Abstract:
A pressure reducing assembly for high pressure oil wells is disclosed. The assembly includes a metallic body having inlet and outlet channels that are lined with ceramic inserts. The assembly may also include a removable pressure reducing device that is preferably formed of a ceramic material. Pipe spool pieces associated with the pressure reducing assembly transition the narrow interior flow diameter of the assembly to the larger interior flow diameter of downstream oil process piping. The spool pieces have metallic bodies, with flow channels that are lined with ceramic inserts. The ceramic inserts are disposed within the metallic spool, and are preferably designed with a flow channel taper that gradually increase the interior flow diameter from that of the outlet channel of the pressure reducing assembly to that of the process piping. The use of the ceramic inserts and liners in the pressure reducing assembly provides a method for increasing the operating life of the flow control components of high pressure oil wells.

Description:
This application is a continuation-in-part and claims the benefit of priority of U.S. patent application Ser. No. 09/451,989, filed Nov. 30, 1999 now U.S. Pat. No. 6,367,546. 
    
    
     FIELD OF THE INVENTION 
     This invention relates generally piping components for high pressure oil wells, and in particular to the use of ceramic material in wear components for a pressure reducer assembly for such wells. 
     BACKGROUND OF THE INVENTION 
     Many oil well facilities around the world operate under high pressure. In other words, the pressure within the well is sufficiently high (e.g., 3000 to 5000 psi) to carry the crude oil to the surface without pumping. Unless restricted, the crude oil flows to the surface at a high velocity and contains sand and other debris which erodes the interior surfaces of the oil well piping components. In order to limit the amount of sand and debris that is carried with the extracted oil, the high well pressure is maintained in the exit piping by using a pressure reducer at the head end of the well. For instance, a six inch inner diameter well pipe is reduced to three inches through a series of narrow channel pipe components. The flow channel is then further reduced to less than one inch, or even less than one-half inch, in the pressure reducer assembly. 
     The known pressure reducing devices are made of carbon steel and have tungsten carbide inserts to line the inside surfaces of the flow channels. The abrasive oil-and-sand mixture not only wears away the inside wall of the flow channels, but also backwashes around the outside diameter of the flow reducer and wears away the steel body of the flow reducer, resulting in gross failure of the reducer itself. Often, the metal housing surrounding the flow reducer is severely worn as well. Continuous erosion of the pressure reducer over time results in a slow and continuous loss of desired operating pressure until gross failure requires replacement. This loss in operating pressure causes an ever-increasing sand content, resulting in less efficient oil production. The average life of the known flow reducers is about 4 to 12 weeks. Oil well downtime to replace a pressure reducer and/or other components, is usually four to eight hours. High pressure oil wells typically produce about 5,000 to 12,000 barrels of oil a day. It is readily apparent that the present construction of the oil well pressure reducing assemblies leaves something to be desired with respect to wear resistance and useful life. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is a principal object of this invention to extend the operating life of high pressure oil well components, resulting in more efficient oil production. 
     Another object of this invention is to minimize abrasive wear of the steel surfaces of high pressure oil well components. 
     Another object of this invention is to minimize erosive channeling (backflow) between a pressure reducer and the reducing valve body by sealing any voids between the reducing valve and the pressure reducer. 
     Another object of this invention is to increase the wear resistance of flow channel surfaces that are susceptible to erosion wear. 
     A still further object of this invention is to minimize turbulent flow to lessen the likelihood of channeling and erosion. 
     The above and other objects are achieved in a pressure reducer made entirely of solid ceramic material, in a ceramic-lined reducing valve, and in ceramic-lined narrow bore piping components, with all ceramic elements susceptible to flow containing modified flow channel designs. The ceramic material may be any one selected from the class of technical ceramics, referring to ceramic materials exhibiting superior mechanical properties. 
