Systems and methods for releasing a tool string

A method of separating a tool string, comprising:

• securing a separation bolt against removal from a bore with a separation bolt retainer coupled to a bolt housing, the separation bolt retainer having one or more mechanical fasteners that couples the separation bolt retainer to the bolt housing and secures the separation bolt against removal from the bore and launching itself upwards during operation;
• conveying the tool string into a wellbore, the tool string including a release tool having a main body surrounding the separation bolt retainer and at least partially surrounding the bolt housing and coupled to the bolt housing, the bolt housing defines the bore configured to receive a separation bolt therein, the separation bolt being configured with at least one explosive charge;
• activating an electrically responsive trigger mechanism arranged within the release tool, the trigger mechanism being electrically coupled to the separation bolt;
• sending a signal to the separation bolt with the trigger mechanism;
• and
• breaking the separation bolt into a first segment and a second segment upon receipt of the signal and thereby freeing a lower sub from a bottom end of the bolt housing,
• wherein the separation bolt is a pyrotechnic fastener having one or more explosive charges arranged therein and breaking the separation bolt comprises detonating the one or more explosive charges upon receipt of the signal,
• wherein the separation bolt comprises a score line about a circumference of the separation bolt at an intermediate location along a length of the separation bolt indicating a location where the separation bolt severs in response to the detonation of the at least one charge to provide a controlled release point between the first and second segments and allow subsequent use of at least the second segment of the separation bolt in the lower sub;
• wherein the bore is a first bore and the lower sub defines a second bore configured to be arranged coaxial with the first bore for mutual receipt of the separation bolt.

A tool string, comprising:

• a rope socket operatively coupled to a conveyance;
• a release tool coupled to the rope socket and having a main body surrounding a separation bolt retainer, at least partially surrounding a bolt housing, and coupled to the bolt housing, the bolt housing defines a bore configured to receive a separation bolt therein and an electrically responsive trigger mechanism electrically coupled to the separation bolt;
• the separation bolt retainer having one or more mechanical fasteners coupled to the bolt housing and configured to secure the separation bolt against removal from the bore and launching itself upwards during operation;
• and
• a lower sub coupled to a bottom end of the bolt housing with the separation bolt, wherein the trigger mechanism is configured to send a signal to the separation bolt to detonate one or more explosive charges arranged within the separation bolt and thereby allowing the release tool to separate from the lower sub,
• wherein the separation bolt is a pyrotechnic fastener having one or more explosive charges arranged therein and breaking the separation bolt comprises detonating the one or more explosive charges upon receipt of the signal,
• wherein the separation bolt comprises a score line about a circumference of the separation bolt at an intermediate location along a length of the separation bolt indicating a location where the separation bolt severs into first and second segments in response to the detonation of the at least one charge, wherein the separation bolt is severed at the score line to provide a controlled release point between the first and second segments and allow subsequent use of at least the second segment of the separation bolt in the lower sub;
• wherein the separation bolt is configured with at least one explosive charge;
• wherein the bore is a first bore and the lower sub defines a second bore configured to be arranged coaxial with the first bore for mutual receipt of the separation bolt.