Removing a casing section in a wellbore

A method, for plugging a cased wellbore, comprising:

• running a downhole tool into a wellbore in a formation, the wellbore being at least partially lined with a length of casing and an annulus surrounding the casing at least partially filled with cement;
• the downhole tool including at least one sensor, the at least one sensor including a sensor for determining a quality of the cement in the annulus;
• determining, using the sensor for determining the quality of the cement, whether the quality of the cement in the annulus along an axial section of the casing having a length less than the length of the casing satisfies a predetermined standard;
• if the quality of the cement along the axial section satisfies a predetermined standard, performing a removal operation on the axial section of the casing without removing the cement within the annulus along the axial section;
• otherwise, performing a removal operation on the axial section of the casing and at least a portion of the cement in the annulus along the axial section of the casing;
• and
• forming a plug at least partially where the axial section of the casing was removed, p1 wherein the at least one sensor includes a second sensor, and wherein the method further comprises, after completing the removal operation on the axial section of casing, determining with the second sensor whether any of the axial section of the casing remains adhered to the cement.

A method for abandoning a wellbore, comprising:

• running a downhole cutting tool into a wellbore in a formation, the wellbore having a casing and an annulus between the outer wall of the casing and the formation, the annulus being at least partially filled with cement, the downhole cutting tool includes a cutting element including at least one of a laser, plasma cutter, or abrasive jet;
• using one or more sensors to locate a section along the length of the wellbore in which a quality of the cement in the annulus meets a predetermined standard;
• using the cutting tool to cut an axial section of the casing in the section along the length of the wellbore in which the quality of the cement in the annulus meets the predetermined standard;
• using one or more sensors, determining that one or more segments of casing remain adhered to cement within the axial section of casing;
• after cutting the axial section of casing and determining that the one or more segments of casing remain, removing the one or more segments of casing using one or more casing removal tools;
• forming a plug in the wellbore, the plug being formed at least partially
• where the axial section of casing was cut;
• cutting a completion assembly with the cutting tool to separate the completion assembly into first and second segments, wherein the completion assembly is positioned radially-outward from the downhole cutting tool and radially-inward of the casing:
• pumping a stream of fluid radially-outward through an opening in the downhole cutting tool, the cutting element extending at least partially through the stream during cutting;
• and
• removing at least a portion of the cement proximate to where the axial section of the casing was cut, using an underreamer.