     The ceramic pressure reducer lessens both the interior and exterior erosion that occurs with a steel pressure reducer. The ceramic pressure reducer is fitted into the downstream end of a ceramic-lined reducing valve. The replaceable ceramic linings of the reducing valve are more wear resistant than steel, thus protecting the interior steel surfaces of the reducing valve flow channels. The ceramic liners also provide better sealing of the area between the pressure reducer and the reducing valve channel wall. The ceramic liners in the narrow bore components, and in the reducing valve, not only wear better than steel or carbide materials, but also allow for a more precise flow channel design, thus lessening the deteriorating affects of turbulent vortex flow. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     The foregoing summary, as well as the following detailed description of a preferred embodiment of the present invention, will be better understood when read in conjunction with the drawings, in which: 
     FIG. 1 is a side elevation view of a pressure reducing assembly for a high pressure oil well; 
     FIG. 2 is a side elevation view in partial cross section showing the interior of the pressure reducing valve of FIG. 1 as viewed along line  2 — 2  thereof; 
     FIG. 3 is a cross-sectional side view of a ceramic liner used in the upstream channel of the pressure reducing valve of FIG. 2, as viewed along line  3 — 3  thereof; 
     FIG. 4 is a cross-sectional side view of an alternative embodiment of the ceramic liner shown in FIG. 3; 
     FIG. 5A is side view of a direction changing cavity liner used in the pressure reducing valve shown in FIG. 2; 
     FIG. 5B is an end view of the direction changing cavity liner shown in FIG. 5A as viewed along line  5 B— 5 B thereof; 
     FIG. 6A is a side view of a key plate liner used in the pressure reducing valve shown in FIG. 2; 
     FIG. 6B is an end view of the key plate liner shown in FIG. 6A as viewed along line  6 B— 6 B thereof; 
     FIG. 7 is a cross-sectional side view of a downstream cylindrical liner used in the pressure reducing valve of FIG. 2, as viewed along line  7 — 7  thereof; 
     FIG. 8 is a side view of a ceramic flow reducer used in the pressure reducing valve shown in FIG. 2; 
     FIG. 9 is a side view of an alternative embodiment of the ceramic flow reducer shown in FIG. 8; 
     FIG. 10 is a side elevational view in cross section showing a spool adapter assembly used in the pressure reducing assembly of FIG. 1 as viewed along line  10 — 10  thereof; 
     FIG. 11 is a side elevation view of an alternative embodiment of a pressure reducing valve according to the present invention; 
     FIG. 12 is a cross-sectional side view of a ceramic liner used in the upstream channel of the pressure reducing valve of FIG. 11, as viewed along line  12 — 12  thereof; and 
     FIG. 13 is a cross-sectional view of a downstream liner used in the pressure reducing valve of FIG. 11, as viewed along line  13 — 13  thereof. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to the drawings wherein like reference numerals indicate identical or corresponding parts among the several views and in particular to FIG. 1, there is shown a pressure reducing assembly for a high-pressure well head. For purposes of orientation, the oil flow originating from the well flows through the pressure reducing assembly according to the present invention and toward the oil process piping in the direction shown by the arrows. A pressure reducing valve  10  is connected through an isolation valve  19  to a well head manifold  25 . The downstream side of pressure reducing valve  10  is connected to a first spool adapter  20 , which is connected to a second spool adapter  30 . The second spool adapter  30  is connected to the piping that leads to the oil processing facilities (not shown). 
     Referring now to FIG. 2, the pressure reducing valve  10  has a metallic body that includes an upstream channel  11 , a direction-changing cavity  16 , a downstream channel  17 , and a key-plate recess  18 . A pressure reducer  40  is disposed in the downstream channel  17  and has a hex head  42  and a sealing shoulder  43  that extend into the direction-changing cavity  16 , adjacent the upstream channel  11 . An upstream channel liner  50  is disposed in the upstream channel  11  and a downstream channel liner  80  is disposed in the downstream channel  17 . The channel liners  50  and  80  prevent erosion of the inner walls of the channels  11  and  17 , respectively, by the oil/sand mixture flowing from the oil well. A direction-changing cavity liner  60  is situated in the direction-changing cavity  16  to prevent erosion and wear of the inner wall of the direction changing cavity  16 . A key plate liner  70  is disposed in a key-plate recess  18  situated at an end of the direction-changing cavity  16  adjacent the downstream channel  17 . The key plate liner  70  prevents erosion and wear of the metal wall of the key-plate recess  18 . 
     An end cap  15  is provided to close off the direction changing cavity  16 . The end cap  15  is removable to permit access to the direction changing cavity  16  for installing and removing the direction changing cavity liner  60  and the key plate liner  70 . The end cap  15  can be unthreaded and removed to provide access to direction changing cavity  16 . The direction changing cavity liner  60  is removed by sliding it out of the direction changing cavity  16 . Once the direction changing cavity liner  60  is removed, the key plate liner  70  can be removed by tilting it out of key plate recess  18  and pulling it through the directional changing cavity  16  and out of the access opening. When the direction changing cavity liner  60  and the key plate liner  70  are removed, the hex head  42  of the pressure reducer  40  is accessible for removal or installation of the pressure reducer  40 . 
     End cap  15  has a port  13  formed therethrough to provide a connection point for a pressure gauge or other pressure sensing device. A second port  14  is formed in the body of pressure reducing valve  10  adjacent to the key-plate recess  18  to provide a connection point for a second pressure gauge or sensing device. 
