Abstract:
A treater for electrostatically and/or mechanically separating emulsified brine from oil during longitudinal flow through a horizontally elongate metal tank. Emulsion is directed through a louver stack made up of a large number of inclined parallel plates. The openings on the upstream end and on the downstream end of this louver stack are adjustable from outside of the metal tank, so as to allow the operator to adjust the flow rate through the treater as operating parameters change.

Description:
FIELD OF THE INVENTION 
     This invention relates generally to oil/water emulsion treating methods and apparatuses, and, more particularly, to oil/water emulsion treating methods and apparatuses employing an elongate horizontal separation vessel. 
     BACKGROUND OF THE INVENTION 
     Petroleum as it is naturally produced from an underground formation, is in most cases a mechanical mixture of oil, entrained gas and salt water, some of which latter may be present as an oil/brine emulsion. It is desirable, and usually necessary to treat the petroleum thus produced at the wellhead, for the separation and removal of the entrained gas and emulsified brine, in order to render the oil pipelineable. Usually, the separated salt water is pumped back into the formation, in order to assist in maintaining the pressure therein, and also to resolve the salt water disposal problem. Separated gas is vented or flared, if in small quantities, and if in commercial volumes, is delivered to a pipeline for distribution. The equipment used for this three-phase separation is known as a treater, and is generally quite familiar to those to whom the present invention will be addressed. 
     Such treaters normally involve the heating of the produced petroleum, in order to lower the viscosity of the fluid phase, and also to assist in the separation of the entrained gas. Brine droplets are coalesced either mechanically, as by forcing the emulsion through a series of perforated baffles; or electrostatically as by forcing the emulsion through a high-energy, electrically charged field; or chemically, by means of surface-active chemical agents which reduce the surface tension on the water droplets, thereby allowing them to coalesce into larger drops for separation by gravity. Frequently, two or more coalescing methods are employed in a treater. 
     Treaters have evolved in design from early developed open vats which maintained the produced petroleum in stationary condition for several days, permitting the entrained gas to freely separate to atmosphere and the salt water to separate to the bottom of the vat by gravity. There evolved heating methods in order to expedite the treatment by reducing the viscosity of the oil, as described. Subsequent development evolved the heater-treater which is the current state-of-the art comprising an elongated enclosed tank having a burner-fired heater section and a downstream treater section for a continuous flow, with a series of perforated baffles positioned within the treater section transversely to the flow of fluids; the perforated baffles function to promote the even distribution over the full cross-sectional area of the treater section of the fluids in motion, and to cause a pressure drop within the fluid across the perforated baffles which results in a release of entrained gases, which then collect in the upper volume of the tank for removal. However, salt water emulsions within the oil have continued to be inefficiently treated by gravity settling and baffling of the flow following heating: thus, further measures have been necessary in order to cause coalescing of the small droplets of brine into larger drops which could be settled out by gravity. 
     The conventional treatment has the operational disadvantages of being time-consuming, due to the residence-time required in the treater and the requirement that the petroleum be heated to a sufficiently high temperature to reduce the viscosity thereof so that coalescing of the emulsified droplets will be encouraged. The maintenance of a large quantity of oil at a relatively high temperature is costly of energy, and requires the equipment involved to be capable of sustained operation at the temperatures involved. 
     Treaters in current use are normally tanks in the form of elongated horizontal cylinders divided by means of internal partitions into compartments through which the petroleum will sequentially flow. Burner-fired heaters are normally included in the upstream heater section for heating the emulsion to the desired temperature, during which most of the entrained gas and some of the brine will separate from the emulsion. The partially demulsified brine then flows into a treater section, in substantially gas-free state, encountering a series of baffles adapted to encourage even flow of fluids and to avoid the formation of flow channels within the fluid body, thereby to assist in separation of remaining gases and coalescing of water droplets, and their separation by gravity to the bottom of the tank for ultimate discharge removal. 
     Various techniques of improvement have heretofore been employed in order to minimize treatment time and heat energy consumption. In my U.S. Pat. No. 4,329,159, “Energy Saving Heavy Crude Oil Emulsion Treating Method and Apparatus for Use Therewith” (which is incorporated herein in its entirety by this reference), there is described a method and apparatus of the type described, additionally including a number of metallic apertured grid electrodes suspended adjacent apertured baffles, the electrodes being supplied with electrical energy. A series of longitudinally spaced electrical fields of high potential are thereby created, which cause droplets of emulsified brine to move in violent random fashion, the droplets coalescing and collecting into drops of sufficient weight as to fall by gravity to the lower portion of the treater section for removal. 
