Abstract:
A submersible pump assembly may be radially oriented for pumping well fluid in a deviated or horizontal well. The submersible pump assembly has an instrument housing having a longitudinal axis and incorporated onto the pump assembly. An electrical contact is mounted within the housing and an electrical contact probe, moveable relative to the housing and biased upwards toward an upper side of the housing when the pump assembly is inclined, is provided. The housing and the electrical contact are rotatable about the longitudinal axis relative to the electrical contact probe, such that an electrical circuit is completed when the electrical contact is rotated into engagement with the electrical contact probe, generating a signal from the completed electrical circuit. The electrical contact is at a known circumferential position relative to the fixed reference point, which may be the intake port of the pump.

Description:
FIELD OF THE INVENTION 
     The present invention relates in general to downhole sensors and, in particular, to an improved system, method and apparatus for a downhole orientation probe sensor, such as for electrical submersible pump applications. 
     BACKGROUND OF THE INVENTION 
     Submersible pumping systems, such as electrical submersible pumps (ESP) are often used in hydrocarbon producing wells for pumping fluids from within the well bore to the surface. ESP systems may also be used in subsea applications for transferring fluids, for example, in horizontal conduits or vertical caissons arranged along the sea floor. 
     Pumps become less efficient when significant amounts of gas from the well fluid flow into the intakes. In a horizontal or highly deviated well, any gas in the well fluid tends to migrate to the upper side of the casing, forming a pocket of free gas. The gas tends to flow into a portion of the intake on the higher side of the pump intake. 
     Current solutions to this problem include gas restrictors, such as that described in U.S. Pat. No. 6,715,556, and gas separators, such as that described in U.S. Pat. No. 7,270,178. While the prior art types may be workable, they often have multiple moving parts which make them more complicated than necessary, increasing production costs and increasing the likelihood of mechanical failure. Another current prior art alternative would be to drill a sump with multilaterals but this method can add hundreds of thousands of dollars to drilling and production costs. 
     SUMMARY 
     Disclosed herein are a system, method, and apparatus for a downhole orientation probe sensor, such as that for electrical submersible pump applications. 
     The ability to know the radial position or orientation of downhole tools, including Electric Submersible Pumps (ESPs) and attachments or enhancements is of significant value. The term radial position means the particular position that a selected point on the circumference of the ESP is located relative to a true vertical direction while the ESP is in an inclined well, such as a horizontal or highly deviated well. For example, the selected point may be desired to be on the bottom side of the ESP while the ESP is inclined. 
     Knowing the actual radial position of the tool gives the operator the ability to adjust the equipment by simply rotating the tubing string to the desired position. This ability provides benefits such as the ability to position a pump with a limited number of intake holes in a horizontal well, such that the intake holes are at the bottom for maximum liquid draw. Another benefit is the ability to position the cable or motor lead for minimal stress as it is installed through a deviated well-bore. In this way, downhole equipment could be designed so that the location of the cable or motor lead is optimized and in the case of an ESP with a limited number of intake holes, the position of the intakes relative to the position of the cable or motor lead could be optimized. For example, the intakes could be located circumferentially around only a portion of the pump with the expectation that these intakes be positioned at the bottom of a horizontal well and the cable or motor lead could be positioned circumferentially relative to these intakes so that they are not sandwiched between the pump and the bottom of the horizontal well but are instead placed on top or in the preferred embodiment, placed along the side of the equipment and string in the well. 
     In addition the ability to radially position downhole equipment could also optimize the installation of various production-aiding devices that enhance production in horizontal or highly deviated wellbores such as a shroud or inverted shroud. For example, the shroud might have a closed base and a closed top with an inlet port on the sidewall of the shroud near the top. Radially orienting the shroud places the inlet port on the bottom side of the shroud. Any aid to increase production from horizontal wells is a significant asset. 
     Such a downhole sensor comprises a weighted sensor switch which could be included in the module containing other downhole sensors such as ones measuring pressure and temperature. The weighted sensor switch would be employed to give a feedback signal to the surface instruments to indicate the radial position of the downhole equipment, such as the ESP string, or any other tubing string. In practice, as the string is being lowered and when it reaches its final location, the downhole sensor device sends a signal to indicate equipment radial orientation in horizontal or highly deviated wellbores. 
