Abstract:
In a method of crude oil production where at a well head a mixture of particulates, crude oil and water is produced for storing in a production tank for settlement of the mixture in to the constituent parts for separate extraction from the tank or the mixture is pumped though a pipeline to a remote location, the mixture is transferred from the well head to the production tank or to the pipeline through a transfer duct in which an initial separation of the mixture is caused by heating material in the duct by a surrounding jacket and by running an auger flight with a ribbon flight in the duct which carries the particulate materials along the duct for discharge.

Description:
[0001]     This invention relates to a method for the treatment of crude oil from a well. The arrangement as described hereinafter provides a mechanical pre-heating system for production crude between the wellhead and the production tank or a system providing crude oil processing prior to pipe line transportation.  
       BACKGROUND OF THE INVENTION  
       [0002]     Heavy crude oil produced from a well contains the crude oil which is generally highly viscous due to its low temperature, water and particulates of sand. It is necessary to separate out these materials and for this purpose the production material from the well is often pumped into a tank, which is in many cases located adjacent the well head, where the materials are allowed to settle so that the particulates deposit in a layer at the bottom of the tank and above the particulates collects a layer of the water and above the water collects the crude oil. In order to accelerate the settlement, bearing in mind the high viscosity of the crude oil, heat is generally applied to the production tank so as to raise the temperature of the materials within the tank to a predetermined temperature lower than the boiling point of the water. This heating is effected by a pipe inserted into the tank into which heat is injected. One example of a heating system is shown in published PCT application WO 02/084195 of Lange published Oct. 24, 2002, the disclosure of which is co-incorporated herein by reference.  
         [0003]     For safety reasons it is required that the production tank is located 75 feet away from the well head so that a line extends horizontally from the well head to the tank and introduces the mixed materials from the well head into the tank at a position at a height on the wall on the tank. The pressure from the well therefore must also supply the necessary pressure for forcing the viscous materials through the pipe from the well head to the tank.  
         [0004]     In some cases processing chemicals are injected into the pipe at or adjacent the well head so as to be mixed in with the production materials as they are transferred along the pipe to the production tank.  
         [0005]     In other cases the product is transported from the well head to a transfer pipe line which transfers it to a remote location for collection and/or treatment. Thus the product is merely collected and pumped through the pipe over a limited distance to a remote location. The pipe line can be of small diameter such as two inches for transfer over a limited distance of up to two miles.  
         [0006]     The following problems are commonly encountered by heavy oil producers using the above technology today: 
        1. High flow line pressure from the wellhead to the production tank or transfer pipe caused by the heavy cold production fluids.     2. Increased flow line pressure which reduces oil production and efficiency of the down hole pump.     3. Adequate heat from wellhead to storage tank for (gas and oil flows) is not available other than wellhead engine glycol or exhaust, if there is a wellhead engine.     4. The cooling effect that the required 75 feet of exposed flow line has on the production crude, insulated or not, especially in winter.     5. The convection currents created in the production tanks to current hard firing immersion tube heaters due to the large temperature changes which are necessary from the inlet temperature to the processing temperature. These convection currents impact the ability of solids to settle and to achieve clean oil.     6. The ineffective introduction of treatment chemicals into the flow line. The crude is cold. foamy and solids laden. The current flow line offers no method of chemical distribution in product and no method of de-sanding or ensuring full flow capability.        
 
       SUMMARY OF THE INVENTION  
       [0013]     It is one object of the present invention therefore to provide an improved method of treating crude oil.  
         [0014]     According to one aspect of the invention there is provided a method of crude oil production comprising: 
        producing at a well head a mixture of particulates, crude oil and water;     storing the mixture in a production tank for settlement of the mixture in to the constituent parts for separate extraction from the tank;     transferring the mixture from the well head to the production tank through a transfer duct;     and while transferring the mixture, commencing an initial separation of the mixture.        
 
