Abstract:
The present disclosure provides a dis-connectable wellhead hanger arrangement permitting a pig tail set of a electrical conductors to be inserted within the wellhead hanger arrangement which seals against the wellhead hanger upon separation of an electrical power cable. If the power cable separates from the production tubing for any reason, the compressively fit plugs disconnect the power cable from the pathway leaving the electrical mandrel sealed within the wellhead hanger, thereby sealing the wellhead hanger from loss of fluid after separation.

Description:
[0001]    This application claims priority to U.S. Provisional Application No. 61/823,054, filed May 14, 2014, and No. 61/863,086, filed Aug. 7, 2013, which are incorporated by reference herein as if copied verbatim in their entirety. 
     
    
     FIELD OF INVENTION 
       [0002]    The present invention relates to an electrical connector for use in a well; and, more specifically, to a dis-connectable dielectric grease-packed plug that purposefully preserves pressure within a well bore upon separation of an electrical conductor bundle from a wellhead hanger connection. 
       BACKGROUND OF INVENTION 
       [0003]    Occasionally, but fortunately not often, the production tubing on an oil and gas well will fail or “part” (i.e., separate), due to corrosion problems or other severe well conditions. Most often, the tubing will separate at a threaded connection, like a coupling, or at the wellhead tubing hanger, then fall down the well bore. On a well that includes an electrical submersible pump, or down-hole heater, a power cable is fixed to this production tubing, and attached to a wellhead penetrator, or is used on a “feed-thru” type design. If the production tubing parts or separates, it will drop downward, pulling the power cable with it. This puts a severe strain on the fixed electrical penetrators at the surface wellhead, and often negates their sealing capabilities. High-pressure well fluids can then escape from the wellhead into the atmosphere. Currently, a wellhead penetrator that can maintain a reliable and expected seal upon a separation of a tubing connection, or is purpose-built to handle this catastrophic failure, does not exist. However, Applicants have developed a dis-connectable wellhead hanger connection which, if downward force is applied to the connection, allows a “clean” separation, leaving a reliable seal in the tubing hanger and preventing well fluids from escaping into the atmosphere. Typically, prior connections were made with cleaned pins inserted in a dry female plug. A new pin structure and method of installation is described covering the male pin with a dielectric grease facilitating the connection process and eliminating all air pockets around the pin thereby insuring a connection unlikely to blow apart upon significant changes of pressure within the wellhead under operation. 
       SUMMARY OF INVENTION 
       [0004]    This well bore connector comprises a wellhead hanger adapted to seat in a well head; an electrical connector mandrel inserted in the wellhead hanger; a female pin connection socket inserted in the electrical connector mandrel; a mini-mandrel or feed through assembly inserted in the wellhead hanger having one or more electrical conductors sealed within the mandrel and extending from the mandrel; a male pin attached to a stripped end of an electrical conductor extending from the mini-mandrel or feed through assembly inserted into the female pin socket; a dis-connectable connection between the female pin socket and male pin within the wellhead hanger, permitting separation of the mini-mandrel or feed through assembly from the electrical connector mandrel, sealing the well bore to prevent fluids from release upon disconnection. 
         [0005]    The well bore connector provides a shoulder within the wellhead hanger to seat the electrical connector mandrel and provides O-rings to seal the electrical connector mandrel in the wellhead hanger to inhibit migration of fluids up the wellhead hanger. The electrical connector mandrel of the well bore connector is fabricated from polyether ether ketone (PEEK) and provides a shoulder to seat the female pin socket within the mandrel and a snap ring to retain the female pin socket within the mandrel. Additionally, the exterior of the female pin socket provides O-rings to seal against migration of fluids up the interior of the electrical connector mandrel and the interior of the female pin socket provides contact bands to establish a low resistance electrical connection with the male pin. 
         [0006]    Moreover, the well bore connector described herein seals the exterior of the mini-mandrel or feed through assembly with O-rings against migration of fluids up the interior of the electrical connector mandrel and the wellhead hanger. The interior of the mini-mandrel or feed through assembly is preferably filed with epoxy around each of the one or more electrical conductors. 
         [0007]    The well bore connector can also provide the electrical connector mandrel a stainless steel collar between the wellhead hanger shoulder and the shoulder on the electrical connector mandrel which inhibits excessive deformation of the electrical connector mandrel in hot, high temperature wells. 
         [0008]    Additional features that can be provided by this device include: threads for connection of a wellhead sub assembly to the electrical connector mandrel or an annular space permitting the packing of the wellhead hanger with a dielectric grease on the surface side of the wellhead hanger to inhibit the ingress of water or other contaminants into the electrical connector mandrel. 
