The early mapping of the Arabian Gulf, including Qatar, was part of the early Western interest in the region. One of the earliest geographic expeditions of the area was conducted by the Greek explorer Nearchus during the fourth century BC, which was part of the Alexander the Great campaign that occupied Babylon in present-day Iraq. The next phase of exploration was carried out by the Portuguese traveler Afonso de Albuquerque as part of an effort to establish trading posts in the region. During the nineteenth and twentieth centuries, the region attracted the attention of Europeans, particularly British explorers. In 1820, the British Indian Navy executed a hydrographic survey of the Gulf water and mapped its water and coastlines. These efforts were needed to facilitate the safe navigation of the British ships. Later, the British Royal Air Force (RAF) conducted aerial surveys of the area, generating the first detailed maps and charts of its topography and natural resources. The discovery of oil in Iran, Iraq, and the neighboring Bahrain, and the possible competition from the American oil companies working in Saudi Arabia, led the Anglo-Persian Oil Company (the Iraq Petroleum Company—IPC later) to negotiate and sign a deal with the Amir of Qatar. The first IPC geologic expedition arrived in Qatar on the first of March 1926. A 75-year concession was signed between the two sides on May 17th, 1935. On October 6th, 1938, the first exploration well, Dukhan-1 was drilled, and oil was encountered in the Jurassic Arab Formation. The discovery of the North Gas field was achieved by Shell in 1971, which signaled the start of the gas age of Qatar. Among the prominent geologists who contributed to a better understanding of Qatar’s geology are George Martin Lees, Walter Sugden, Anthony John Standring, and Jacque LeBlanc.