         [0019]     Preferably heat is applied to the mixture as it is transferred.  
         [0020]     Preferably the heat is applied by a jacket surrounding a pipe through which the material passes.  
         [0021]     Preferably the pipe is of increased diameter to increase dwell time.  
         [0022]     Preferably the pipe is at least 12 inches in diameter.  
         [0023]     Preferably the pipe contains an auger flight.  
         [0024]     Preferably the auger flight is rotated in a direction to move the particulate materials in a direction toward the tank so as to move the particulate materials to a discharge at or within the tank.  
         [0025]     Preferably the auger flight has a variable pitch.  
         [0026]     Preferably the auger flight has at least a section with a ribbon flight.  
         [0027]     Preferably the transfer duct is divided into at least two paths at its end at the tank for feeding a lighter section including the crude oil through an upper path and a heavier section including the water through a lower path.  
         [0028]     Preferably the upper path includes a heat exchanger for receiving heat from the stack gases of the heater.  
         [0029]     Preferably the transfer duct includes a gas vent which is located at the tank so that gases are released from the stream above the liquid level to avoid discharging bubbles into the liquid which can cause circulating currents which can interfere with the settlement within the production tank.  
         [0030]     According to a second aspect of the invention there is provided a method of crude oil production comprising: 
        producing at a well head a mixture of particulates, crude oil and water;     storing the mixture in a production tank for settlement of the mixture in to the constituent parts for separate extraction from the tank;     transferring the mixture from the well head to the production tank through a transfer duct;     and while transferring the mixture in the duct, heating the mixture.        
 
         [0035]     Preferably heat is applied to the mixture in the duct sufficiently to avoid the requirement for heating in the tank.  
         [0036]     Preferably material from the tank is circulated through the duct and back to the tank to avoid the requirement for heating in the tank.  
         [0037]     According to a third aspect of the invention there is provided a method of crude oil production comprising: 
        providing a mixture of particulates, crude oil and water;     transferring the mixture through a transfer duct;     while transferring the mixture in the duct, heating the mixture;     and providing an auger flight in the duct operable to carry the particulate materials to one end of the duct for discharge, while the crude oil and water flow along the duct.        
 
         [0042]     In one arrangement, the transfer duct transfers the mixture to a pump and a pipe line for transferring the mixture to a remote location.  
         [0043]     In this arrangement preferably the particulate material is discharged from the transfer duct prior to the pump.  
         [0044]     In this arrangement preferably the auger flight is arranged to form a plug of the particulate material, a part of which is periodically released by a valve  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0045]     Embodiments of the invention will now be described in conjunction with the accompanying drawings, in which:  
         [0046]      FIG. 1  is a schematic view of a well head crude oil production system according to the present invention.  
         [0047]      FIG. 2  is a side elevational view of a well head crude oil production system of  FIG. 1 .  
         [0048]      FIG. 3  is an end elevational view of the embodiment of  FIG. 1 .  
         [0049]      FIG. 4  is a side elevational view of the production system according to the present invention.  
         [0050]      FIG. 5  is a top plan view of the production system according to the present invention. 
     
