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A blowout preventer (BOP) protector is adapted to support a tubing string in a wellbore so that the tubing string is directly accessible during a well treatment to stimulate production. The BOP protector includes a mandrel having a sealing assembly mounted to its bottom end for pack-off in a casing

A blowout preventer (BOP) protector is adapted to support a tubing string in a wellbore so that the tubing string is directly accessible during a well treatment to stimulate production. The BOP protector includes a mandrel having a sealing assembly mounted to its bottom end for pack-off in a casing of a well to be stimulated. The mandrel is connected at its top end to a fracturing head, including a central passage and radial passages in fluid communication with the central passage. The mandrel is locked in a fixed position by a lockdown nut that prevents upward movement induced by fluid pressures in the wellbore. The advantages are that the BOP protector permits access to the tubing string during well treatment and enables an operator to move the tubing string up and down or run coil tubing into or out of the wellbore without removing the tool. This reduces operation costs, saves time and enables many new procedures that were previously impossible or impractical.

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1. An apparatus for protecting a blowout preventer mounted to a wellhead from exposure to fluid pressures, abrasives and corrosive fluids used in a well treatment to stimulate production, and for supporting a tubing string in a wellbore so that the tubing string is accessible during the well treatme

1. An apparatus for protecting a blowout preventer mounted to a wellhead from exposure to fluid pressures, abrasives and corrosive fluids used in a well treatment to stimulate production, and for supporting a tubing string in a wellbore so that the tubing string is accessible during the well treatment, the apparatus including a mandrel adapted to be inserted down through the blowout preventer to an operative position, comprising:a base member adapted for connection to the wellhead, the base member including fluid seals through which the mandrel is reciprocally movable;a fracturing head including a central passage in fluid communication with the mandrel and at least one radial passage in fluid communication with the central passage;a tubing adapter mounted to a top end of the fracturing head, the tubing adapter supporting the tubing string while permitting fluid communication with the tubing string;a sealing assembly attached to a bottom end of the mandrel to seal an annulus between the mandrel and a casing of the well when the mandrel is in the operative position; anda lock mechanism for locking the apparatus in the operative position to inhibit upward movement of the mandrel induced by fluid pressures in the wellbore. 2. An apparatus as claimed in claim 1 wherein the tubing adapter comprises a first threaded connector to permit connection of the tubing string so that the tubing string is suspended from the tubing adapter, and a second connector to permit connection of a high pressure valve to permit fluids to be pumped through the tubing string. 3. An apparatus as claimed in claim 1 wherein the tubing adapter comprises a flange through which coil tubing can be run into the well and a blowout preventer is mounted to the tubing adapter to seal around the coil tubing and contain fluid pressure within the wellbore. 4. An apparatus as claimed in claim 1 wherein the lock mechanism comprises a mechanical lockdown mechanism including a spiral thread on the base member engaged by a complementary thread of a lockdown nut. 5. An apparatus as claimed in claim 1 wherein the sealing assembly comprises an annular cup, the annular cup being adapted to provide a high pressure fluid seal in the annulus when fluids used in a well treatment to stimulate production are pumped into the well. 6. An apparatus as claimed in claim 5 wherein the sealing assembly further includes a cup tool connected to a bottom end of the mandrel, the cup tool including a radial retainer shoulder adjacent a bottom end of the mandrel to retain the annular cup. 7. An apparatus as claimed in claim 6 wherein the annular cup comprises a steel ring bonded to an elastic cup so that an axial force is exerted against the elastic cup when the fluids are pumped into the well. 8. An apparatus as claimed in claim 7 wherein the annular cup further comprises an O-ring mounted in a groove in an inner surface of the steel ring to seal an annulus between the cup tool and the steel ring to which the elastic cup is bonded. 9. An apparatus as claimed in claim 1 wherein the apparatus further comprises a blast joint through which the tubing string is run to protect the tubing string from erosion when abrasive fluids are pumped through the at least one radial passage in the fracturing head. 10. An apparatus as claimed in claim 9 wherein the blast joint has a threaded top end that engages a complimentary thread on the tubing adapter. 