In the beginning of the story, he used a phony ID to work as an engineer in a project that tried to drill through the oceanic crust to reach mantle. Some organization tried to sabotage the project.
The computer was definitely 1960s or 1970s since they still used punched cards for data input.
This could well be a novella by Roger Zelazny entitled The Eve of RUMOKO, first published in 1969.
The protagonist has erased his identity, and has taken the name "Albert Schweitzer". The RUMOKO project is an attempt to drill into the Earth's mantle to create more living space using "shaped nuclear charges"- a review from goodreads describes it as:
A project to drill into the mantle near Iceland called RUMOKO is being sabotaged and a fixer-for-hire going by the pseudonym Albert Schweitzer is hired to stop them. The project is supposed to create new lands but the saboteurs are worried about creating seafloor earthquakes which threaten colonies there. At the pointy end of the mission Albert suspects he may be on the wrong side.
As the OP recalled, the compute data was indeed stored on punched cards:
...he rose from his chair, crossed the room, opened a file cabinet He rummaged around in it for a time, then returned holding a sheaf of punchcards like a poker hand. He dropped them onto the desk in front of me.
"That's you," he said.
