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An apparatus for protecting equipment in a wellhead from exposure to fluid pressures, abrasives and corrosive fluids used in a well treatment to stimulate production, includes a mandrel to be inserted through the wellhead into an operative position. The apparatus further includes injectors for recip

An apparatus for protecting equipment in a wellhead from exposure to fluid pressures, abrasives and corrosive fluids used in a well treatment to stimulate production, includes a mandrel to be inserted through the wellhead into an operative position. The apparatus further includes injectors for reciprocating the mandrel to and from the operative position. The injectors are connected on their top ends to a connector plate that provides a support platform to permit equipment, such as blowout preventers, wireline units, coil tubing injectors or the like, to be mounted to the top of the apparatus.

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1. An apparatus for protecting equipment in a wellhead of a well from exposure to fluid pressures, abrasives and corrosive fluids used in a well treatment to stimulate production, comprising:a tool adapted to be inserted through the wellhead of the wellhead into an operative position, the tool inclu

1. An apparatus for protecting equipment in a wellhead of a well from exposure to fluid pressures, abrasives and corrosive fluids used in a well treatment to stimulate production, comprising:a tool adapted to be inserted through the wellhead of the wellhead into an operative position, the tool including a base plate adapted to be connected to a top end of the wellhead and a connector plate at a top end thereof for supporting equipment selectively mounted to the tool; anda pair of injectors in a parallel relationship located at respective opposed sides of the base plate and connector plate, each injector having opposed ends secured to the base plate and the connector plate, respectively, so that the injectors can reciprocate a mandrel of the tool through the wellhead into and out of the operative position when the base plate is connected to the top end of the wellhead. 2. An apparatus as claimed in claim 1 wherein the injectors comprise a pair of hydraulic cylinders, each including a cylinder and a piston rod extendable from the cylinder and thereby forming a cylinder end and a rod end of the injector, the cylinder end being secured to a bottom of the connector plate, and the rod being connected to the base plate. 3. An apparatus as claimed in claim 2 wherein the tool comprises a mandrel adapted to be inserted down through the wellhead into the operative position, the mandrel including an annular sealing body secured to a bottom end thereof for sealing engagement within a tubing head spool above a bit guide at a top of a casing of the well when the mandrel is in the operative position. 4. An apparatus as claimed in claim 3 wherein the tool further comprises a mandrel head connected to a top end of the mandrel, the mandrel head including a passage that extends therethrough and is in fluid communication with the mandrel, the mandrel head being releasably secured to the base plate when the mandrel is inserted through the wellhead into the operative position. 5. An apparatus as claimed in claim 4 wherein the tool further comprises a high pressure valve mounted to the mandrel head and in fluid communication with the passage through the mandrel head. 6. An apparatus as claimed in claim 5 wherein the tool further comprises an adapter spool mounted to a top of the high pressure valve, the adapter spool having a central passage in fluid communication with the high pressure valve, the adapter spool being secured to the connector plate to permit equipment to be selectively mounted to a top of the apparatus. 7. An apparatus as claimed in claim 6 further comprising a fracturing head mounted between the high pressure valve and the mandrel head, the fracturing head including an axial passage in fluid communication with the mandrel and the high pressure valve, and at least one radial passage in fluid communication with the axial passage. 8. An apparatus as claimed in claim 6 further comprising a fracturing head mounted between the high pressure valve and the adapter spool, the fracturing head including an axial passage in fluid communication with the mandrel and the high pressure valve, and at least one radial passage in fluid communication with the axial passage. 9. An apparatus as claimed in claim 1 wherein the base plate comprises a fluid seal in a passage extending therethrough, through which the mandrel is reciprocally movable. 10. An apparatus as claimed in claim 9 wherein the base plate further comprises a bleed valve for selectively closing a bleed port in fluid communication with the passage of through the base plate. 11. An apparatus as claimed in claim 4 wherein the mandrel head comprises a lock nut around the mandrel that may selectively be connected to a threaded connector on the base plate, to lock the mandrel in the operative position. 12. An apparatus as claimed in claim 3 wherein the annular sealing body comprises at least one O-ring to seal a gap between the annular sealing body and an interior wall of the tubing head spool. 13. An apparatus as claimed in claim 3 wherein the annular sealing body comprises a bottom end contoured for abutting the bit guide. 14. A method for protecting equipment in a wellhead of a well from exposure to fluid pressures, abrasives and corrosive fluids used in a well treatment to stimulate production of the well, comprising steps of:a) suspending above wellhead of the well an apparatus which includes a tool having a mandrel adapted to be inserted through the wellhead to an operative position, the tool including a base plate adapted to be connected to a top end of the wellhead and a connector plate at a top end of the apparatus, and which further includes a pair of injectors mounted in a parallel relationship on opposed sides of the apparatus, each injector having opposed ends secured to the base plate and the connector plate, respectively;b) aligning the mandrel with the wellhead and lowering the apparatus until the apparatus rests on the wellhead, and mounting the base plate to the wellhead;c) opening a fluid flow control mechanism of the wellhead to permit access to a well bore;d) actuating the injectors to insert the mandrel through the wellhead into the operative position in which an annular sealing body at a bottom end of the mandrel is in a fluid sealing engagement with an inner wall of a tubing head spool at a top of a casing of the well;e) locking the mandrel in the operative position; andf) connecting the apparatus to a high pressure fluid line for well stimulation. 15. A method as claimed in claim 14 wherein the high pressure fluid line is connected to a high pressure valve which is in fluid communication with the mandrel and suspended from the connector plate. 16. A method as claimed in claim 14 comprising a further step of equalizing fluid pressure across the fluid flow control mechanism of the wellhead prior to step (c). 17. A method of running a tubing string into a well while protecting equipment in a wellhead of the well from exposure to fluid pressures, abrasives and corrosive fluids used in a well treatment or well service, comprising steps of:a) mounting to wellhead of the well a base plate of an apparatus, the apparatus including a tool having a mandrel adapted to be inserted through a the wellhead to an operative position, the tool further including a fracturing head having an axial passage and at least one radial passage in fluid communication with the axial passage, a high pressure valve mounted to the fracturing head and a connector plate connected to a top of the high pressure valve, and the apparatus further including a pair of injectors located in a parallel relationship on opposed sides of the apparatus, each injector having opposed ends respectively secured to the base plate and the connector plate;b) aligning the mandrel with the wellhead and lowering the apparatus until the apparatus rests on the wellhead, and mounting the base plate to the wellhead;c) opening a fluid flow control mechanism of the wellhead to permit access to a well bore of the well;d) actuating the injectors to insert the mandrel through the wellhead into the operative position in which an annular sealing body at a bottom end of the mandrel is in a fluid sealing engagement with an inner wall of a tubing head spool of the wellhead;e) locking the mandrel in the operative position; andf) running the tubing string into the wellbore through at least one blowout preventer mounted to the connector plate. 18. A method as claimed in claim 17 further comprising steps, prior to step (f), of positioning the at least one blowout preventer above the connector plate and connecting the at least one blowout preventer in a fluid tight seal to the connector plate. 19. A method as claimed in claim 18 wherein the tubing string is a coil tubing string and is injected into the well using a coil tubing injector. 20. A method as claimed in claim 19 further comprising a step of mounting the coil tubing injector to a top of the blowout preventer. 21. A method as claimed in claim 17 further comprising a step of equalizing fluid pressure across the fluid flow control mechanism of the wellhead prior to step (c).