Offshore drilling of large diameter holes in rock formations

摘要

A drilling rig comprises a platform (10) supported above a sea surface (14) by legs which extend to the sea bottom (16). A drill guide (30) of rigid open framework construction extends down from the platform to the sea bottom. The drill guide is only minimally affected by turbulent sea conditions because of its open framework construction. A hardenable substance such as concrete (54) is poured into a flexible bag (50) at the lower end of the drill guide to form a solid structure conforming to the uneven sea bottom and having a substantially flat upper surface. Drilling takes place through the hardenable substance and into the underlying sea bottom.