     According to one aspect of the invention an apparatus for pumping well fluid in a deviated or horizontal well, comprises a submersible pump assembly adapted to be secured to a string of tubing and lowered into a well. An instrument housing having a longitudinal axis is incorporated into the pump assembly. An electrical contact is mounted within the instrument housing. An electrical contact probe, moveable relative to the housing, is biased upwards toward an upper side of the housing when the pump assembly is inclined. The housing and the electrical contact are rotatable about the longitudinal axis relative to the electrical contact probe, such that an electrical circuit is completed when the electrical contact is rotated into engagement with the electrical contact probe. An electrical circuit is completed when the stationary electrical contact contacts the moveable electrical contact probe, such that the position of the fixed reference point relative to a true vertical line can be determined from a signal generated from the completed electrical circuit. 
     According to another aspect of this invention, an apparatus for pumping well fluid in a deviated or horizontal well, comprises a submersible pump assembly adapted to be secured to a string of tubing and lowered into a well. A cylindrical fluid and gas tight housing is attached to the pump assembly, the housing having a longitudinal axis. An electrical contact ring is mounted to but insulated from an inner surface of the housing. The contact ring has a plurality of electrically conductive segments and encircles the axis of the housing. A fulcrum has an inner end located on the axis and an outer end mounted to the inner surface. A resistor is electrically connected to each conductive segment, each resistor having a unique resistance. A cantilever has an intermediate point pivotally mounted on the inner ends of the fulcrum, the housing being rotatable about the axis relative to the cantilever. An electrically conductive contact probe is situated at one end of the cantilever and a weight is attached to an opposite end of the cantilever. Electrical leads extend from the resistors and from the probe to a power source. The weight causes the contact probe to come into contact with one of the conductive segments to complete an electrical circuit, providing a signal that determines which segment is in contact with the probe. 
     According to another aspect of this invention, a method for determining the radial orientation of a fixed reference point of an ESP in a deviated or horizontal well, comprises mounting to the ESP a housing having an axis, the housing having an electrical contact offset from the axis of the housing. An electrically conductive probe is pivotally mounted in the housing and biased upward. When the ESP is at the desired depth in an inclined portion of a well, the operator rotates the ESP and the housing about the longitudinal axis while the probe remains stationary, until the electrical contact rotates into engagement with the probe. This contact completes an electrical circuit, passing a current through the completed electrical circuit, and generating a signal by the completed electrical circuit to determine the position of the fixed reference point relative to a true vertical line. 
     The foregoing and other objects and advantages of the present invention will be apparent to those skilled in the art, in view of the following detailed description of the present invention, taken in conjunction with the appended claims and the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Some of the features and benefits of the present invention having been stated, others will become apparent as the description proceeds when taken in conjunction with the accompanying drawings, in which: 
         FIG. 1A  is a schematic drawing of a deviated well with an ESP and the probe sensor of the present invention; 
         FIG. 1B  is a schematic drawing of an alternative embodiment of a deviated well with an ESP and the probe sensor of the present invention; 
         FIG. 1C  is a schematic drawing of another alternative embodiment of a deviated well with an ESP and the probe sensor of the present invention; 
         FIG. 2  is a cross-sectional side elevation view of the probe sensor; 
         FIG. 3  is a cross-sectional view perpendicular to the axis of the well at the probe sensor of the present invention; 
         FIG. 4  is a second cross-sectional view perpendicular to the axis of the well at the fulcrum of the present invention; and 
         FIG. 5  is a schematic cross-sectional view of the probe sensor and ESP of the present invention. 
     
    
    
     While the invention will be described in connection with the preferred embodiments, it will be understood that it is not intended to limit the invention to that embodiment. On the contrary, it is intended to cover all alternatives, modifications, and equivalents, as may be included within the spirit and scope of the invention as defined by the appended claims. 
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention will now be described more fully hereinafter with reference to the accompanying drawings in which embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the illustrated embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout. 