     In my U.S. Pat. No. 4,919,777, “Electrostatic/Mechanical Emulsion Treating Method and Apparatus” (which is incorporated herein in its entirety by this reference), there is described an improved method and apparatus of this type, wherein, immediately downstream of the apertured grid electrodes, the flow is directed downwardly through a plurality of inclined open-ended tubes arranged in bundle-fashion. 
     Unfortunately, most such prior art methods and the apparatuses are inherently inflexible in operation. The apparatuses are designed for a narrow range of operating parameters, such as flow rate, oil/water ratio, salinity, temperature, viscosity, etc. After the apparatuses are manufactured and installed, they are only effective when operating within these narrow design operating ranges. When operating conditions change, an entirely new apparatus must be designed, built and installed. This is a special problem for crude oil producers, because crude oil/water emulsions produced in an oil field can vary dramatically from well to well, and even within the same well from day to day. 
     Accordingly, there is a need for further improvements in methodology and apparatuses which will overcome these problems in the prior art. 
     SUMMARY 
     The invention satisfies this need. The invention is an emulsion separating treater comprising: (a) a generally horizontally elongate enclosed tank having a longitudinal axis, a first end and an opposed second end, (b) an emulsion inlet port, (c) an oil outlet port and a water outlet port, (d) a louver stack located within the tank between the oil inlet port and the oil outlet port, the louver stack being disposed perpendicular to the longitudinal axis of the tank and comprising a plurality of at least four parallel plates each having an upstream edge and a downstream edge, adjoining upstream edges defining a plurality of generally horizontal inlet openings and adjoining downstream edges defining a plurality of generally horizontal outlet openings, and (e) an adjustment mechanism for adjusting the opening widths from outside of the tank. 
    
    
     DRAWINGS 
     These features, aspects and advantages of the present invention will become better understood with regard to the following description, appended claims and accompanying figures where: 
     FIG. 1 is a perspective view of the preferred embodiment apparatus of the invention, with a longitudinal portion thereof cut away to illustrate the interior of the apparatus; 
     FIG. 2 is an end view of the apparatus of FIG. 1 depicting the heater section; 
     FIG. 3 is a top plan view of the apparatus of FIG. 1 with a portion cut away to illustrate the position of the several components and the location of certain outlets; 
     FIG. 4 is a longitudinal cross-sectional view of the apparatus of FIG. 1; 
     FIG. 5 is an isometric detail view of a louver stack useful in the invention; 
     FIG. 6 is a diagrammatic side view of a louver stack useful in the invention; and 
     FIG. 7 is a diagrammatic front view of a louver stack useful in the invention. 
    
    
     DETAILED DESCRIPTION 
     The following discussion describes in detail one embodiment of the invention and several variations of that embodiment. This discussion should not be construed, however, as limiting the invention to those particular embodiments. Practitioners skilled in the art will recognize numerous other embodiments as well. 
     The invention is an emulsion separating treater  10  useful for separating water droplets from an oil/water emulsion. The treater  10  comprises an elongate horizontal tank  12  having disposed therein one or more louver stacks described in greater detail below. 
     The tank  12  is a fully enclosed vessel, typically made from a steel. The tank is elongate and generally disposed in the horizontal. The tank has a first end  16 , an opposed second end  18  and a longitudinal axis  20 . 
     In the embodiment illustrated in the drawings, a two-stage heater section  22  is disposed proximate to the first end  16  of the tank  12  and a treater section  24  is disposed proximate to the second end  18  of the tank  12 . A transverse bulkhead  26  separates the tank  12  into these two functional sections  22  and  24 . A longitudinal bulkhead  28  extends from the first end  16  of the tank  12  to the transverse bulkhead  26  thereby defining a first longitudinally extending heater compartment  30  and a second longitudinally-extending heater compartment  32 , situated side-by-side and connected in series. The longitudinal bulkhead  28  has an upper opening  54  and a lower opening  56 , both located adjacent the first end  16  of the tank  12 . 
     Within the two heater compartments  30  and  32  are substantially identical first and second heaters  34  and  36 , respectively. Each heater  34  and  36  has a tubular lower leg  38 , a tubular upper leg  40  and a U-shaped end connector  42 . The lower leg  38  of each heater  34  and  36  extends through the first end  16  of the tank  12 . The upper leg  30  of each heater  34  and  36  is connected in fluid tight communication to a stack  44  which extends upwardly outside of the tank  12 . The temperature of the emulsion is monitored and controlled in the first heater section  34  by a first temperature sensor/controller  46  and in the second heater compartment  32  by a second temperature sensor/controller  48 . 
