The Tellian Atlas Subthrust Play--New Life for an Old Province

BARR, D., J. A. SCOTT, P. R. SHINER, and D. N. SMITH, B P Exploration, London, England, Z. DJERROUMI, L. BENAKILA, and B. MAACHE, Sonatrach Exploration, Algiers, Algeria

The Tellian Atlas is a south-directed, thin-skinned thrust belt in northern Algeria.

One of Algeria's first producing oil fields, Oued Gueterini, was discovered in the Tellian Atlas in 1948. No follow-up discoveries have been made, and Oued Gueterini has produced only 5 million bbl of oil, although numerous hydrocarbon seeps have been recorded in the frontal thrust belt, north of the Miocene foredeep.

The Tellian Atlas formed in the late to middle Miocene in response to collision between the Kabylis microcontinent and North Africa. Its complex structural history includes out-of-sequence thrusting and decapitation of early halokinetic and thick-skinned inversion structures.

The Tellian Atlas comprises Mesozoic sediments of the Tethyan passive margin, marginal-marine Eocene and Oligocene-Miocene flysch, and molasse. Severe imbrication limits the preservation potential of thrust-sheet prospects; recent attention has been focussed on subthrust plays.

In 1989-1990, BP and Sonatrach carried out a joint study to evaluate the potential for new plays within this old oil province. Initial results were encouraging. Fieldwork and examination of log and seismic data confirmed the presence of two source intervals (Cenomanian-Turonian and Eocene) and of reservoirs with good to excellent potential.

Effective exploration of this technically difficult subthrust play will require the use of such techniques as rugged-terrain seismic acquisition, raypath modeling, indirect prediction of subthrust structures from surface geology, sedimentary facies analysis, and thermal history/source-rock modelling.

AAPG Search and Discovery Article #91007© 1991 AAPG International Conference, London, England, September 29-October 2, 1991 (2009)