Patent Abstract:
An improved water-oil separation apparatus with a separation vessel and associated water leg having internal inlet piping that feeds fluids to an engineered degassing boot, having an engineered degassing boot that is more effective in removing entrained gases from the incoming fluid stream, having an umbrella shaped upper baffle instead of an inverted umbrella shaped upper baffle, having an improved oil collection bucket or weir, having a much improved inlet water spiral distribution apparatus, having an improved water leg design, and having a water leg with a functional height that is externally adjustable to make it easier to regulate the oil-water interface level within the separation vessel.

Full Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a separation apparatus having a water-oil separator and associated water leg for separating gas, water and oil mixtures where the mixture contains a significant amount of water and a small amount of oil to be separated and recovered from the water. This invention is generally intended for use in treating fluid streams relating to petroleum oil and gas production. 
     2. Description of the Related Art 
     The present invention improves over the separation apparatus taught in Applicant&#39;s U.S. Pat. No. 5,073,266. The teaching of that patent is hereby included by reference. 
     Specifically, the present invention includes improvements in having internal inlet piping that feeds fluids to an engineered degassing boot, in having an engineered degassing booth that is more effective in removing entrained gases from the incoming fluid stream, in having an umbrella shaped upper baffle instead of an inverted umbrella shaped upper baffle, in having an improved oil collection bucket or weir, in having an improved water leg design, and in having a water leg with a functional height that is externally adjustable to make it easier to regulate the level of the oil-water interface within the separation vessel. 
     It should be understood that the oil-water interface may not be a clearly defined line due to the fact that the separation zone contains a mixture of oil and water. 
     In applications where inlet fluids include significant quantities of gas, it is necessary to install a system designed to separate the gas from the liquids in order to prevent gas evolution related mixing in the liquids separation section downstream. The generic system is identified as a “de-gassing boot”; however these have always been and still are just empty vertical pipe liquids-gas “separators” where no engineering expertise was ever applied. Offsetting this, the present invention utilizes a similar vertical vessel with engineered internals. These internals absorb the momentum of the inlet fluids, redirecting their flow into a progressively thinner layer of liquids so the entrained gas can more readily escape. 
     Vertical flow diverters provided within the de-gassing boot in association with the fluid inlet spread the liquids out inside the de-gassing boot. The liquids then gravity flow down an inclined baffle provided within the de-gassing boot and at the end of the inclined baffle the liquids cascade onto an opposing inclined plate provided within the de-gassing boot which serves to further thin the stream for even more efficient gas-liquids separation. 
     Also, the present vessel is unique to the de-gassing boots on most previous vessels including the vessel taught in the &#39;266 patent in that the total fluids inlet and the gas outlet are designed to be installed internal to the structure to avoid the safety hazards of having to install these piping assemblies in the field at dangerous elevations above OSHA minimums. Installing this piping in the factory during fabrication simplifies field installation and eliminates concerns for the installation of field piping at heights. This also eliminates the need for external insulation, as the inside piping prevents winter time freeze ups. 
     The invention of the &#39;266 patent mechanically failed within two years of being placed in operation because the upper baffle, which was shaped like an upside-down umbrella, filled with heavy sand and solids which caused it to collapse within the vessel. The present invention has modified this design by inverting the upper baffle so that it does not fill with sand and solids. 
     While the vessel of the &#39;266 patent was originally conceived as a skim tank dedicated to the skimming of small amounts of oil from large quantities of produced oilfield water, many users have recently requested that it be redesigned to provide a more significant oil layer to aid in the separation of water from the stored (skimmed) oil while still incorporating the skim tank design and oil-from-water separation efficiencies. 
     In order to do this the vessel had to be altered by either increasing the height of the vessel to provide additional oil storage space and maintain the skimming abilities designed into the original &#39;266 vessel or an oil collection system had to be designed into the original &#39;266 vessel which used only a simple side-mounted nozzle on the vessel to overflow oil. 
     The side mounted connection provided no measure of uniform oil collection necessary for the desired oil dehydration function. 
     The original &#39;266 vessel was conceived as a 20′ high vessel. In order to accommodate crude oil dehydration, that height had to be increased 4-10 feet, depending on the ease of dehydration according to Stokes&#39; Law. 