     The upstream channel  11  is generally cylindrical and has an inlet portion characterized by a first diameter and an outlet portion  52  that is characterized by a second diameter smaller than the first diameter. The inlet portion and the outlet portion meet at an upstream channel maintenance point  12  which serves as a stop for the upstream channel liner  50 . Referring now to FIG. 3, there is shown an upstream channel liner  50  in accordance with the present invention. The upstream channel liner  50  is generally cylindrical and has an inlet portion and an outlet portion. The inlet portion has a diameter that is essentially commensurate with the inside diameter of the inlet portion of upstream channel  11  and the outlet portion has an outside diameter that is essentially commensurate with the inside diameter of the outlet portion of upstream channel  11 . That arrangement provides a shoulder stop  53  on the exterior of the upstream channel liner  50  which abuts the upstream channel maintenance point  12  when inner end  52  is inserted into the upstream channel  11 . The abutment of the shoulder stop  53  with the maintenance point  12  prevents the liner from shifting toward the direction changing cavity  16  when oil is flowing. The upstream channel liner  50  has an internal channel that extends from an opening  51  to the outlet portion  52 . The opening is preferably flared to lessen flow turbulence as the oil enters the upstream channel liner  50 . In the embodiment shown in FIG. 3, the internal channel tapers to a smaller cross section as it traverses the outlet portion  52 . The tapered channel portion  54  relieves some of the pressure and turbulent flow of the oil as it flows through the upstream channel  11 . The upstream channel liner  50  is formed of a ceramic material. 
     Shown in FIG. 4 is an alternative embodiment of the upstream channel liner  50 . In the embodiment shown in FIG. 4, the internal channel  55  has a uniform cross section to maximize flow. 
     Referring now to FIGS. 2,  5 A, and  5 B, the direction changing cavity liner  60  is disposed within the directional changing cavity  16  of pressure reducing valve  10 . The directional changing cavity liner  60  is formed of a ceramic material. The liner  60  is generally cylindrical and has an outside diameter that is dimensioned to provide a snug fit between the outer surface of the liner  60  and the inner surface of the cavity  16 . A recess  64  is formed in one end of the liner  60 . The recess is dimensioned to provide a space around the head  42  and shoulder  43  of the pressure reducer  40  when it is fully threaded into the downstream channel  17 . A central through-hole  61  extends along the length of the direction changing cavity liner  60  to provide a path between the recess  64  and the port  13  for pressure indication. The directional changing cavity liner  60  has a key-way  62  formed thereon which extends longitudinally partially along the exterior of direction changing cavity liner  60 . The directional changing cavity liner  60  also has a key plate thru-hole  63  formed therein between the recess  64  and the key-way  62  to provide fluid communication between recess  64  and port  14 . 
     Referring now to FIGS. 2,  6 A, and  6 B, the key plate liner  70  is positioned within the key plate recess  18  of reducing valve  10 . Key plate liner  70  contains a key plate thru-hole  71  which aligns with the key plate port  14  and the key plate thru-hole  63  to provide fluid communication between the recess  64  and the key plate port  14 . Key plate liner  70  also has a key  72  formed thereon which is dimensioned to mate with the key-way  62  in liner  60  to ensure proper alignment of the key plate liner  70  and the cavity liner  60 . The key plate liner  70  is formed of a ceramic material. 
     Referring now to FIGS. 2 and 7, the downstream channel liner  80  is disposed within the downstream channel  17 . The downstream channel  80  is generally cylindrical in shape and has an outside diameter that is dimensioned to provide a tight fit with the downstream channel  17 . Because of that arrangement, the downstream liner  80  prevents the oil from backwashing between the liner and the interior wall of downstream channel  17 . The downstream channel  80  extends less than the full length of the downstream channel  17  so that an attachment region is provided where the pressure reducer  40  can be attached to the body of the pressure reducing valve  10 . In the embodiment shown, the pressure reducer  40  is attached by threading it into the downstream channel  17 . The downstream channel liner  80  is formed of a ceramic material. 