    
       [0051]     In the drawings like characters of reference indicate corresponding parts in the different figures.  
       DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0052]     In  FIG. 1  is shown schematically an oil production system including a well  10  which provides oil production at a well head  11  for supply through a pipe  12  to a production tank  13 . The tank is arranged to receive the materials in which settling occurs to provide a layer of particulate material at the base of the tank, a layer of water on top of the sand and the required oil in a layer at the top of the tank.  
         [0053]     The conventional system is modified by the addition of an initial production treating system generally indicated at  20  which includes a duct  21  containing an auger flight  22  and surrounded by a jacket  23 . Steam is supplied to the jacket  23  by a heating system  24  so that the steam condenses in the jacket generated a liquid which runs back along the bottom of the jacket to an outlet port  25  from which the liquid runs back to the heating system  24 . The jacket surrounds substantially the whole of the duct and the duct extends substantially the whole of the distance from the well head  11  to the tank  13 .  
         [0054]     The auger flight  22  is driven by a motor  26  on the well head end of the duct  21 . A temperature sensor  27  detects the temperature of the materials within the duct at the tank  13  so as to control the heat supply from the heating system  24  to maintain a required temperature as a material to enter the tank.  
         [0055]     The motor  26  drives the auger flight in a direction so that the flight tends to carry particulate materials within the bottom of the duct toward the tank end. The end of the duct within the tank includes a discharge mouth  33  which is arranged within the tank so that the discharged materials can rise centrally within the tank if lighter or can fall downwardly within the tank, primarily the particulate materials, the heavier materials falling into a collection system  34  arranged centrally of the tank for collecting and discharging the materials as a primary discharge system. (See  FIGS. 4 and 5 )  
         [0056]     The auger flight has a ribbon flight section  22 C at least in the area closest to the tank so as to allow the liquids to flow through the centre of the ribbon flight section with less turbulence providing a smoother flow of the liquids after the particulate materials have been primarily extracted for transport to the plug. The ribbon flight may extend along the complete length of the auger which is along the complete length of the heated duct so as to allow the fluid to flow in the center and the particulates to be carried along the bottom of the duct to the tank.  
         [0057]     The outlet mouth of the duct may be located at the tank wall rather than in the centre as shown in  FIG. 1 .  
         [0058]     In  FIG. 2  is shown an arrangement in which the lighter materials rise through a secondary inlet duct portion  40  so that the lighter materials, primarily the oil can be raised through the duct  40  to a mouth  41  injecting into the tank  13  at a position above the expected water level. The heavier materials in the duct transfer through the mouth  33  at the side wall into the tank primarily below the water level. The liquid rising in the duct  40  can be heated by a heat exchanger  42  from the flue pipe of the heating system  24 .  
         [0059]     Also in  FIG. 2  is shown a vent duct  50  which allows gases in the stream to be released from the stream above the liquid level to avoid discharging bubbles into the liquid which can cause circulating currents which can interfere with the settlement within the production tank. The heat in the transfer duct  20  can be as much as 140 degrees C. so that water can be converted to steam which would generate bubbles in the tank if released into the tank. The vent  50  may discharge into the tank or may discharge to atmosphere.  
         [0060]     An additional return line can be provided from the well head end of the duct to the tank so as to use the system in reverse flow arrangement for heating of liquid within the tank by passing the materials through the duct in the reverse direction and then returning the materials to the tank through the return duct. This allows the tank to avoid the necessity for a specific heating system within the tank since the majority of the tank can be initially heated using the circulation system and then when the production is started, the heat from the duct is sufficient to maintain the materials within the tank at the required separation temperature. This avoids the generation of convection currents within the tank and maximises the settling action. In  FIG. 3  is shown a end elevational view of the system including the heater  24  including a burner  24 A and heat exchange tubes  24 B. The flue  24 C can be allowed to merely discharge the gases or can be connected to the heat exchanger  42  shown in  FIG. 2 . The steam from the heat exchange tube  24 B is communicated through a duct  24 D to the inlet of the jacket  23 . The return from the jacket returns the liquid to the heater  24 . The duct is mounted on one or more support legs  50  and arranged so that it is generally horizontal but with a slight inclination so as to run the return liquid back toward the outlet for the heater.  
         [0061]     There has been very little work done on technology involving the atmospheric treating of petroleum products in recent years. It is believed that by incorporating a number of certain advancements in recent technology developed by the present Assignee, a significant step forward will be made.  
         [0062]     In particular, the utilization of: 
        1. Auger tank de-sanding, as is known and provided by the present Assignee.     2. Two phase thermo siphon tank heating as shown in the Lange patent application mentioned herein before.     3. And a combination of both between the flow line and storage tank will create a low cost, very effective mini or micro treating system that simply does not exist today.        
 