     Referring Initially to  FIG. 1A , a pump  10 , seal assembly  12 , motor  14 , and sensors  16  may be suspended from tubing  18  within a wellbore casing  20  that traverses a subterranean formation. In an exemplary embodiment, the casing  20  may be positioned in a highly deviated or horizontal orientation and may contain liquid materials  22  and gaseous materials  24 . Thus, due to the relative buoyancy of the gaseous materials  24 , in an exemplary embodiment, a lower portion of the casing  20  may contain the liquid materials  22  and an upper portion of the casing may contain the gaseous materials  24 . Pump  10  includes an intake portion  26  which may consist of a series of intake ports  28  on a lower portion of the surface of intake portion  26  while pump  10  is oriented horizontally. Preferably there are no intake ports  28  on the upper side of intake portion  26 . A motor lead  36  is connected to motor  14  to provide three phase AC power and other signals to motor  14 . 
     Referring to  FIG. 1B , cased borehole  11  illustrates a typical well having an inlet comprising perforations  21  for the flow of well fluid containing gas and liquid into cased borehole  11 . A string of tubing  18  extends downward from the surface for supporting pump  10 . A shroud  13  is mounted in an inverted manner in the embodiment of  FIG. 1B . Shroud  13  has a closed base end  15  that is secured sealingly around the pump assembly a short distance below pump intake ports  28 . Shroud  13  has a closed head end  17  that is located above pump  10  in this example and secured sealingly around tubing  18 . Shroud  13  has one or more shroud inlets  23  located near head end  17 . When oriented radially and shroud in an inclined position, inlet  23  will be situated along the lower side of shroud  13 . The length of shroud  13  depends upon the content of gas in the well fluid, and it could be several hundred feet long. The inner diameter of shroud  13  is larger than the outer diameter of pump  10  in this embodiment, creating a shroud annulus  19  between them. 
     In the operation of the embodiment illustrated by  FIG. 1B , the well fluid flows from perforations  21  past most of the length of shroud  13 . At the head end  17  of shroud  13 , the well fluid flow changes direction to flow through shroud inlet  23  into shroud annulus  19 . When changing direction, some of the gas bubbles in the well fluid, particularly the larger volume gas bubbles, will continue flowing upward in cased borehole  11  for collection at the surface. 
     In the alternate embodiment of  FIG. 1C , shroud  25  is mounted over a portion of the pump assembly. In this embodiment, shroud  25  has a closed base end  27  that is located below pump intake ports  28  and a closed head end  29  located above intake ports  28 . Closed upper end  29  need be located only a short distance above intake ports  28 , but it could be located higher if desired, even above pump  10 . Shroud  25  has one or more inlets  23  near base end  27 . Preferably, shroud  25  fully encloses motor  14  so that well fluid flowing through inlet  23  of shroud  25  near base end  27  will flow past motor  14  for cooling. Shroud  25  is radially oriented when in an inclined position such that inlet  23  is situated along the lower side of shroud  25 . 
     In the operation of the embodiment of  FIG. 1C , well fluid flows from perforations  21  farther into the well, and some gas will separate from the well fluid at perforations  21  due to the buoyant force. The well fluid flows along the casing annulus surrounding shroud  25  and into inlet  23  of shroud  25  near base end  27 . The well fluid flows up the interior of shroud  25  into intake ports  28 . In the embodiments of  FIGS. 1B and 1C , intake ports  28  may be situated all around the surface of intake portion  26  or may only be on a lower portion of the surface of intake portion  26 . 
     Referring next to  FIG. 2 , the sensors  16  may include a number of sensing devises, including the probe sensor  30  of the current invention as well as pressure and temperature sensors. Sensors  16  are typically powered by rectifying a portion of the AC power supplied down motor lead  36  to motor  14 . The components of probe sensor  30  are situated inside a fluid and gas tight sensor housing or shell  32  to protect the components of the probe sensor  30  from the liquid material  22  and gaseous material  24  inside the wellbore casing  20 . The components of probe sensor  30  include a long cylindrical cantilever  34 . Cantilever  34  has a weight  38  on one end and a contact probe  40  on the opposite end. In the preferred embodiment of  FIG. 2 , contact probe  40  and weight  38  are both spherical in shape but they may also comprise other convenient shapes such as a box, egg or dome shaped. Contact probe  40  is made of electrically conductive material. A wire extends from contact probe  40  along or within cantilever  34 . 