     As shown in FIG. 2, pressure reducer  40  is situated in downstream channel  17  and projects into direction changing cavity  16 . Referring now to FIG. 8, there is shown a preferred arrangement for the pressure reducer  40 . The pressure reducer  40  is generally cylindrical and has an outside diameter that is substantially commensurate with the inside diameter of downstream liner  80 . A series of screw threads  44  are formed on the outer surface adjacent the shoulder  43 . The pressure reducer  40  is formed of a ceramic material. A central channel  45  extends longitudinally through the body of the pressure reducer  40  from entry port  41  to an outlet port  49 . The central channel  45  flares to a larger inside diameter to provide a pressure reducing effect as the oil flows from entry port  41  through the central channel. When the pressure reducer  40  is threaded into the downstream channel  17 , sealing shoulder  43  presses against a washer or gasket to provide a fluid-tight seal against the abrasive flow of oil and sand from direction changing cavity  16 . The washer or gasket is preferably formed of Buena-N gasket material or an equivalent thereof. 
     FIG. 9 shows an alternative embodiment of pressure reducer  40 . The embodiment shown in FIG. 9 has a generally cylindrical body including a head portion  92  with a plurality of entry holes  46  formed therein to provide an inlet for the oil. The pressure reducer  40  has a central channel  48  formed longitudinally therethrough. The central channel  48  has a substantially uniform cross section along its length and extends from the head portion  92  to an outlet port  94  in the other end of the pressure reducer  40 . The entry holes  46  are in fluid communication with the central channel  48 . A hexagonal shoulder  47  is formed about the circumference of the pressure reducer  40  adjacent the head portion  92 . The hexagonal shoulder  47  performs the functions of the hex head  42  and shoulder  43  of the embodiment shown in FIG.  8 . 
     Referring back to FIG. 2, upstream cylindrical liner  50  and downstream cylindrical liner  80  are removed by un-bolting flange connections at both ends of reducing valve  10 , removing reducing valve  10  from the process piping, and sliding upstream cylindrical liner  50  and downstream cylindrical liner  80  out of upstream canal  11  and downstream canal  17 , respectively. The liners are installed by reversing this process. 
     Referring now to FIG. 10, there is shown a spool assembly including a first spool adapter  20  and second spool adapter  30 . First spool adapter  20  has a steel body with a central longitudinal channel  21  having a substantially uniform cross section along the length thereof. A ceramic channel liner  22  having a substantially uniform outside diameter  23  that is dimensioned to provide a light press fit in the central channel  21  of first spool adapter  20 . The ceramic channel liner  22  extends substantially the entire length of the central channel  21 . Channel liner  22  has a flow channel  24  that extends the length of the channel liner  22 . The cross section of the flow channel  24  gradually widens in the direction of the oil flow from the inlet of the spool adapter  20  adjacent the pressure reducing valve  10  to its outlet adjacent the second spool adapter  30 . The gradual widening or flaring of the flow channel  24  minimizes turbulent, abrasive, flow that would aggravate the wear and erosion caused by the flow of oil and sand therethrough, thus increasing the useful life of the spool adapter  20 . 
     The second spool adapter  30  has a steel body with a central longitudinal channel  31 . A ceramic channel liner  32  has a substantially uniform outside diameter  33  that is dimensioned to provide a light press fit in the central channel  31  of second spool adapter  30 . Ceramic channel liner  32  has a flow channel  36  that extends from the inlet adjacent the first spool adapter to the outlet adjacent the downstream process piping (not shown). The central channel  36  has a flared portion  34  and a uniform cross section portion  35 . The flared portion  34  extends from the inlet along part of the length of ceramic liner  32 . The degree of flaring is such as to continue the flaring of the flow channel  24  of the first spool adapter  20 . The inside diameter of the uniform cross section portion  35  is dimensioned to be commensurate with the inside diameter of the downstream process piping. 
     As described above, the pressure reducer  40 , upstream channel liner  50 , direction changing cavity liner  60 , key plate liner  70 , downstream channel liner  80 , and the central longitudinal channel liners  22  and  32 , are all formed of a ceramic material. The ceramic material is selected from the class of technical ceramics, particularly technical ceramic materials that exhibit superior wear resistance and strength. Among the preferred ceramic materials are aluminum oxide (alumina), chromium oxide, high alumina, titanium oxide (titania), zirconium oxide (zirconia) ceramics, including fully and partially stabilized zirconia, and combinations of such metal oxides. It is believed that just about any type of metal-oxide ceramic will provide acceptable properties. Excellent results have been achieved using partially stabilized zirconia (PSZ) for making the aforesaid components. Particular species of PSZ that are believed to be useful for the aforesaid components include Mg-PSZ and vitreous PSZ. Silicon nitride, quartz, and silicon carbide ceramics are also expected to be useful in such components. 