11. A method of providing access to a tubing string while protecting at least one blowout preventer on a wellhead from exposure to fluid pressure, abrasive and corrosive fluids during a well treatment to stimulate production, comprising the steps of sequentially:a) suspending an apparatus above the wellhead, the apparatus comprising a mandrel having a mandrel top end and a mandrel bottom end that includes an annular sealing assembly, a fracturing head mounted to the mandrel top end, the fracturing head having an axial passage in fluid communication with the mandr el and at least one radial passage in fluid communication with the axial passage, and a base member for detachably securing the mandrel to the wellhead;b) aligning the apparatus with a tubing string supported on the wellhead and extending above the wellhead, and lowering the apparatus until a top end of the tubing string extends through the axial passage above the fracturing head;c) connecting a tubing adapter to the top end of the tubing string, connecting the tubing adapter to a top end of the fracturing head, lowering the tubing string and the apparatus until the apparatus rests on the wellhead, and mounting the base member to the wellhead;d) opening the at least one blowout preventer, as required;e) stroking the mandrel through the wellhead into the casing of the well until the mandrel reaches an operative position in which the seal assembly is in sealing contact with an inner wall of the casing; andf) locking the fracturing head to inhibit the mandrel from upward movement induced by fluid pressure in the well. 12. A method as claimed in claim 11 wherein prior to performing step (a), the method further comprises a step of:pulling the tubing string and supporting tubing hanger from the wellhead and removing the tubing hanger, and further raising the tubing string until the tubing string is pulled out of the well to an extent that a length of the tubing string above the wellhead exceeds a length of the apparatus for protecting the blowout preventer, and supporting the tubing string at the wellhead. 13. A method as claimed in claim 12, further comprising a step of:mounting at least one high-pressure valve to the tubing adapter in operative fluid communication with the tubing string. 14. A method as claimed in claim 11 wherein after step (c) and prior to step (d) the method further comprises a step of equalizing fluid pressure across the at least one blowout preventer. 15. A method as claimed in claim 11 further comprising a step of utilizing the tubing string as a dead string to measure downhole pressure during the well stimulation treatment. 16. A method as claimed in claim 11 further comprising a step of utilizing the tubing string to pump well stimulation fluids into the well during the well stimulation treatment. 17. A method as claimed in claim 16 further comprising a step of utilizing the tubing string in combination with the at least one radial passage in the fracturing head to pump well stimulation fluids down into the well. 18. A method as claimed in claim 11 further comprising a step of utilizing the tubing string as a well evacuation string in the event of a screen-out, so that fluids can be pumped down the annulus of the casing and up the tubing string to clean and circulate proppants out of the wellbore. 19. A method as claimed in claim 11 further comprising a step of pumping a first fluid down the tubing string and pumping a different, second fluid down the annulus of the well, so that the first and second fluids co-mingle in the well. 20. A method as claimed in claim 11 wherein the tubing string is used for spotting acid in the well, and the method further comprises steps of:setting a first plug in the well below a lower end of the tubing string, if required, to define a lower limit of an area to be acidized; andpumping acid down the tubing string to treat a portion of the wellbore above the first plug. 21. A method as claimed in claim 20 further comprising steps of setting a second plug in an area above the first plug to define an upper limit of the area to be acidized, and pumping acid under pressure through the tubing string into the area to be acidized. 22. A method of running a tubing string into or out of a well while protecting at least one blowout preventer on a wellhead during a well treatment to stimulate production, comprising steps of:a) mounting to the wellhead a base member of an apparatus for protecting the at least one blowout preventer during the well treatment, the apparatus comprising a mandr el having a mandrel top end and a mandrel bottom end that includes an annular sealing assembly, a fracturing head mounted to the mandrel top end, the fracturing head having an axial passage in fluid communication with the mandrel and at least one radial passage in fluid communication with the axial passage;b) closing a blowout preventer mounted to an adapter flange mounted to a top the fracturing head;c) opening the at least one blowout preventer on the wellhead, as required;d) stroking the mandrel bottom end down through the at least one blowout preventer and the wellhead into the casing until the mandrel is in an operative position in which the fracturing head rests against the base member and the annular sealing assembly is in fluid sealing engagement with an inner wall of the casing of the well;e) locking the mandrel in the operative position; andf) running the tubing string into or out of the well through the blowout preventer mounted to the adapter flange. 23. The method as claimed in claim 22 wherein the step of running the tubing string comprises a step of running a coil tubing string into or out of the well.