     In the preferred embodiment, a mid-section of cantilever  34  is held in place by at least two fulcrums  42 . The outer end  44  of each fulcrum  42  is secured to a first ring shaped electrical insulator  46  which is attached to the inner surface  50  of sensor shell  32 . The inner end  48  of each fulcrum  42  is in contact with a mid-section of cantilever  34 . As seen in the preferred embodiment of  FIG. 2  and  FIG. 4 , the inner end  48  of each fulcrum  42  is rounded and such rounded inner end  48  is situated within an indent  52  in fulcrum  42 . The positioning of inner end  48  within indent  52  allows sufficient freedom of movement so that the contact probe  40  of cantilever  34  is able to rotate a full 360 degrees within the inner circumference  54  of the ring of radial laminations  56  while each fulcrum  42  maintains contact with cantilever  34 . Alternative methods of joining the inner end  48  of each fulcrum  42  to cantilever  34  may be employed such as a ball and socket joint. Additionally, alternative means may be used for providing a pivot point for cantilever  34  such as a single fulcrum or 3 or more fulcrums. Alternatively, the two fulcrums could be replaced by a circular disk having a hole in its center and mounted perpendicular to the axis of shell  32 . 
     As seen in  FIG. 3 , in the preferred embodiment, the ring of electrically conductive radial laminations  56 , which act as stationary electrical contacts, comprise a series of segments or laminations which together form a ring. The outer surface  58  of such ring of laminations  56  is in contact with an inner surface  68  of a second ring shaped electrical insulator  60 , which is attached to the inner surface  50  of sensor shell  32  at an axial distance  62  from the first insulator  46 . Returning to  FIG. 2 , in the preferred embodiment, each segment of laminations  56  is connected to a resistor  64 , each resistor having a unique resistance. Each lamination segment  56  is spaced apart from adjacent segments  56  by clearances or insulators. Each resistor  64  is connected to a resistor lead  66  which in turn is connected to one of the fulcrums  42 . When probe  40  touches any of the laminations  56 , an electrical circuit is completed. 
     The route of the circuit in the preferred embodiment of  FIG. 2  is from the contact probe  40 , through the lamination  56  to resistor  64 , to resistor lead  66  through fulcrum  42  to the cantilever  34  to return to the contact probe  40 . The source of power (not shown) for the circuit may be from motor  14  ( FIG. 1 ) and may be connected to the resistor or the fulcrum or any other place within the circuit which is convenient. Because each resistor  64  has a unique resistance, by passing a current through the circuit from a known voltage and measuring the current or the change in voltage, the resistor, which is part of the circuit, can be identified and the radial orientation of the probe sensor  30  can be determined. The width of probe  40  and spacing of the lamination segments  56  are such that electrical contact is made between probe  40  and one or two distinct lamination segments  56  at any one time. The resistance of each of the resistors  64  is such that if probe  40  contacts two lamination segments  56  at the same time, the total resistance measured would be distinct and observable so as to deduce the exact position of probe  40 . 
     Alternatively, the resistors  64  may not be necessary where an alternative means of measurement over a completed electrical circuit may be used such as different or unique power frequencies supplied to each segment of laminations. In an alternative embodiment, a single electrically conductive radial lamination may be provided and located in such a position within the probe that the circuit will only be completed when the optimal orientation of the downhole equipment is achieved. 
     The transmission of the signal from the sensor to the surface can be achieved by imposing the signal on motor lead  36  and the power cable leading to the surface. Alternatively, the signal may be transmitted by remote signal, or by any other means known in the art. After the radial orientation of the equipments has been determined, the operator can rotate the tubing  18 , causing the pump  10 , intake  26  and motor  14  to rotate until the optimal radial orientation of the equipment is achieved. 