     The tank  12  comprises an emulsion inlet port  50  through which emulsion can be delivered continuously into the heater section  22 . The emulsion inlet port  50  desirably has a normally-open manually operated inlet valve  52  associated therewith. 
     In the embodiment illustrated in the drawings, the transverse bulkhead  26  is divided by the longitudinal bulkhead  28  into a left half  58  and a right half  60 . The left half  58  is solid, while the right half  60  has a lower opening  62 , an upper opening  64  and an intermediate opening  66  defined therein. 
     Disposed within the treater section  24  is at least one louver stack  68  disposed perpendicular to the longitudinal axis  20  of the tank  12 . The louver stack  68  comprises a plurality of at least four parallel plates  70 . Each parallel plate  70  has an upstream edge  72  and a downstream edge  74 . The distance between the upstream edge  72  and the downstream edge  74  of each plate  70  (i.e., the width of each plate  70 ) is between about 6 inches and about 36 inches, typically between about 16 inches and about 20 inches. Adjoining upstream edges  72  of the parallel plates  70  define a plurality of generally horizontal inlet louver openings  76  through which an oil/water emulsion flowing through the tank  12  must pass. Similarly, adjoining downstream edges  74  of the parallel plates  70  define a plurality of generally horizontal outlet louver openings  78  from which emulsion passing through the louver stack  68  must exit the louver stack  68 . Each of the plates  70  is inclined downwardly so that each inlet louver opening  76  is at an elevation slightly higher than its corresponding outlet louver opening  78 . By this design, emulsion flowing into each inlet louver opening  76  is diverted downwardly as it passes through the louver stack  68 . 
     Typically, the louver plates  70  are made from a metal, such as a steel. The louver openings  76  and  78  are typically 0.25 inches to 1.75 inches when maximized. The number of plates  70  in each louver stack  68  will depend upon the diameter of the tank  12 . For a 6 foot diameter tank, the typical number of plates  70  in each louver stack  68  is 70-80. In a 12 foot diameter tank  12 , the typical number of plates  70  in each louver stack  68  is 125-150. 
     Some or all of the parallel plates  70  within the louver stack  68  are movable with respect to adjacent plates  70  so that the width of at least some of the louver openings  76  and  78  are adjustable from outside the tank  12 . This can be accomplished in many different ways. In the embodiments illustrated in FIGS. 6-7, this is accomplished by making each of the plates  70  pivotable about horizontal axes  80  disposed between the upstream edge  72  and the downstream edge  74  of each plate  70 . As best seen in FIG. 6, to narrow the flow path through the louver stack  68 , every other plate  70  is pivoted clockwise, while the remaining plates  70  are pivoted counterclockwise. By this action, half of the inlet louver openings  76  and half of the outlet louver opening  78  are narrowed. 
     FIG. 7 illustrates a push/pull rod mechanism  82  for adjusting the louver opening widths from outside the tank  12 . In FIG. 7, a push/pull rod  84  is movable in a left/right direction. The distal end  86  of the push/pull rod  84  is attached to a rocker arm  88  which pivots about a pivot axis  90 . The rocker arm  88  has a control arm  92  and a pair of oppositely disposed operation arms. In the drawings, these operation arms are designated as first operation arm  94  and second operation arm  96 . At the distal end  98  of the first operation arm  94 , a first connecting rod  100  extends upwardly and attaches to the downstream edges  74  of alternating plates  70  in the louver stack  68 . At the distal end  102  of the second operation arm  96 , a second connecting rod  104  extends upwardly and attaches to the downstream edges  74  of the remaining plates  70  in the louver stack  68 . Thus, when the push/pull rod  84  is slid to the right in FIG. 7, the rocker arm  88  is rotated in a counterclockwise direction, thereby pushing the second connecting rod  104  upward and pulling the first connecting rod  100  downward. By this operation, the first and second connecting rods  100  and  104  draw alternating adjacent pairs of the upstream edges  72  and the downstream edges  74  of the plates  70  closer together, thereby causing the widths of one half of the louver openings  76  and  78  to narrow. To re-widen the widths of the louver openings  76  and  78 , the push/pull rod  84  is slid back to the left, towards the original orientation illustrated in FIG.  7 . Alternatively, a similar push/pull rod mechanism  82  can be attached to the upstream edge  72  of each plate  70 . In such a design, the operation of the push/pull rod mechanism  82  would be the same as described above, except it would operate in reverse. 