     In order to accomplish the dehydration process, the crude oil layer must be 1) uniformly distributed, 2) quiescent, and 3) remain in the vessel for the maximum period of time. All of these factors are dependent on distribution of the incoming crude oil throughout the cross section of the vessel via a newly redesigned high efficiency inlet distributor, and the newly designed oil collection system (s). 
     When crude oil is light and water-from-oil separation is comparatively easy, the first of two different oil collection systems is used. It is a large diameter spillover bucket type collector concentrically located in the center of the vessel 1-2′ from the top. The diameter is fixed at 5′ which produces a 15.7′ spillover weir. With only 2″ of crest height (oil level above the weir edge) this engineered oil collector accommodates instantaneous flows of up to 51,360 barrels per day. With a 4″ crest height, the flow can reach 145,440 barrels per day on an instantaneous or sustained basis into the vessel which means it is virtually impossible to flood the vessel and equally impossible to overflow crude oil out of the vessel and into the environment. The result is that less oil is wasted and more stock tank oil is sent to the refinery. 
     When crude oil is heavier, more care must be taken to assure its retention time in order to produce the desired dehydration results. In this case the vessel&#39;s oil collector described above is replaced with a circumferential ring trough. Adding this same feature to the vessel provides the desired results, completely dehydrating the inlet crude, making it ready for sale. 
     The &#39;266 patent touted the use a water leg wherein the water flowed into and up the inside of two concentric pipes. Later hydraulic engineering studies proved the fallacy of this approach as the emphasis on maintaining a more and more constant contact elevation grew. It finally became clear that the original design needed to be reversed to minimize the effect varying flow rates have on the pressure drop through the water outlet piping and water leg. 
     The reason is not obvious, so it is worth an explanation. Remembering that this vessel is designed to remove small quantities of crude oil from large quantities of produced oilfield waters, it is important to understand the condition this oil is likely to be in. This oil remains in the water reaching this vessel because the oil droplets are exceedingly small. According to Stokes&#39; Law of separation, smaller droplets separate at the square root of the separation rate of droplets twice their size. These small droplets have such a slow separation velocity that until they find an area of almost no movement, they stay entrained and dispersed in the water. The present vessel design gives these droplets that area, so the smallest of those oil droplets can accumulate. However, any movement of this area results in a high degree of re-entrainment of these small and fragile oil droplets. 
     Since the water outlet piping and the external water leg determine the variation in the level where these most fragile oil droplets are known to accumulate, this designer began to focus on minimizing any and all elevation or level changes in this layer. To do so the piping had to be enlarged and the water leg itself had to be both enlarged and redesigned. 
     The alteration moves the water out of the vessel through a much larger pipe, since fluids dynamics studies showed this outlet pipe to be a serious bottleneck restricting flow. By enlarging the outlet pipe the pressure drop is dramatically diminished, thus having the least possible influence on the oil-water contact elevation. 
     Then, the flow in the water leg was reversed so the water leaving the vessel flows into and up the annulus between two pipes where the friction loss is least, and therefore the pressure drop is minimized. The smaller the overall pressure drop through the water outlet piping and water leg, the less the movement at the oil-water interface. The result is far less re-entrainment of separated oils into the effluent water. 
     The &#39;266 patent touted the use a water leg (e.g. a process monometer to control the oil-water contact elevation in a tank or vessel) which employed an internally removable internal part so it could be lengthened or shortened as needed to raise or lower the oil-water interface inside the body of the vessel. The removable part was a friction fit spigot shaped pipe pushed into an opposing angular bell ended pipe. Joining the spigot and the bell made for a junction which was sealed using waterproof grease. The bell and spigot connection and the grease allowed the removable part to be removed. To remove it an operator had to remove a very large and heavy flange to gain access to the insides of the water leg so the upper bell-portion could be removed. Once removed it could be shortened, or a new longer one could be made, thus shortening or raising the spillover height of the water leg itself, and correspondingly, raising or lowering the oil-water interface inside the vessel as was generically known to be necessary to optimize oil recovery and water quality improvements. 
     Over time it became apparent that working on the bell and spigot fittings was so arduous most operators did not bother. This meant fewer barrels of oil entered the economic stream, defeating the entire purpose for the vessel in the first place. The present invention replaces the bell and spigot fittings and all that was associated with them with an externally adjustable adjustment assembly. 
