the opening of the siphon nipple into the water box.

The baffle of the water box includes a surge interface slot therethrough. In the event of a slug or surge of water into the fluid container, the surge interface slot will operate to prevent the water/oil interface level from exceeding the level of the oil baffle, thus preventing any water from entering the oil box. When the water level reaches the level of the interface slot, water will be permitted to flow from the container through the interface slot and into the water box.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As seen in the perspective view inFIG. 1, a three phase separator of the present invention includes a substantially horizontal tank having an axis12which forms a fluid container10. The axis12of the container is generally parallel to ground level (not shown). Framework (not shown) may be provided to support the separator. Optional equipment (such as heating coils or shells) might also be employed within the spirit of scope of the present invention.

The fluid container10has a substantially cylindrical shell with a pair of opposed, substantially spherical ends forming a closed container10. A fluid inlet14permits entry of a fluid under pressure from a well or wells (not shown) into the fluid container10as shown by arrow20. It will be appreciated that the inlet14may be located in alternate locations within the spirit and scope of the invention. An optional splash plate16within the container10adjacent the inlet14may be provided to reduce the flow velocity of the incoming fluid. A normally closed entry port18or entries may be provided to permit access into the fluid container10for maintenance and repair.

As will be seen, once inside the container10, the fluids will tend to separate in directions perpendicular to the axis as shown by arrows38.

The three phase separator includes an oil compartment, chamber or box22within the fluid container10. The oil box22includes at least one sidewall24which is perpendicular to the axis12, a bottom26which is parallel to the axis12, and a baffle28which is perpendicular to the axis. The sidewall24and baffle28each extend across the cylindrical shell and are secured thereto, such as by welding. Accordingly, the cylindrical shell, the sidewall24, the bottom26and the baffle28together form an open topped compartment within the fluid container10.

An adjacent water compartment, chamber or box30includes a sidewall24which is perpendicular to the axis12, a bottom32which is parallel to the axis12, and a baffle34which is perpendicular to the axis. In the present case, the sidewall24is shared between the oil box22and the water box30. Accordingly, the cylindrical shell, the sidewall24, the bottom32and the baffle34together form an open topped compartment within the fluid container10.

A siphon nipple36in the form of a tube extends through the bottom32of the water box30so that it is in fluid communication with the container10. The siphon nipple36is threadably attached to the bottom32so that the level of an upper end of the siphon nipple is adjustable by rotating the siphon nipple.

There are, thus, three distinct compartments within the three phase separator, with the oil box22and the water box30within the larger fluid container10.

A gas outlet42is provided in the fluid container10so that the gaseous phase separated out in the separator may be removed as shown by arrow44. It will be appreciated that the gas outlet42may be located in alternate locations above the liquid levels to remove the gas.

A water removal mechanism50is in fluid communication with the water box30through a tube. The water removal mechanism50includes a liquid level sensor within the water box30and a water control valve. The liquid level sensor may be of a mechanical or other type to sense the liquid level in the water box. When the level of water in the water box reaches a certain level, the water control valve is opened to release water under pressure as shown by arrow56.

The control valve may be a mechanical or pilot operated valve actuated by a float or a diaphragm control valve actuated by a displacement float. Other types of control valves may be employed within the spirit and scope of the invention.

An oil removal mechanism60is in fluid communication with the oil box22through a tube. The oil removal mechanism60includes a liquid level sensor within the oil box and an oil control valve. The liquid level sensor may be of a mechanical or other type to sense the liquid level in the oil box. When the level of oil in the oil box reaches a certain level, the oil control valve is opened to release oil under pressure as shown by arrow66.

A surge interface slot70through the baffle34of the water box30, permits entry of water from the fluid container10into the water box30. The level of the surge interface slot is positioned above the level of the siphon nipple and below the level of the oil box baffle.

FIGS. 2 through 6sequentially illustrate the process of the present invention.

Referring initially toFIG. 2, as the fluid container10is beginning to fill, the liquid phases will gather at the base of the container below the axis12. Conversely, the gaseous phase will migrate above the level of the axis for removal through the gas outlet42. Initially, as shown inFIG. 2, the liquids will pass beneath the bottom26of the oil box22and beneath the bottom32of the water box30.

As fluid continues to enter the container10and the liquid phases separate, a “water seal” will be formed preventing oil from moving under the bottom26of the oil box and the bottom32of the water box and adjacent the water baffle34.

As seen inFIG. 3, the overall level of liquid continues to rise. Only water passes beneath the bottoms26and32and into the siphon nipple36.

FIG. 4shows the overall level of liquid rising.

As seen inFIG. 5, as the level of liquid exceeds the level of the baffle28of the oil box22, oil will spill over into the oil box22. Since the oil separates above the water or brine, no water or brine will be allowed to enter into the oil box22.

The water level will continue to rise until the oil/water interface level is controlled by the height of the opening of the siphon nipple36. As seen in the water box30inFIG. 5, water will flow from the fluid container10into the siphon nipple36, out of the siphon nipple and into the water box30. The water liquid level control mechanism will operate to open a valve to discharge water from the fluid container.

As best seen inFIG. 6, the baffle34of the water box30includes a surge interface slot70. In the event of a slug or a surge of water into the fluid container10, surge interface slot70will operate to prevent the water/oil interface level from exceeding the level of the oil baffle28, thereby preventing any water from entering the oil box. As best seen inFIG. 6, the oil/water interface level has risen, since there is too much pressure drop through the siphon nipple for the water to be transferred quickly into the water box. When the water level reaches the level of the interface slot70, water will be permitted to flow from the container into the water box. When the surge or slugging condition is over, the separator returns to a steady state condition ofFIG. 5.

The level of the surge interface slot is positioned above the level of the siphon nipple and below the level of the oil box baffle.

Whereas, the present invention has been described in relation to the drawings attached hereto, it should be understood that other and further modifications, apart from those shown or suggested herein, may be made within the spirit and scope of this invention.