     In a typical embodiment of the invention  10 , the louver openings  76  and  78  are adjustable by at least 0.5 inches. Preferably, the louver openings  76  and  78  are continually adjustable from a full open position to a fully closed position. 
     Typically, the apparatus  10  will comprise a plurality of spaced apart louver stacks  68  which define a plurality of discrete demulsifying units  108  disposed in series within the treater section  24 . The embodiment illustrated in FIGS. 1-4 has five demulsifying units  108 . The treater  10  may contain any desired number of demulsifying units  108  and such specific configurations will normally be determined by the characteristics of the emulsion to be treated. 
     Preferably, an electrostatic field inducer  110 , such as an electrostatic grid, is transversely disposed in vertical alignment immediately upstream of each louver stack  68 . The electrostatic field inducers  110  are supported from the tank  12  by conventional electrical insulating means (not shown). An electrical current-supplying transformer (not shown) supplies high voltage to the electrostatic field inducers  110 . The electrostatic field inducers  110  impart an electrostatic charge to the water component of the emulsion as it passes through the electrostatic field inducers. Such electrostatic charge facilitates the separation of water from oil in the emulsion as the emulsion passes through the grounded louver stack  68 . 
     Proximate to the second end  18  of the tank  12 , an angularly disposed baffle  112  extends inwardly into tank  12  and is connected at its inner edge to a vertical transverse baffle  114  having an upper horizontal edge. The upper horizontal edge of the transverse baffle  114  acts as an oil weir  116  and determines the depth of the emulsion throughout the apparatus  10 . Baffles  112  and  114 , together with the interior surface of tank  12  adjacent the second end  18  of the tank  12 , cooperate to define a reservoir  118  into which substantially brine-free oil is discharged. 
     The transverse baffle  114  serves a three-fold purpose: first, it automatically maintains the liquid level within the sections  22  and  24  at a desired depth; second, it prevents commingling of brine and gas-free oil within the reservoir  118  with the emulsion being treated in the treater section  24 ; and third, it allows gas and brine-free oil to be withdrawn from the reservoir  118  without affecting the liquid level of emulsion in the heater section  22  and in the treater section  24 . 
     The second end  18  of the tank  12  also has a gas outlet  120 , a brine-free oil outlet  122  and a brine outlet pipe  124  positioned therein. The gas outlet  120  extends by its vertical standpipe  126  into a gas zone  128  in the upper portion of the tank  12 . The brine outlet pipe  124  extends into the lower interior of the tank  12  and is ported for ingress of the brine for continuous discharge to exterior brine removal facilities (not shown). 
     A number of inverted, longitudinally-spaced boxes  130  extend longitudinally along the interior bottom portion of tank  12 . The boxes  130  have openings  132  in the sides thereof through which sand and silt (not shown) may flow to the interior thereof. The interior of each box  130  is connected to a first slurry conduit  134  that extends outwardly through the tank  12  to a valve  136 . Second slurry conduits  138  are connected to each valve  136  and extend to a header  140  adapted to carry settled particulate solids as a slurry when the valves  136  are opened to pressures substantially lower than that within the tank  12 . This permits the accumulated sand (with some brine) to be flushed to a disposal site. 
     In operation, the first and second heaters  34  and  36  supply heat to the heater compartments  32  and  34  at the first end  16  of the tank  12 . An oil/water emulsion sequentially flows into the tank  12 , via the emulsion inlet port  50 , through the two heater compartments  32  and  34  and thence into the treater section  24 . The horizontal flow is at a relatively slow flow rate on the order of one-quarter foot to one foot per minute. 
     The heat supplied by the first heater  34  as the emulsion flows along the upper leg  40  of the first heater  34  is typically only that necessary to lower the viscosity of the emulsion to the extent free gas and free brine separate therefrom. Free gas escapes from the emulsion at this point and the density of the emulsion decreases. The emulsion then flows downwardly and then longitudinally within the first heater  34  towards the second end  18  of the tank  12 . The temperature of the emulsion is further increased due to the heating effect of the lower leg  38  of the first heater  34 , thereby freeing additional gas and brine from the emulsion. 
     The gas released in the first heater compartment  30  flows through the upper opening  54  in the longitudinal bulkhead  28  into the upper portion of the second heater compartment  32 . Water that separates from the emulsion in the first heater compartment  30  flows transversely through the lower opening  56  in the longitudinal bulkhead  28  into the second heater compartment  32 , together with the partially heated emulsion. 
