However, owing to the desert terrain, inland exploration was fraught with difficulties. In 1953, D'Arcy Exploration Company, the exploration arm of BP, obtained an offshore concession which was then transferred to a company created to operate the concession: Abu Dhabi Marine Areas (ADMA) was a joint venture between BP and Compagnie Française des Pétroles (later Total). In 1958, using a marine drilling platform, the ADMA Enterprise, oil was struck in the Umm Shaif field at a depth of about 2,669 metres (8,755 ft).