Thermite composition for a process of plugging and abandoning a petroleum well and process of plugging and abandoning a petroleum well using said thermite composition

A process of plugging and abandoning a petroleum well using a thermite composition, comprising the steps of:

• a) preparing the thermite composition, which comprises
• 1.1 a tube-sealing composition comprising:
• aluminium in an amount of 10-40 wt %, and
• a metal oxide in an amount of 60-90 wt %
• 1.2 a gas leakage-preventing composition comprising a metal with a melting point ranging from 100-300° C.,
• each component being mixed separately before arranging in a tubing;
• b) plugging a petroleum well to be plugged and abandoned with a mechanical bridge plug before introducing the thermite composition into it;
• c) layering the thermite composition prepared in step a) in a closed, hollow tubing, wherein the layering of the thermite composition provides the tube-sealing composition at the bottom, followed by the gas leakage-preventing composition, before introducing to the petroleum well to be plugged and abandoned;
• d) initiating an ignition to generate thermal energy, triggering a thermite reaction that causes metal melting for tube sealing and preventing gas leakage, wherein an explosion caused by said thermite reaction occurs on the lateral and lower sides.