     The function of the external adjustment assembly is to provide a simple mechanism which allows the operator to make adjustments “on the fly” without interrupting his operation. Adjustments to the water leg are necessary to optimize oil recovery, and may be made on a day-to-day basis where an external adjuster is available. 
     The external adjuster is a comprised of an internal slip-sleeve which rides up and down on a smooth pipe section. The sip sleeve is O-ring sealed onto the smooth pipe section to avoid leakage which could/would defeat its function. The slip sleeve is connected to an external jack screw assembly to which a worm gear mechanism is connected. A hand wheel is mated to the worm gear so that turning the hand wheel clockwise raises the slip sleeve while turning the hand wheel counterclockwise lowers the slip sleeve. The worm gear is connected to the slip sleeve by a hollow light-weight rod which is lubricated through a packing gland to completely seal the water leg so no contaminants (water, oil or gas) escape into the atmosphere. 
     The water inside the water leg rises between two concentric pipes, and spills over into the inner pipe at the elevation set by the adjuster. A one inch change in the adjuster elevation translates to a four inch change in the water-oil contact point (elevation) inside the vessel. 
     The real benefit of this adjuster is that it provides a simple way for the operator to adjust the critical level in the vessel. By raising the level the operator send more separated oil to the sales oil tank, improving the cash flow of his company. These fine adjustments also improve the separation of oil from water, maximizing the efficiency of the vessel and minimizing the quantity of otherwise wasted crude oil. Crude oil not separated in the vessel often is disposed of with the waste water into deep disposal wells, where the oil is a plugging agent that tends to plug the well and prevents disposal over the long term. This can cost oil operators millions of dollars in re-drill expenses when a disposal well must be replaced. 
     SUMMARY OF THE INVENTION 
     The present invention improves over the separation apparatus taught in Applicant&#39;s U.S. Pat. No. 5,073,266 by including improvements in having internal inlet piping leading to an engineered degassing boot, in having an umbrella shaped upper baffle instead of an inverted umbrella shaped upper baffle, in having improved oil collection buckets or weirs, in having improved water leg design, and in having an externally adjustable height water leg for regulating the levels within the separation vessel. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side view of a hydrodynamic water-oil separation breakthrough system that is constructed in accordance with a preferred embodiment of the present invention and includes a separation vessel and an associated water leg. 
         FIG. 2  is the separation vessel of  FIG. 1  drawn to shown the internal inlet piping that feeds incoming fluid to the de-gassing boot. 
         FIG. 3  is an enlarged perspective view of the de-gassing boot of  FIGS. 1 and 2  with structures located within the de-gassing boot shown in outline. 
         FIG. 4  is a perspective view of the spiral inlet diffuser from the separation vessel of  FIGS. 1 and 2 . 
         FIG. 5  is a top plan view of the spiral inlet diffuser of  FIG. 4 . 
         FIG. 6  is the separation vessel of  FIG. 2  shown with a bucket type oil collector. 
         FIG. 7  is the separation vessel of  FIG. 6  shown with an alternate serrated top weir type oil collector instead of a bucket type oil collector. 
         FIG. 8  is a front view of a prior art water leg. 
         FIG. 9  is a front view of the water leg of  FIG. 1 . 
         FIG. 10  is an enlarged view of the upper end of the water leg shown within circle  10  of  FIG. 9  and showing the external means for adjusting the height of the internal slip sleeve provided within the water leg. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to the drawings and initially to  FIG. 1 , there is illustrated a hydrodynamic water-oil separation breakthrough system or separation apparatus  10  that is constructed in accordance with a preferred embodiment of the present invention. The system  10  includes a vertical separation vessel  12  equipped with an engineered degassing boot  14  and an attached water leg  16 . 
     As shown in  FIG. 2  by arrow A, a fluid mixture of gas, oil, water and entrained solids enters the vessel  12  at a fluid mixture inlet  18 . The fluid mixture inlet  18  is near ground level  19 . The fluid mixture then flows through internal inlet piping  20  within the vessel  12  to a top  22  of the vessel  12  where the internal inlet piping  20  attaches to a fluid inlet  24  of the engineered degassing boot  14 . The engineered degassing boot  14  is designed to separate gas from the remaining mixture of liquids and solids of the incoming fluid mixture. 
