YEMEN - Maarib/Jawf Background

Despite the long neglect of Yemen's interior by foreign companies, the geology of that area remained the subject of interest, particularly in the north-east

of Maarib. As a result, the Sanaa government in 1979 sponsored an aero- magnetic survey.

The results of that survey in 1980 caught the attention of Moujib Al Malazi, a Syrian exploration consultant to Ray Hunt's Hunt Oil Co. of Dallas. He studied data showing a narrow but deep graben with a thicker sedimentary basin than originally thought. He shared his assessment with Dr. Ian Maycock, exploration manager of Hunt Oil's London office, and the two concurred that Pre-Cambrian rock formed the basis for the entire area, later known as the Maarib/Jawf Basin (also known as the Sabatayn Basin).

There was a sharp boundary in the north-west with a Jurassic formation, which in Saudi Arabia has yielded prolific oil reservoirs. The theory was that the north-west/south-east trending graben had started to rift in Jurassic times and accumulated a good thickness of sediment.

In December 1980 Maycock took the data and Malazi's assessment to Ray Hunt in Dallas. Within days Hunt sent a team to Yemen for a further scouting of that area and started negotiations with the Sanaa government.

(Now Hunt is producing 140,000 b/d of light/sweet crude oil from that area - down from 169,000 b/d in mid-1996 and almost 200,000 b/d in 1992. Saudi Arabia in 1992/93 included the Maarib/Jawf region among areas it claimed to be part of its territory).

Addressing a London Geological Society conference in 1990, Maycock explained that the government's 1980 survey had indicated the possibility of a 30,000 sq km sedimentary basin and a fill of 3,500 metres. Subsequent successes achieved by Hunt Exploration Co., he said, were a fine example of rich rewards gained by perseverance and an imaginative exploration in frontier areas.

The Maarib/Jawf area was mostly covered in sand but included a diapric salt anticline with some associated bituminous shales. Close to the basin centre, there was also a basement outcrop. Field work along the margins revealed a Mesozoic sequence 750 metres thick, including important Upper Jurassic sands rich in oil.

On evidence of likely source rocks, the prime targets for Hunt were: possible reservoirs, evaporites to provide structuration and seals, amenable government regulations and, most importantly, a potentially large oil basin.

Subsequent studies concluded that the then shared North-South Yemen border zone nearby, called Wadi Al Ain (later to be known as Jannah block), also contained related strata. The Amal and Iyad oilfields in Shabwa of the southern sector, only about 55 km east of Maarib's Alif field, were found to be of a similar Upper Jurassic reservoir. Later it was proven that they all had the same basin, which aroused the interest of many companies.