Well tool device for forming a permanent cap rock to cap rock barrier and method for using same

1. A well tool device for forming a permanent cap rock to cap rock barrier which seals against a reservoir in a well, the well tool device comprising:

a housing;

a movable partition device provided within the housing, the partition device separating an inner volume of the housing into a first volume defining a first compartment and a second volume defining a second compartment;

a pyrotechnic mixture configured to completely melt the well tool device and proximate surrounding materials to form the cap rock to cap rock barrier when solidifying, provided in the first compartment; and

a fluid line providing fluid communication between the second compartment and an outside of the housing by allowing fluids to enter the second compartment through the fluid line so as to continuously equalize a differential pressure between an inside of the second compartment and an ambient well bore pressure throughout an entirety of a lowering of the well tool device into the well.

2. The well tool device according to claim 1 , wherein the partition device is:

a piston;

a diaphragm; or

a bladder.

3. The well tool device according to claim 1 , wherein the well tool device further comprises:

a valve device providing fluid communication between the first compartment and the outside of the housing.

4. The well tool device according to claim 1 , wherein the first compartment is fluid tight.

5. The well tool device according to claim 1 , wherein the well tool device further comprises:

an ignition head provided within the first compartment, the ignition head being configured to ignite the pyrotechnic mixture.

6. A method for forming a permanent cap rock to cap rock barrier which seals against a reservoir in a well, using a well tool device, the well tool device comprising:

a housing;

a movable partition device provided within the housing, the partition device separating an inner volume of the housing into a first volume defining a first compartment and a second volume defining a second compartment;

a pyrotechnic mixture provided in the first compartment, the pyrotechnic mixture being configured to completely melt the well tool device and proximate surrounding materials; and

a fluid line providing fluid communication between the second compartment and an outside of the housing by allowing fluids to enter the second compartment through the fluid line so as to continuously equalize a differential pressure between an inside of the second compartment and an ambient well bore pressure during throughout an entirety of a lowering of the well tool device into the well;

wherein the method comprises:

while running the well tool device into the well, equalizing the differential pressure by allowing fluids to enter the second compartment through the fluid line;

while running the well tool device into the well, equalizing a pressure difference between a pressure inside the first compartment and a pressure inside the second compartment, by means of the partition device being affected by the pressure inside the second compartment;

installing the well tool device in the well;

igniting the pyrotechnic mixture thereby completely melting the well tool device and the proximate surrounding materials; and

waiting a period of time, thereby allowing the completely melted materials to solidify into a cap rock to cap rock barrier which seals against a reservoir in the well.

7. The method according to claim 6 , wherein the method further comprises:

assembling a plurality of well tool devices into one stack before the running of the well tool device into the well and the installing of the well tool device in the well.