Downhole Apparatus

An apparatus comprising:

• a downhole tool for connecting and selectively disconnecting within a wellbore first and second portions of a downhole tool string from each other, wherein the downhole tool comprises:
• a first connector sub connectable with the first portion of the downhole tool string;
• a second connector sub connectable with the second portion of the downhole tool string;
• an internal chamber;
• and
• a fastener connecting the first and second connector subs, wherein the fastener fluidly separates the internal chamber into a first chamber portion and a second chamber portion, wherein the first chamber portion is fluidly connected with a space external to the downhole tool, and wherein the downhole tool is selectively operable to disconnect the first and second connector subs from each other to disconnect the first and second portions of the downhole tool string from each other.

An apparatus comprising:

• a downhole tool for connecting and selectively disconnecting within a wellbore first and second portions of a downhole tool string from each other, wherein the downhole tool comprises:
• a first connector sub connectable with the first portion of the downhole tool string;
• a second connector sub connectable with the second portion of the downhole tool string, wherein the first and/or second connector subs at least partially define an internal chamber;
• and
• a fastener connecting the first and second connector subs and fluidly isolating the internal chamber from external space, wherein the fastener is separable into first and second fastener portions to disconnect the first and second connector subs and thereby disconnect the first and second portions of the downhole tool string from each other.

A method comprising:

• connecting a first connector sub of a downhole tool with a first portion of a downhole tool string and connecting a second connector sub of the downhole tool with a second portion of the downhole tool string to connect the first and second portions of the downhole tool string, wherein a fastener of the downhole tool connects the first and second connector subs;
• conveying the downhole tool string within a wellbore while the fastener blocks wellbore fluid from flowing into an internal chamber of the downhole tool;
• and
• operating the downhole tool to separate the fastener into first and second fastener portions thereby permitting the wellbore fluid to flow into the internal chamber to disconnect the first and second connector subs and thus disconnect the first and second portions of the downhole tool string from each other.