     The internal inlet piping  20  is designed to be preinstalled internally in the vessel  12 , and the fluid inlet  24  to the degassing boot  14  and the degassing boot gas outlet  26  and degassing boot gas equalization line  28  connecting the degassing boot  14  and into the top  22  of the vessel  12  are designed to be connected prior to installation of the vessel  12  to avoid the safety hazards of having to install these piping assemblies  20  and  28  in the field at dangerous elevations above OSHA minimums. Installing these piping assemblies  20  and  28  in the factory during fabrication simplifies field installation and eliminates concerns for the installation of field piping at heights. The internal piping also has the advantage of preventing freeze-ups in the colder winter months. 
     Referring to  FIG. 3 , the flow path through the engineered degassing boot  14  is shown by Arrows B and C. The engineered degassing boot  14  utilizes a vertical degassing tank  30  with engineered internals that is attached at the top  22  of the separation vessel  12 . These internals include vertical flow diverters  32  and inclined baffles  34  that absorb the momentum of the inlet fluids, redirecting their flow into a progressively thinner layer of liquids so the entrained gas can more readily escape. 
     The vertical flow diverters  32  provided within the de-gassing boot  14  in association with the fluid inlet  24  spread the liquids out inside the de-gassing boot  14 . The liquids then gravity flow down a first inclined baffle or plate  34 ′ provided within the de-gassing boot  14  and at the end of the first inclined baffle or plate  34 ′, the liquids cascade onto an opposing second inclined baffle or plate  34 ″ provided within the de-gassing boot  14  which serves to further thin the stream for even more efficient gas-liquids separation. The degassing boot gas equalizer line  28  connects the degassing boot  14  and the top  22  of the vessel  12 , and excess gas accumulating in the top  22  of the vessel  12  and in the degassing boot  14  is removed from the system  10  via a gas vent  36  provided in the top  22  of the vessel  12 . 
     The degassed liquids then flow under the influence of gravity downward within an upper portion  38  of a central tube  40  provided in the vessel  12 , as shown by Arrow D, and exit the central tube  40  at a spiral inlet diffuser  42 , shown in detail in  FIGS. 4 and 5 . 
     The degassed liquids flow through the spiral inlet diffuser  42  which imparts an ever increasing spiral flow path to the liquids as they enter a separation zone  44  of the vessel  12 , as shown by Arrow E. This spiral flow path does two things. 
     First, the spiral flow path slows the flow so that solids contained within the degassed liquids tend to fall out onto a convex top  46  of an umbrella shaped upper baffle  48  that is located just below the spiral inlet diffuser  42 . Because the top  46  of the upper baffle  48  is convex, sand and other solids that fall on it do not accumulate to any great extent on the top  46  of the upper baffle  48 , but instead tend to roll off of the upper baffle  48  and fall to a bottom  50  of the vessel  12  where they can be periodically removed via a manhole  52  provided in the vessel  12 . 
     Second, the spiral flow path provides sufficient retention time and quiescence to allow oil droplets to disengage from the water within the liquid stream and to migrate upward to an oil-water interface  54 , as indicated in  FIG. 2  by Arrow O where the oil eventually migrates into an oil layer  56  located above the oil-water interface  54  due to the difference in density. 
     Excess oil is removed from the oil layer  56  and from the vessel  12  by one of two alternate structures: a bucket type oil collector  58 , as shown in  FIG. 6 , or alternately, a serrated top weir type oil collector  60 , as shown in  FIG. 7 . 
     As shown in  FIG. 6  by Arrows F, oil flows from around the outside of the bucket type oil collector  58  and flows over the top  62  of the bucket type collector  58  at a gas-oil interface  126  located within the vessel  12  to enter the inside  64  of the bucket type collector  58  and out the bottom  66  of the bucket type collector  58  and out of the vessel  12  via an oil outlet  68 . 
     Alternately, as shown in  FIG. 7  by Arrows G, oil within the oil layer  56  flows upward through the open central area of a serrated top weir type oil collector  60  and flows over the serrated top edge  70  of the serrated top weir type oil collector  60  to enter a circumferential oil trough  72  formed between the serrated top weir type oil collector  60  and an interior wall  74  of the vessel  12  and then out of the vessel  12  via the oil outlet  68  that communicates with the oil trough  72 . 
     After exiting the spiral inlet diffuser  42 , as oil is separating and moving upward within the vessel  12 , water separates flows downward around the upper baffle  48 , as shown in  FIG. 2  by Arrow W, and also around an umbrella shaped lower baffle  76 , as shown by Arrow W′, before entering water outlet openings  78  provided just below the lower baffle  72  in a lower portion  80  of the central tube  40 , as shown by Arrow W″. 
