Exploration History of Messla Oil Field, Sirt Basin, North Central Libya

Abstract

The exploration history in Libya started in the western part of Libya near the border to Algeria by Esso Company one of the Seven Sisters hopefully that the oil accumulation will extend from El Hasi El Masoudi in Algeria. The first well drilled (Wildcat) was Al Atshan well. There were only oil shows in this well. It was plugged and abandoned. Then Esso Oil Company was given a concession in Sirt Basin in the early fifties by the Libyan Ministry of Petroleum. The exploration history in Messla Oil Field started by drilling the wildcat HH1-65. The field was discovered in 1971 and was located in the southeastern part of the Sirt Basin approximately 40 km northwest of the supergiant Sarir Oil Field. Although in an early stage of development, the field is estimated to contain approximately 3.25 billion bbl. of original oil-in-place. The field was a seismically defined stratigraphic accumulation located on the east-dipping flank of a broad Precambrian basement high. The reservoir is in the Lower Cretaceous fluvial Sarir Sandstone, which wedges out westward on the basement and is truncated by a basin-wide unconformity at the base of the capping Upper Cretaceous marine shales (considered to be the source rocks) and by the seal Busat Formation (Anhydrite Cap). The reservoir consists of two sandstone units separated by a continuous shale bed (Red Shale). Porosity values average 17% and the permeability 500 md. The oil column averages approximately 90 ft, and is productive from an average depth of 8,800 ft, Over 200 km2. Early 1978 production is in excess of 100,000 bbl/d of 40° API oil with a cumulative production of 45 million bbl.