         [0009]    The well bore connector can also provide the electrical connector mandrel with threads for connection of a wellhead sub assembly to the electrical connector mandrel and a wellhead hanger which provides threads for connection of the wellhead sub assembly to the wellhead hanger. 
         [0010]    The exterior surface of the male pin of the well bore connector provides a longitudinal slot or groove permitting excess dielectric grease covering the male pin, prior to insertion with the female pin socket, to be extruded. 
         [0011]    Applicants also claim a well bore connector assembly connected in a wellhead hanger comprising an electrical connector mandrel inserted in the well-bore connector assembly; a female pin connection socket inserted in the electrical connector mandrel; a mini-mandrel or feed through assembly inserted in the well-bore connector assembly having one or more electrical conductors sealed within the mandrel and extending from the mandrel; a male pin attached to a stripped end of an electrical conductor extending from the mini-mandrel or feed through assembly inserted into the female pin socket; a dis-connectable connection between the female pin socket and male pin, within the well-bore connector assembly permitting separation between the electrical connector mandrel from the mini-mandrel, sealing the well bore and the well-bore connector assembly to prevent fluids from release upon disconnection. This unitary device could be assembled off-site and installed with a compatible wellhead hanger without undue delay. Each of the features of this device replicate the features of the well bore connector previously described herein. 
         [0012]    This application also claims a method for installing a dis-connectable electrical connection for use in a wellhead hanger which can comprise the steps of connecting a female pin connector socket to a stripped end of a upper pig tail conductor; inserting the female pin connector socket into an electrical connector mandrel until an upper end of the female pin socket seats against an internal shoulder within the electrical connector mandrel; connecting a male pin connector socket to a stripped end of a lower electrical conductor; and, inserting the male pin connector through a snap ring for insertion in the electrical conductor mandrel until the male pin engages a plurality of contact bands within the female socket end and the snap ring engages in a channel formed within an interior surface of the electrical connector mandrel. 
         [0013]    The method of assembly can further comprise the step of covering the male pin with dielectric grease before insertion in the female pin socket to prevent ingress of fluids into the pin connection and inserting the completed assembly into a wellhead hanger. Assembly of the well bore connector assembly is readily accomplished. The assembly would be completed and taken to the wellhead having an appropriate wellhead hanger and inserted in the wellhead hanger and screwed into place by the technician retaining the complete assembly in the wellhead. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]      FIG. 1  is a cross-sectional side view of the dis-connectable pressure-preserving electrical connector threaded into a wellhead. 
           [0015]      FIG. 1A  is an end view of the three conductors in the seal sub showing the spatial distribution of each in the dis-connectable pressure-preserving electrical connector of the present invention. 
           [0016]      FIG. 1B  is an exploded view of the various elements of the wellhead hanger and electrical connector mandrel disconnected from the mini-mandrel or feed through assembly of the upper connection and from the electrical cable set. 
           [0017]      FIG. 2  is cross-sectional side view of an alternative embodiment of the dis-connectable pressure-preserving electrical connector seated on a steel collar and threadable into a seal sub assembly located on the wellhead external surface. 
           [0018]      FIG. 2A  is an exploded side view of the elements of the embodiment shown in  FIG. 2 . 
           [0019]      FIG. 3  is a cross-sectional side view of the invention showing the connection to the seal sub assembly inserted into a groove in the wellhead hanger and showing an annular void at the wellhead groove for insertion of packing material. 
           [0020]      FIG. 3 a    is an exploded side cross-sectional view of each of the parts of the embodiment shown in  FIG. 3 . 
           [0021]      FIG. 4  is another embodiment of the dis-connectable pressure-preserving electrical connector threadably engaging a seal sub assembly inserted in the top of a wellhead hanger. 
           [0022]      FIG. 4A  is an exploded side cross-sectional view of the embodiment described in  FIG. 4 . 
           [0023]      FIG. 5  describes the components of the dis-connectable pressure-preserving electrical connector showing the point of separation of the mini-mandrel or feed through assembly from the electrical connector mandrel which remains sealed within the wellhead hanger. 
           [0024]      FIG. 6  is a detailed drawing of the female pin socket connected to the stripped end of the first electrical conductor entering from the surface and the male pin connector having a longitudinal slot or groove, which is attached with set screws to the stripped end of the second electrical conductor extending into the well bore. 
           [0025]      FIG. 7  is a cross-sectional side view of another embodiment showing a mandrel seated within a wellhead hanger and connected to an internal electrical connector mandrel having a canned pump coupler which permits a dis-connectable pressure-preserving seal if the production tubing and the attached electrical cable connector part from the wellhead hanger. 