     The lower portion  76  of the central tube  40  is isolated via a separating plate  73  from the upper portion  38  of the central tube  40  through which the incoming flow from the degassing boot  14  enters the vessel  12 . Water entering the water outlet openings  78  flows downward through the lower portion  76  of the central tube  40  and out of the vessel  12  at a water outlet  82  provided in the vessel  12 , as shown by Arrows H and H′. As shown in  FIG. 1 , the water outlet  82  is connected to a water leg inlet  84  of the water leg  16 . 
       FIG. 8  shows via arrows the flow path of water entering a prior art water leg  16 P wherein the water flows into the interior  96 P of an innermost pipe  86 P of two concentric pipes  86 P and  88 P provided in the prior art water leg  16 P. The water then flows up within the innermost pipe  86 P and flows over the top of the innermost pipe  86 P. The water then enters an annulus  92 P located between the two concentric pipes  86 P and  88 P before flowing downward within the annulus  92 P to a water leg water outlet  98 P. The water leg water outlet  98 P of the prior art water leg  16 P is in fluid communication with the annulus  92 P and serves to remove water from the prior art water leg  16 P. 
     In prior art water legs  16 P, the water leg inlet  84 P to the water leg  16 P was a bottleneck that restricted flow and caused undesirable pressure drop through water outlet piping  90 P and the water leg  16 P due to the restricting flow area within the innermost pipe  86 P. 
       FIG. 9  shows the water leg  16  employed in the present invention. In the present water leg  16 , the water outlet  82  from the vessel  12  is connected to the water leg inlet  84  of the water leg  16 , and the water leg inlet  84  of the water leg  16  communicates with an annulus  92  between the two concentric pipes  86  and  88  provided in the present water leg  16 . Thus, upon entering the present water leg  16 , the water flows upward within the annulus  92  between the pipes  86  and  88  until it reaches the top  94  of the innermost pipe  86  which serves as a weir for the water to flow over and into the interior  96  of the innermost pipe  86  from which it falls downward within the interior  96  of innermost pipe and then exits the present water leg  16  at the water leg water outlet  98  that is in communication with the interior  96  of the innermost pipe  86 . 
     Referring to  FIG. 10 , to increase or decrease the functional height of the innermost pipe  86 , the present water leg  16  is provided with an external adjuster  100 . The external adjuster  100  is comprised of an internal slip-sleeve  102  which rides up and down on an internal smooth pipe section  104  and external means for raising and lowering the slip-sleeve  106 . The slip sleeve  102  is sealed with O-rings  108  onto the smooth pipe section  104  to avoid leakage which would defeat its function. The slip sleeve  102  is connected via a vertical pipe extension  116  to an external jack screw assembly  106  as a means for raising and lowering the slip-sleeve  106  relative to the lower portion of the innermost pipe  86 . The external jack screw assembly  106  is provided with a worm gear mechanism  112  that is mated to a hand wheel  114  so that turning the hand wheel  114  clockwise raises the slip sleeve  102 , while turning the hand wheel  114  counterclockwise lowers the slip sleeve  102 . The worm gear mechanism  112  connects to the slip sleeve  106  via the vertical pipe extension  116  which is preferably a hollow, light-weight rod which is lubricated through a packing gland  118  to completely seal the water leg  16  so no contaminants including, but not limited to water, oil or gas, escape into the atmosphere. 
     As shown in  FIG. 9 , the water inside the water leg  16  rises between the two concentric pipes  86  and  88 , and spills over into the inner pipe  86  at the elevation set by the adjuster  100 . A water leg gas equalizer line  120  connects the top  122  of the water leg  16  with a gas layer  124  located above a gas-oil interface  126  within the top  22  of the vessel  12  to equalize pressure between the two structures  12  and  16 . 
     While the invention has been described with a certain degree of particularity, it is manifest that many changes may be made in the details of construction and the arrangement of components without departing from the spirit and scope of this disclosure. It is understood that the invention is not limited to the embodiments set forth herein for the purposes of exemplification, but is to be limited only by the scope of the attached claim or claims, including the full range of equivalency to which each element thereof is entitled.

Technology Classification (CPC): 1