In a brief story, offshore oil drillers strike a gusher of blood. It pulses out periodically as if they have pierced a giant subterranean heart. The ambience is Lovecraftian; clearly they have disturbed something that would better have been left alone. I may have read this story in an English-language anthology during the 1960s or 1970s.
The Night Sea-Maid Went Down by Brian Lumley.
Brian Lumley went through a phase of writing Lovecraftian stories, and indeed he was very good at it and I strongly recommend them to all fans of eldritch horror™. I read this one in his anthology Haggopian.
It's written in the form of a letter describing what happened on the oil rig Sea Maid drilling in the North Sea just off the coast near the city of Sunderland.
The story tells us:
We hadn’t drilled more than six-hundred feet into the sea-bed when we brought up that first star-shaped thing.
Then as they continue drilling their seismometers start picking up an odd sound:
Oh, the trouble was there all right, whatever it was, but it was showing up so regularly that we were fooled into believing the fault to be mechanical. On the seismograph it showed as a regular blip in an otherwise perfectly normal line; a blip that came up bang on time once every five seconds or so - blip … blip … blip - very odd!
Finally a freak storm starts rocking the rig and eventually destroys it killing most of the crew apart from our protagonist. But in the last few moments before the rig is destroyed:
But there, I’ve held off from telling the important part - and for the same reason Joe Borszowski held off: I don’t want to be thought a madman. Well, I’m not mad, Johnny, but I don’t suppose for a single moment that you’ll take my story seriously - nor, for that matter, will Seagasso suspend any of its North-Sea commitments - but at least I’ll have the satisfaction of knowing I tried to warn you.
Now I ask you to remember what Borszowski said about great, alien beings lying asleep and imprisoned beneath the bed of the sea; “gods” capable of controlling the actions of lesser creatures, capable of bending the very weather to their wills - and then explain the sight I saw before I found myself floundering in that mad ocean as the old Sea-Maid went down.
It was simply a gusher, Johnny, a gusher - but one such as I’d never seen before in my whole life and hope never to have to see again. For instead of reaching to the heavens in one solid black column - it pulsed upwards, pumping up in short, strong jets at a rate of about one spurt in every five seconds - and it wasn’t oil, Johnny - oh God! - it wasn’t oil! Booze or none I swear I wasn’t drunk; not so drunk as to make me colour-blind, at any rate!
Like I said, old Borszowski was right, he must have been right. There was one of those great god-creatures down there, and our drill had chopped right into the thing!
Whatever it was it had blood pretty much like ours - good and thick and red - and a great heart strong enough to pump that blood up the bore-hole right to the surface!
Think of it, that monstrous heart beating down there in the rocks beneath the sea! How could we have guessed that right from the beginning our instruments had been working at maximum efficiency - that those odd, regular blips recorded on the seismograph had been nothing more than the beating of a great submarine heart?
Might be Howard Fast's The Wound. The theme is that Earth is a living organism and that human activities are penetrating through the skin to vital parts underneath, causing it pain and injury.
It is anthologised in The General Zapped an Angel and in Aldiss' Evil Earths.