Coupling apparatus for connecting two drill pipe sections and a method of using same

A method of providing a controllable weak connection in a drill string arranged to be in a locked-to-bottom mode, the method comprising:

• arranging a coupling apparatus for connecting two drill-pipe sections in a string of drill-pipe sections joined together by tool joints, the coupling apparatus comprising:
• a first pipe with a first end portion and a second end portion, the first end portion being provided with a tool joint for connection to a drill-pipe section;
• and
• a second pipe with a first end portion and a second end portion, the first end portion being provided with a tool joint for connection to a drill-pipe section;
• each of the second end portions of the pipes further being provided with a flange provided with at least two spaced-apart bores which are each arranged to receive a bolt so that the flanges and the bolts form a flange connection configured to hold the first pipe and the second pipe fixed against axial movement relative to each other, wherein each of the first pipe and the second pipe is provided with a mutual engagement means configured to prevent relative rotation thereof, wherein the bolts are axial tension bolts subjected to axial forces only and are configured to rupture on a predetermined axial load;
• wherein the second end portion of one of the pipes is provided with a female portion for receiving a complementarily adapted male portion arranged in the second end portion of the other one of the pipes, and wherein the female portion and the male portion are arranged for axial displacement relative to each other;
• and
• wherein a predetermined axial-load-carrying capacity of the coupling apparatus is provided by the bolts connecting the flanges arranged on the first pipe and the second pipe of the coupling apparatus;
• and
• fitting the coupling apparatus in a portion of the drill string.

A drill string including a coupling apparatus for connecting two drill-pipe sections in a string of drill-pipe sections joined together by tool joints, the coupling apparatus comprising:

• a first pipe with a first end portion and a second end portion, the first end portion being provided with a tool joint for connection to a drill-pipe section;
• a second pipe with a first end portion and a second end portion, the first end portion being provided with a tool joint for connection to a drill-pipe section;
• each of the second end portions of the pipes further being provided with a flange provided with at least two spaced-apart bores which are each arranged to receive a bolt so that the flanges and the bolts form a flange connection configured to hold the first pipe and the second pipe fixed against axial movement relative to each other, wherein each of the first pipe and the second pipe is provided with a mutual engagement means configured to prevent relative rotation thereof, and that the bolts are axial tension bolts subjected to axial forces only, the bolts configured to rupture on a predetermined axial load;
• wherein the second end portion of one of the pipes is provided with a female portion for receiving a complementarily adapted male portion arranged in the second end portion of the other one of the pipes, and wherein the female portion and the male portion are arranged for axial displacement relative to each other.