Wireline packoff for a downhole electrical tool

Abstract

A method and apparatus is provided for hermetic sealing of a wireline and a termination housing. The primary electrical connection of a wireline termination is sealed within a fluid-filed packoff bore of a termination housing. Wireline release strength can be selected upon wireline connection. A sealed termination housing has an uphole mechanical structure or support for transferring wireline armor tensile loads to the sub, a packoff bore for housing the wireline electrical conductor at a primary electrical connection, and a downhole closure. An inherent leak path of pressurized well fluids into termination housing is blocked by a dielectric fluid pad therein that fills the packoff bore from the downhole closure end and to a location at or uphole of the electrical connection made between the wireline and a hermetically sealed electrical connection exiting the downhole closure.

Embodiments of the invention for which and exclusive property or privilege is claimed is defined as follows: 
     
         1 . A cable head termination sub located between a wireline having wireline armor and an electrical conductor therealong, and a downhole tool, the termination sub comprising:
 a cable head having a structural body, the body having a packoff bore extending therethrough from an uphole end of the body to a downhole end of the body, the downhole end adapted for releasable coupling with the tool; and   the packoff bore configured to releasably receive a packoff assembly therein and having an uphole stop defining an entrance bore, and a downhole opening, the entrance bore having an entrance diameter smaller than a bore diameter of the packoff bore and sized for receiving the wireline therethrough;   a closure plug for sealing the downhole opening and fluidly isolating the packoff bore from the downhole tool; and   a grease port located on the body for introduction of dielectric grease to the packoff bore; and wherein   the packoff assembly comprises
 an uphole anchor slip having a slip bore for receiving the wireline therethrough and a slip interface for securing the wireline armor thereto, the anchor slip bearing against the uphole stop; 
 a packoff bushing downhole of the anchor slip having a bushing bore for receiving the wireline therethrough; 
 a boot contact attached to the wireline conductor to form a primary electrical connection; and 
 a feed-through connector having a first contact compatible with the boot contact and coupled thereto to form a secondary electrical connection, and a second contact for electrical connection with the downhole tool; and 
   when the packoff assembly is sealed within the packoff bore with the closure plug, the grease within the packoff bore prevents fluid from reaching the first and second electrical connections.   
     
     
         2 . The termination sub of  claim 1 , wherein the grease port directs grease to the downhole end of the packoff bore for backfilling the packoff bore with the grease from the downhole end toward the uphole end. 
     
     
         3 . The termination sub of  claim 1 , wherein the packoff assembly first comprises a boot housing having a downhole end sealably supporting the secondary electrical connection at the closure plug, an uphole end for receiving the primary electrical connection, and a boot having an uphole boot end fit concentrically about the wireline conductor and the boot contact and a downhole boot end for releasably receiving the first contact when the first contact is coupled with the boot contact, the boot residing within the boot housing. 
     
     
         4 . The termination sub of  claim 3 , wherein the boot housing has at least a first grease gallery adapted to direct injected grease from the grease port at least downhole to the downhole end of the packoff bore. 
     
     
         5 . The termination sub of  claim 3 , wherein the boot housing further comprises a circumferential seal for creating a seal with the packoff bore uphole of the grease port for preventing grease from travelling uphole between the boot housing and packoff bore. 
     
     
         6 . The termination sub of  claim 3 , wherein the boot housing has at least a second uphole gallery adapted to direct grease toward the uphole end of the packoff bore and along an annulus defined between the packoff assembly and the packoff bore. 
     
     
         7 . The termination sub of  claim 6 , wherein the boot housing further comprises an uphole port for discharging grease along the annulus. 
     
     
         8 . The termination sub of  claim 1 , wherein the uphole stop is removably coupled with the packoff bore. 
     
     
         9 . A method of sealing a wireline in a cable head located between the wireline and a downhole tool, the wireline having wireline armor and an electrical conductor therealong, the method comprising:
 inserting the wireline through an uphole stop of a packoff bore of the cable head and out of a downhole opening of the packoff bore;   positioning an anchor slip about the wireline;   bending one or more wires of the armor over a slip interface of the anchor slip and securing the one or more wires to the anchor slip;   positioning a packoff bushing about the wireline downhole of the anchor slip;   electrically connecting the conductor of the wireline with a boot contact to form a primary electrical connection;   coupling a first contact of a feed-through connector with the boot contact to form a secondary electrical connection;   inserting the first electrical and second electrical connections into a boot housing, the anchor slip, packoff bushing, and boot housing forming a packoff assembly;   inserting the packoff assembly into the packoff bore;   sealing the downhole opening of the packoff bore with a closure nut; and   introducing grease to the packoff bore such that grease fills the packoff bore from the downhole end to encompass at least the primary electrical connection and the secondary electrical connection.   
     
     
         10 . The method of  claim 9 , further comprising the step of securing the uphole stop within the packoff bore. 
     
     
         11 . The method of  claim 9 , wherein the step of introducing grease to the packoff bore further comprises directing the grease first to a downhole end of the packoff bore and then toward an uphole end of the packoff bore. 
     
     
         12 . The method of  claim 9 , further comprising the step of applying grease to one of the anchor slip, packoff bushing, and boot housing, or a combination thereof, prior to sealing the downhole opening of the packoff bore. 
     
     
         13 . The method of  claim 9 , wherein the step of inserting the first and second electrical connections into a boot housing further comprises inserting the first and second electrical connections into a boot and inserting the boot into the boot housing. 
     
     
         14 . The method of  claim 9 , wherein the step of positioning the anchor slip further comprises securing a vise to the wireline downhole of the downhole opening and coupling the anchor slip to the vise, and step of inserting the packoff assembly into the packoff bore comprises first removing the vise from the wireline. 
     
     
         15 . The method of  claim 9 , wherein grease is introduced to the downhole end of the packoff bore. 
     
     
         16 . The method of  claim 9 , wherein the grease is introduced at an axial location uphole of the downhole end of the packoff bore, the grease flowing toward the downhole end via at least a first grease gallery. 
     
     
         17 . The method of  claim 16 , further comprising directing the grease toward the uphole end from the downhole end via at least a second grease gallery. 
     
     
         18 . A packoff assembly for use within a packoff bore of a cable head to connect a wireline having wireline armor and an electrical conductor therealong with a downhole tool, comprising:
 an uphole anchor slip having a slip bore for receiving the wireline therethrough and a slip interface for securing the wireline armor thereto;   a packoff bushing having a bushing bore for receiving the wireline therethrough;   a boot housing having a feed-through connector sealably supported therein, the feed-through connector having a first contact compatible with a boot contact attached to the wireline conductor and a second contact for electrical connection with the downhole tool; and   at least a first grease gallery formed in the boot housing and adapted to receive grease injected into the packoff bore and directed the grease towards a downhole end of the boot housing.   
     
     
         19 . The packoff assembly of  claim 18 , wherein the boot housing defines an uphole port in communication with at least a second grease gallery and adapted to direct grease toward an uphole end of the packoff bore and along an annulus defined between the packoff assembly and the packoff bore. 
     
     
         20 . The packoff assembly of  claim 18 , wherein the boot housing comprises a boot having an uphole boot end fit concentrically about the wireline conductor and the boot contact a downhole boot end for releasably receiving the first contact when the first contact is coupled with the boot contact, the boot residing within the boot housing.