           [0026]      FIG. 8  is an exploded view of the embodiment described in  FIG. 7  above. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0027]      FIG. 1  shows an embodiment of this invention providing an electrical connector mandrel  103  installed into a wellhead hanger  101 . The electrical connector mandrel  103  seated on interior wellhead shoulder  104  and is sealed within the wellhead hanger  101  with O-rings  123  thereby preventing fluid under pressure from leaking out of the well bore. Surface power cable leads or pigtails  111  are inserted into the interior of the wellhead hanger  101 , then into the electrical connector mandrel  103 . While only one electrical cable is shown in  FIG. 1  on the interior of the electrical connector mandrel  103 , there are three such conductors for the three-phase electrical power required by all modern ESPs. The relative position of each of these conductors is more fully shown in  FIG. 1 a    that shows a cross-sectional view of the three conductors  111  in electrical connector mandrel  103  seated within the wellhead hanger body  101 . 
         [0028]    Upon installation of this assembly, a female pin connection socket  113  of  FIG. 1  is inserted into the electrical connector mandrel  103  seating on shoulder  114  and provides O-rings  115  around its exterior distal end to seal against the interior of the electrical connector mandrel  103 . The stripped end  119  of the electrical cables  121  from the ESP are inserted into the male pin connector sleeve  118  from below, and affixed therein by set screws  118 ′ in this embodiment, and can compressively engage on contact bands  116  on the interior of the female connector sleeve or pin connection socket  113 . The electrical cable is stripped to a distance at  120  to seat the pin connection sleeve  118 . The pin connection sleeve  118  could alternatively be attached to the electrical cable  121  by crimping over the stripped end of the electrical cable  119 . The female pin connection socket  113  is retained within the electrical connector mandrel  103  by snap ring  117 , which is inserted upon installation into a circular groove  130  formed on the interior of the electrical connector mandrel  103 . The mini-mandrel or feed through assembly  105  is filled with epoxy  126  thereby sealing the upper portion of the feed through assembly  105 . If the electrical conductors or their shielded cable are separated from the wellhead hanger  101 , this female pin connection socket  113  would allow the cabling to separate and freely disconnect and drop away from the wellhead hanger  101  without opening the wellhead hanger  101  to the internal well pressure. Since the connector is confined within the electrical connector mandrel  103 , there is no chance of escape of well fluids under potential high pressure. 
         [0029]      FIG. 1 b    is an exploded view of the embodiment described above. The wellhead hanger body  101  provides a distinct shoulder  104  permitting the electrical connector mandrel  103  to be inserted until it seats against the shoulder  104 . The female pin socket  113  is attached to the stripped end of the surface cable  111 ′ in a manner not shown herein but could be by crimping, set screws, welding or the like because these pig tails can be assembled off site. A slot or groove.  131  allows a dielectric silicone grease, such as Dow Corning® DC 111, to be installed over the male pin  118  prior to insertion in the female pin connection socket  113 . Wear or contact bands  116  are more clearly depicted in this view and allow the male pin  118  to seat in the female pin connection socket  113 . This connection is made with little or no electrical resistance despite having a thick layer of dielectric grease smeared over the male pin  118  prior to insertion in the female pin socket  113 . All of the other features shown in  FIG. 1 b    are identical to those shown and described in  FIG. 1 . 
         [0030]      FIG. 2  is a modified embodiment of the present invention showing an electrical connector mandrel  203  compressively seated in a wellhead hanger recess  202 . Each electrical conductor can also inserted in an elastomeric seal (not shown) on an interior surface of a seal sub (not shown), all in a manner well known in this art. 
         [0031]    All of the described embodiments, shown in  FIGS. 1-5 and 7  provide similar elements and are installed in a similar manner. For example,  FIG. 2 a    is an exploded view of the structure shown in  FIG. 2  showing the stainless steel collar  204 , creating an interior shoulder  205  provided to prevent extrusion of the PEEK internal electrical mandrel  203  in high temperature, high pressure well situations; the threading  206  on the exterior end of the electrical mandrel  203  for connection to a well head device such as a seal sub (not shown in this view), and more clearly shows the wear bands  116  on the interior of the female pin socket  113 . 
         [0032]    Similarly,  FIG. 3A  is an exploded view of the structure shown in  FIG. 3  that shows the seal sub  307  connected to the threaded end of the internal electrical mandrel  203  and seated within the groove on the wellhead hanger  201 . The upper portion of each electrical conductor  121  extending from the ESP cable through the mini-mandrel or feed through assembly  105  to the surface is stripped at its proximal end  119  for insertion in a male pin connector sleeve assembly  118  which is inserted into the female pin socket  113 , and the entire assembly is moved into the internal electrical connector mandrel  103 ,  203 , while the stripped end of an exterior cable having a male socket pin  118 , attached on the stripped end  119  of the conductor  121 , is moved into the electrical connector mandrel  103 ,  203 , to seat within the female pin socket  113 . Both the male connector pin socket  118  and the female pin connector socket  113  are attached, such as by crimping the exposed end of the conductor on the interior of each respective pin socket. The preferred method for connection of both the male and female socket is by set screws. 
