AAPG FOUNDATION PRATT CONFERENCE: PETROLEUM PROVINCES, 21st CENTURY
January 12-15, 2000
San Diego, California

DONALD C. RUSK, International Consulting Geologist, Houston, TX

Abstract: Libya: Petroleum Potential of the Under-Explored Basin Centers -- A 21st Century Challenge

Recoverable reserves in approximately 320 fields in Libya's Sirt, Ghadames, Murzuk and Tripolitania basins, exceed 50 billion barrels oil and 40 trillion cubic feet gas. Approximately 80 percent of these reserves were discovered prior to 1970. Since then, a less active and more conservative exploration effort has persisted. Complex, subtle and, in particular, deep plays were rarely pursued during the seventies and eighties because of a lack of definitive imaging technologies, limited knowledge of the petroleum systems, high costs and risk adversity.

Consequently, undiscovered resources remain extensive in Libya. These resources could be accessed, if geological and geophysical knowledge, innovation and advanced technologies were utilized effectively. 3-D seismic acquisition will be required to some degree for reliable trap definition and stratigraphic control.

Predictably, most of the undiscovered resources will be found in the vast, under-explored deep areas of the producing basins. Six areas are exceptional in this regard: in the Sirt Basin, the south Ajdabiya Trough, the central Maradah Graben and the south Zallah Trough - Tumayan Trough; and, in the west, the central Ghadames Basin, the central Murzuk Basin and the offshore eastern Tripolitania Basin. These highly prospective basin sectors encompass a total area of nearly 150,000 sq km with an average well density, for wells exceeding 12,000 ft, of one well per 5000 sq km. In or near each of the selected areas, the key hydrocarbon factors: reservoir, source, seal and timing, are established; and reliable trap definition can be reasonably assured with prudent use of state-of-the-art tools and technologies.

In the above mentioned deep troughs of the Sirt basin, the main plays primarily involve the rarely penetrated Lower Cretaceous Nubian sandstone. Secondary targets are Upper Cretaceous and Paleocene carbonates. In the Ghadames and Murzuk basin centers, Ordovician, Silurian and Lower Devonian sandstones are the primary objectives. In the eastern extension of the Tripolitania Basin, in addition to the prolific Lower Eocene carbonate reservoirs, the thick Mesozoic section has considerable potential.

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