     As emulsion flows through the second heater compartment  32 , it is further heated by the second heater  36 . Such further heating is typically only sufficient to lower the viscosity of the emulsion to the point where the remaining dissolved gas is separated from the emulsion. The temperature in the second heater compartment  32  also lowers the viscosity of the emulsion to the extent that a portion of the emulsified brine separates from the emulsion. The separated emulsified brine coalesces into droplets that flow by gravity downwardly to the bottom portion of the second heater compartment  32  and merge with the brine that has flowed to the lower portion of the second heater compartment  32  from the first heater compartment  30 . 
     Emulsion that is substantially free of gas but still contains a substantial quantity of emulsified brine next flows through the intermediate opening  66  in the transverse bulkhead  26  into the treater section  24 . Gas flows from the second heater compartment  32  into the upper portion of the treater section  24  through the upper opening  64  in the transverse bulkhead  26 . Brine that is collected in the lower portion of the heater section  22  flows through the lower opening  62  in the transverse bulkhead  26  into the lower portion of the treater section  24 . It will be appreciated that the flow of gas, brine and emulsion is substantially horizontal, thereby offering low resistance to the rise of gas bubbles and the falling of brine droplets. 
     In the treater section  24 , the emulsion flows to the region of the first demulsifying unit  108 . Here, the emulsion passes through the first electrostatic grid  110 , where the brine droplets are subject to high potential electrostatic fields surrounding the electrodes, and take on an electrostatic charge therefrom. When so charged, these droplets rapidly move about repelling, attracting and colliding with one another, in energetic action since all droplets receive a charge, regardless of size. Droplets collide with sufficient energy to overcome the emulsifying forces, and combine into larger drops. 
     Immediately downstream of the first electrostatic grid  110 , movement of the emulsion progresses to the first louver stack  68 . The emulsion enters the first louver stack  68  through the inlet louver opening  76 . Within the first louver stack  68 , the electrified emulsion contacts the grounded metal plates  70  and adhesion of the electrified brine droplets occurs. At the metal plates  70 , the brine droplets lose their charge and trickle downwardly towards the outlet louver openings  78  and then fall by gravity to the bottom of the tank  12 . Also, the deposition of minute brine particles upon the plate  70  causes other droplets to coalesce therewith, thus producing minor streams which trickle downwardly by gravity to the bottom of the tank  12 . 
     The emulsion then continues downstream through successive demulsifying units  108 . In each successive demulsifying unit  108 , more and more of the brine within the emulsion is removed. 
     As brine is removed from the emulsion, the resulting demulsified oil is of lesser density than the emulsion and rises to the top of the emulsion for accumulation as an upper strata of oil. The upper strata of oil is free of gas and brine. As the emulsion continues to be supplied to the heater section  22 , the liquid level rises in the treater section  24 , causing the oil, free of gas and brine, to flow over the weir  116  into the reservoir  118  from which it may be either intermittently or continuously withdrawn without disturbing the liquid level of the emulsion being treated in the treater section  24 . 
     The apparatus  10  maintains a gas-emulsion interface in the treater section  24  and a water-emulsion interface at a predetermined level in the lower portion of the treater section  24 , thereby facilitating uniform operation of the treater  10  for continuous feed conditions. 
     The invention provides the operator with the ability to slow down the flow rate (or, conversely, speed up the flow rate) to maximize the efficiency of the apparatus  10  depending upon changes in the characteristics of the emulsion feed stream. The operator can easily manipulate the flow rate through the apparatus  10  from outside the tank  12  by reducing or expanding the width of the louver openings  76  and  78  within the louver stacks  68 . 
     It will be understood by those familiar with the art that under certain conditions, it may be unnecessary to employ electrostatic charging of the emulsion. Moreover, it will be understood by those familiar with the art that under other certain conditions, it may be unnecessary to employ heating at the upstream end of the apparatus  10 . 
     The invention provides the operator with the ability to accommodate a wide range of A.P.I. gravities of crude oil emulsion, and provides the operator with the ability to deal with emulsions of other differing characteristics, such as differing viscosity characteristics. The invention further provides the operator with the ability to accommodate differing input rates to the apparatus, and gives the operator the ability to accommodate surging emulsion input flow rates. The invention still further gives the operator an opportunity to dislodge occasional plugging problems within the demulsifying units. The invention also provides the operator with the ability to correct miscalculations and misassumptions in the initial design of the apparatus components. 
     Having thus described the invention, it should be apparent that numerous structural modifications and adaptations may be resorted to without departing from the scope and fair meaning of the instant invention as set forth hereinabove and as described hereinbelow by the claims.