         [0066]     The components can be made any length, diameter or material make up that is required to achieve the desired temperature rise or fall, (this system may also be a cooler).  
         [0067]     The heating system disclosed in the above PCT application of Lange has a condenser portion which may be the jacketed are however it may also include the auger shaft as well as the flighting section if rotating mechanical seals and double wall auger flighting were incorporated. The heating system may utilize a condenser of standard design in the production tank (controlled by flow valves) the greatest amount of heat however will go to the heating of the duct  20 .  
         [0068]     The following features may be considered in the flighting designs: 
        1. The auger design may incorporate multi purpose capability.     2. Simple helical flights of standard design can be used for low cost solutions.     3. Variable pitch screw of same outside diameter to allow for velocity drop after temperature is up and chemical is mixed.     4. Paddles or weirs in the auger tube can be used to enhance mixing and heat distribution into petroleum products.     5. Perforations, slots, holes in the flight, or other flighting modifications either whole or in part of the auger, can be used to both promote mixing, heating, shearing and subsequent separating of H20, crude and solids.     6. An unimpeded fluid flow can be created by use of a ribbon auger flight in last stages of the auger. The ribbon outer lead edge of the flight still allows for solids distribution into production tanks.        
 
         [0075]     In one mode of operation the system is used in unidirectional operation where in a first method of operation, the system is installed on typical production well with tank located 75 feet from the wellhead. The storage tank access port is a standard 10″ full opening knife gate valve either retro-fit by hot tap installation or standard install when tank is empty, as is well known to one skilled in the art.  
         [0076]     The valve is installed inline with wellhead, approximately 5 feet above tank floor. On a retrofit the existing crude flow line is cut, threaded and with a flex coupling and valve tied into the flow line inlet on the system. The original flow line is tied into the other side of the tee with a valve.  
         [0077]     The production fluid follows the helical path defined by the flight taking advantage of retention time and velocity drop through the larger diameter flow line.  
         [0078]     The internal screw, through a packing gland, is driven by hydraulic return pressure or electric over gear drive.  
         [0079]     The auger drive incorporates centralized and thrust components along with secondary centralisers, throughout the length of the screw to maintain the shaft central within the duct. The auger is driven to rotate either continuously, or intermittently from 0 to higher RPM, generally approximately 5 RPM.  
         [0080]     The heating system is well known to one skilled in the art. A small 9-burner unit can be affixed directly onto the transfer duct or alternatively have hoses and valves to control temperature to the tank condenser.  
         [0081]     The transfer duct may have flat irons affixed to direct steam away in the upper half of the tube and return in the lower half. The transfer duct will be slightly sloped toward the return outlet so the jacket will quickly return condensate liquid to the heating system.  
         [0082]     In a second method of operation, in a case where the tank is cold the auger may be rotated in reverse to bring cold crude into the MPT for heating. The previous inlet to the NVT is now the exit with the crude being recycled into the production tank.  
         [0083]     Chemical may be injected to batch treat slop or hard to treat crude in this manner. Temperature rise could be achieved by counter rotation, and then once temperature rise was achieved, the auger would be rotated to the treating mode. The use of the auger flight improves chemical mixing.  
         [0084]     In an alternative arrangement (not shown) where the duct  20  transports the production from the well to a pump. At the pump is provided a discharge valve which is periodically operable to discharge the particulate materials into a collection system for discard.  
         [0085]     The auger flight is arranged so that it increases the quantity of particulate material at the discharge end adjacent the valve so as to form in effect a plug of the particulate material blocking the duct at that area. Thus when the valve is opened a portion of the plug can be discharged without the plug being broken up or wholly discharged so that the plug prevents the escape of the liquid materials within the duct while allowing the plug itself to be partially discharged. The valve can be operated periodically by a pressure sensor which detects the pressure in the plug due to the packing of the plug with additional particulate materials as the materials are fed by the auger flight. The oil from the duct  20  is to the pump is removed from the duct  20  at an outlet point downstream of the plug.  
         [0086]     Since various modifications can be made in our 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 scope, it is intended that all matter contained in the accompanying specification shall be interpreted as illustrative only and not in a limiting sense.