     In operation, shell  32  is attached to motor  14  in a radial orientation that causes probe  40  to contact a selected one of the laminations  56  while the pump assembly is horizontal or inclined. The particular resistor  64  for that lamination  56 , referenced herein as the reference resistor  64 , will be on the uppermost point of shell  32  while a reference point on the pump assembly is spaced a desired circumferential distance away from the lamination  56  for reference resistor  64 . For example, in the embodiment of  FIG. 1A , the reference point comprises intake port  28 , the center of which will be spaced relative to the longitudinal axis 180 degrees away from the lamination  56  for reference resistor  64 . The resistance of the reference resistor  64  is known. Being 180 degrees away, the center of intake port  28  and the center of the lamination  56  for reference resistor  64  will be in the same plane that contains the longitudinal axis of the pump assembly. When the pump assembly is inclined with intake port  28  on the lowermost side and lamination  56  for reference resistor  64  on the uppermost side, this plane will be in a true vertical orientation. 
     The operator runs the pump assembly into the well on a string of tubing  18 . When the pump assembly is at a desired depth, it will be inclined or horizontal. As shown in  FIG. 2 , weight  38  at one end of fulcrum  42  will be pulled downwards due to the force of gravity, causing contact probe  40  to rise and come into contact with one of the radial laminations  56 , completing an electrical circuit. The operator detects the signal caused by the completed circuit, which determines whether the reference resistor  64  is at the uppermost side of shell  32 . If not, the operator rotates tubing  18 , which causes the pump assembly and shell  32  to rotate. Contact probe  40  does not rotate with shell  32 , rather touches each lamination  56  as such laminations rotate past. A different signal is sent as probe  40  touches each lamination  56 . When the reference resistor  64  is touching probe  40 , the signal will inform the operator that the reference resistor  64  is now on the uppermost side of the pump assembly and the intake port  28  on the lower side relative to true vertical. For certain wells, such as those producing liquid and gas, locating the intake port  28  in the bottom rather than the top is preferred. This position reduces gas flow into pump  10 . 
     Rather than spacing lamination  56  for the reference resistor  64  relative to intake port  28 , the operator may space lamination  56  for the reference resistor  64  a selected number of degrees from a reference point that is where motor lead  36  joins motor  14 . Preferably, once the pump assembly is radially oriented in an inclined part of the well, motor lead  36  will be at a position other than on the bottom of the pump assembly and pushed into contact with casing  20  by the weight of the pump assembly. For example, motor lead  36  could join motor  14  at a point between 90 to 180 degrees away from the lamination  56  of reference resistor  64 . This would place motor lead  36  equal to or above the longitudinal axis of the pump assembly when the lamination  56  for the reference resistor  64  is at its uppermost point when the pump assembly horizontal.  FIG. 1A  and FIG  5  shows motor lead  36  at about 90 degrees relative to the lowermost side and uppermost side of the pump assembly. As seen in FIG  5 , which schematically illustrates the relative position of probe  40  of sensor  30  relative to the motor lead  36 , of the pump assembly, when motor lead  36  is at about 90 degrees relative to the lowermost side and uppermost side of the pump assembly, motor lead  36  at an equal elevation with the longitudinal axis of motor  14  of the pump assembly. In practice, the operator would install the pump assembly into the well and just after the unit has started to angle toward the horizontal, the operator would stop the installation and check the orientation of motor lead  36  by using process described above. Adjustments to the orientation of motor lead  36 , if required, can be made then installation would resume until the pump assembly has landed at the final location. Periodic checks could be made as the pump assembly passes through the deviation. 
     Referring to  FIGS. 1B and 1C , the operator may space lamination  56  for reference resistor  64  approximately 180 degrees from shroud inlet  23  relative to the longitudinal axis of the pump assembly. When inclined and the lamination  56  for reference resistor  64  on the uppermost side of the pump assembly, shroud inlet  23  will be on the lower side of the pump assembly. 
     While the invention has been shown or described in only some of its forms, it should be apparent to those skilled in the art that it is not so limited, but is susceptible to various changes without departing from the scope of the invention. For example, weight  38  on the end of cantilever  34  could serve as an electrical conductor, allowing electrical conductor  40  to be eliminated. In that event, laminations  56  would be placed so as to be contacted by weight  40 , and the intake  28  or shroud inlet  23  could be circumferentially aligned with each other, rather than 180 degrees apart. The center of the lamination  56  for the reference resistor  64  would still be in the same vertical plane with the center of the reference point, whether it is intake  28  or shroud  23 . Also, it is not necessary that the lamination for the reference resistor and the particular reference point be in the same vertical plane as long as the circumferential degree spacing apart from each other is known.