Method and apparatus for a joint-locking plug

A method comprising:

• deploying downhole a joint-locking plug on a toolstring into a tubing string including multiple tubing joints and containing well fluid,
• the joint-locking plug including:
• a cylindrical axis, whereby the cylindrical axis is a virtual axis of revolution for the joint-locking plug,
• an expandable gripping portion,
• whereby the expandable gripping portion includes at least one radial protrusion whereby the tubing joints are connected longitudinally to each other's while keeping a joint transition gap at the connection, the joint transition gap being positioned radially on the inner surface of the tubing string;
• positioning the toolstring, including the joint-locking plug, uphole of a selected joint transition gap;
• actuating the joint-locking plug by expanding the expandable gripping portion and contacting the at least one radial protrusion with the inner surface of the tubing string, uphole of the selected joint transition gap;
• pumping down the joint-locking plug up to the position where the at least one radial protrusion of the gripping portion is facing radially the selected joint transition gap;
• locking the at least one radial protrusion of the gripping portion radially inside the selected joint transition gap, so that the joint-locking plug is stopped from moving longitudinally downhole within the tubing string;
• retrieving the toolstring, keeping the joint-locking plug locked within the joint transition gap;
• positioning an untethered object on the joint-locking plug or closing a flapper valve on the joint-locking plug;
• performing a downhole operation.

A joint-locking plugging apparatus, for use inside a tubing string including multiple tubing joints and containing well fluid comprising:

• a joint transition gap,
• whereby the joint transition gap is created by connecting the tubing joints longitudinally to each other's and keeping a longitudinal and radial gap between the tubing joints on the inner surface of the tubing string;
• a joint-locking plug including:
• a cylindrical axis, whereby the cylindrical axis is a virtual axis of revolution for the joint-locking plug;
• an expandable gripping portion, including separate slips,
• wherein the separate slips include a protrusion section and an anchoring section on their outer face,
• wherein the protrusion section includes at least one protrusion,
• wherein the anchoring section is positioned longitudinally uphole compared to the protrusion section,
• wherein the separate slips include an inner surface which is flared, such as conical, spherical or combination thereof,
• wherein the inner surface of the separate slips comprises one average conical leading angle, relative to the cylindrical axis of the plug;
• a locking ring, including an outer surface,
• whereby the outer surface is flared, such as conical, spherical or combination thereof,
• whereby the outer surface comprises two longitudinally subsequent flared portions, wherein each of the two flared portions is characterized by an average conical leading angle, and wherein a first flared portion is characterized by a shallow conical leading angle and a second flared portion is characterized by a steep conical leading angle,
• whereby the shallow and steep leading angles have different values relative to the cylindrical axis of the plug, and the angular value difference between the steep and shallow leading angle is between 0.5 and 15 deg,
• whereby the relative position of the first flared portion is uphole compared to the second flared portion, within the locking ring,
• whereby the average conical leading angle of the inner surface of the slips equals the steep conical leading angle of the locking ring, within a tolerance of plus or minus 2 degrees, and is different from the shallow conical leading angle of the locking ring.