         [0033]    Finally,  FIG. 4 a    shows an exploded view of the structure of  FIG. 4  showing the seal sub  407  threaded both internally and externally for seating the sub in the wellhead hanger with threads  409  and the internal threads connecting to the threaded end of the internal electrical mandrel  206 . 
         [0034]    Dielectric grease, such as Dow Corning Corporation&#39;s DC 111, coats the exterior of the insulation of the electric conductor cable  118 , to prevent ingress of fluids which might short the electrical connection between the male and female sockets. The same dielectric grease can be used to coat the upper electrical conductor set  111 ,  111 ′ as they enter the exterior of the wellhead hanger through the seal subs  307 ,  407  in  FIGS. 3-4 , thereby preventing water or contaminants from reaching the socket connection on the interior of the electrical connector mandrel. 
         [0035]    Upon separation of the production tubing from below the wellhead hanger, the mini-mandrel or feed through assembly  105 , in each figure would drop away from the electrical connector mandrel  103 ,  203  as shown more specifically in  FIGS. 1-5 and 7  removing the electrical cable  119  in its insulation  121  and disconnecting the pin connection sleeve  118 , from the female pin socket  113 , that remains sealed within the wellhead hanger  101  thereby preventing the egress of high pressure fluids up the interior of the wellhead hanger  101 ,  201 ,  401 ,  601 . 
         [0036]    Each of the embodiments shown herein is structurally similar. Only changes in the wellhead hanger are made to accommodate the needs of the particular application of this invention. For example,  FIG. 1  describes the electrical connector mandrel  103  inserted in the wellhead hanger  101  as seated on a shoulder  104  on said wellhead hanger  101 . This design is modified in  FIGS. 2, 3 and 4  to provide a stainless steel collar  204  which provides a broader shoulder  205  to inhibit extrusion of the PEEK material from which the electrical connector mandrel  203  is formed when experience excessive pressure from the well bore (not shown).  FIGS. 2, 3 and 4  also disclose a space  213 ,  313  formed between the exterior of the electrical connector mandrel  203  and the interior surface of the wellhead hanger  201 . 
         [0037]      FIG. 5  describes the remaining seal left in the wellhead retaining the PEEK mandrel  203  after separation of the mini-mandrel or feed through assembly  105  from the wellhead. 
         [0038]      FIG. 6  is a closer cross-sectional view of the male pin assembly  118  which provides a longitudinal groove or slot  131  permitting an excess of a dielectric grease such as DC 111 to be extruded from the female socket  113  attached to the stripped end  111 ′ of electrical conductor  111 . Male pin  118  is connected to stripped electrical conductor  119  by set screws  118 ′, but could be attached by other means such as crimping or the like. 
         [0039]    Similarly, another embodiment can allow connection of the disconnectable assembly to a canned pump coupling as shown in  FIG. 7 , which functions in the same manner as the previously discussed embodiments. The feed-through assembly  105  is inserted into a dummy wellhead mandrel  703  threaded into the wellhead from above and connecting with threads  707 . The dummy mandrel seals in the wellhead with O-rings  705 . The canned pump coupler  730  is connected to the conductors emerging from the PEEK mandrel assembly  103  providing a threaded upper end  736  for attachment to the retaining sleeve  738 . Dielectric grease  734  is inserted between the top of the PEEK mandrel  103  and the bottom of a trash seal  732  through which each of the three conductors are guided into the canned pump coupler  730 . In all other respects, this embodiment functions in the same manner as the previous embodiments. The PEEK mandrel  103  seats against the internal shoulder  715  retaining the pressure seal at the wellhead even if the conductors separate and fall back into the well. 
         [0040]      FIG. 8  is an exploded view of the embodiment described in  FIG. 7 . Wellhead  701  is constructed with a feed through assembly  105  which, along with the PEEK mandrel  103 , is inserted into the dummy mandrel  703  and then screwed into the interior threads of the wellhead  707   a . Retaining sleeve  738  contains the trash seal  732  and is filled with dielectric grease to prevent the entry of water or dirt into the top of the wellhead pressure preserving penetrator of the present invention. The canned pump coupler  730  is connected to the retaining sleeve  738   
         [0041]    Each of the alternative disclosed herein derive from a common structure and are variations of the disclosure made herein. Other alternatives can be fashioned from a similar disclosure without departing from the spirit or intent of this invention. 
         [0042]    The accompanying drawings and description referred to herein are illustrative of the invention but not restrictive thereof and together with the description serve only to explain the principles of the invention claimed herein.