     Referring now to FIG. 11, there is shown an alternative embodiment of a pressure reducing valve according to the present invention. The pressure reducing valve  110  has a metallic body  120  that includes an upstream channel  111  and a downstream channel  117 . Upstream channel  111  has an inlet portion  115  and an outlet portion  116  which meet at a maintenance point  112 . An upstream channel liner  150  is disposed in the upstream channel  111 , and likewise, a downstream channel liner  180  is disposed in the downstream channel  117 . Channel liners  150  and  180 , among other things, prevent erosion of the inner walls of the channels  111  and  117 , respectively, by the oil/sand mixture flowing through pressure reducing valve  110 , from the oil well. A gauge port  114  is formed in the metallic body  120  to provide a connection point for a pressure gauge, or other sensing device. Gauge port  114  has one end in communication with downstream channel  117 . 
     Upstream channel liner  150  is slidably disposed within upstream channel  111 . As shown in FIG. 12, the upstream channel liner  150  is generally cylindrical and has an inlet portion  151 , which is characterized by a first diameter, and an outlet portion  152 , which is characterized by a second diameter smaller than the first diameter. Inlet portion  151  has an outside diameter that is essentially commensurate with the inside diameter of the inlet portion  115  of upstream channel  111  and the outlet portion  152  has an outside diameter that is essentially commensurate with the inside diameter of the outlet portion  116  of upstream channel  111 . That arrangement provides a shoulder  153  which abuts the maintenance point  112  when channel liner  150  is inserted into upstream channel  111 . The abutment of shoulder  153  with maintenance point  112  prevents the liner  150  from shifting toward downstream liner  180  when oil is flowing through reducing valve  110 . The upstream channel liner  150  has an internal channel  154  that extends from the inlet portion  151  to the outlet portion  152 . Channel  154  is preferably tapered to lessen flow turbulence as oil flows through upstream channel liner  150 . In the embodiment shown in FIG. 12, the internal channel tapers to a smaller cross section as it traverses to the outlet portion  152 . The upstream channel liner  150  is preferably formed of a ceramic material as described above. 
     Downstream channel liner  180  is slidably disposed in the downstream channel  117 , as shown in FIG.  11 . Referring now to FIG. 13, downstream channel liner  180  is generally cylindrical and has an inlet end  181  and an outlet end  182 . Downstream channel liner  180  has a through-hole  183 , which is oriented and positioned to align with gauge port  114 . Through-hole  183  extends radially through channel liner  180  and is in fluid communication with internal channel  184  of the channel liner  180 . A recess  185  is formed in liner  180 , at the inlet end  181 . Recess  185  is generally cylindrical in shape and is dimensioned and positioned to receive the inner end  155  of upstream liner  150 . Channel  184  extends between the inlet end  181  and the outlet end  182  of liner  180 . Channel  184  is flared near outlet end  182  to minimize turbulent flow that would aggravate the wear and erosion caused by the flow of oil and sand. Downstream channel liner  180  is preferably formed of a ceramic material as described above. 
     In connection with this embodiment of the invention, a pressure reducing valve has been described which has only upstream and downstream ceramic liners. These ceramic liners are slidably disposed in the fluid flow channels of the pressure reducing valve assembly to protect the metallic walls of the channels from erosive wear. Furthermore, the pressure reducing valve of this embodiment has fewer components than the first-described embodiment and thus, is easier to assemble and disassemble. The upstream liner interconnects with the downstream liner, so as to keep them both securely in place. 
     It can be seen from the foregoing description and the accompanying drawings that the present invention provides a novel means for extending the operating life of high pressure oil well components and for maintaining desired operating pressures by substantially reducing the rate of abrasive wear to components in a pressure reducing assembly for a high pressure oil well head. Although the invention has been described with reference to specific components and assemblies thereof, including a ceramic pressure reducer, a ceramic-lined reducing valve, and ceramic-lined spool pipe adapters, it is contemplated that any metal component in such a pressure reducing assembly that is subject to erosive wear caused by the flow of an oils/and mixture under very high pressure can be formed from or lined with a ceramic material to substantially reduce the rate of wear and erosion. A distinct advantage of the present invention is that a high pressure oil well, incorporating ceramic components in accordance with this invention, can be operated at the desired high well pressures while keeping the sand content low. The desired high pressures can be maintained over a much longer period of time than obtainable with known components because component deterioration is minimized. Lost oil production resulting from well down-time, during spent component replacement, is drastically reduced, because of the increased wear resistance and more efficient flow design of the ceramic components. 
     It will be recognized by those skilled in the art that changes or modifications may be made to the above described embodiments without departing from the broad, inventive concepts of the invention. It is understood, therefore, that the invention is not limited to the particular embodiment(s) disclosed, but is intended to cover all modifications and changes which are within the scope and spirit of the invention as defined in the appended claims.