Many incidents with jack-up rigs are caused by punch-through of one or more of the legs from an upper zone of stronger soil into a lower zone of weaker soil. The resulting leg plunge may trigger platform tilt, causing possible risk of life, environmental damage and damage to rig. This paper presents a hazard map for the Gulf of Suez (GoS) that allows for early screening of sites with punch-through risks and for appropriate design of site investigation strategy. The hazard zoning relies on numerous data sources, notably regional geological and geomorphological, as well as geotechnical, information from 368 borehole locations. The hazard zoning considers punch-through conditions for conventional sand over clay profiles and for soil profiles with different degrees of pre-consolidation or the presence of cemented layers. Remarkably, hazard zoning was found to be largely independent of the precise geometry and loading conditions of common jack-up rigs used in the GoS. The highest probability for punch-through conditions is in deeper water environments (>50m water depth) and in areas where large wadis bring abundant sediment into the GoS.

1. Introduction

The Gulf of Suez (GoS) is considered the most prolific oil province rift basin in Africa and the Middle East, containing more than 80 oil fields, with reserves ranging from 1350 to just under 1 million oil barrels (Alsharhan, 2003). Many offshore exploration projects, including drilling wells, have been carried out in the GoS and future prospects are promising. The majority of the wells are drilled by jack-up rigs (or mobile offshore drilling units (MODU)). Those common to the GoS usually consist of three latticework legs and a triangular shaped hull, which can be moved up and down the legs by means of a rack and pinion system. Large, nearly circular cans are at the base of the legs.

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