SCOTT, ALAN J.¹ and WHELLER, DAVID A.^2
1Scott and Associates
²Anadarko Algeria Corporation, London, UK

Abstract: Regional Trends in Triassic Fluvial-Lacustrine Cycles, Berkine Basin, Algeria

Several major recent discoveries in the Algerian Berkine Basin are associated with Triassic fluvial and lacustrine systems. Exploration fairways are broad incised drainage systems associated with the Hercynian Unconformity. Regional base-level changes and climatic cycles influenced the valley-fill stratigraphy. Several two component cycles are recognised. A basal sand-rich fluvial and aeolian component has excellent reservoir characteristics. These intervals are capped by laterally extensive lacustrine shales. Lake-levels fluctuated significantly and associated deltas and debris flows contributed sands to the lakes.

The extensive lacustrine systems form a high-resolution "key-bed" stratigraphic framework. Thus the Triassic argilo-greseux inferieur (TAGI) can be subdivided into more than a dozen thin (>10 m) time - equivalent stratigraphic regional units. Within the major drainage system these units may be mapped for more than 200 m the depositional dip. Significant differences in depositional style along the trend are recognizable. The high-resolution stratigraphy has also been incorporated into reservoir characterization studies of the fields. Several thousand meters of core from more than 100 wells have been used to develop the deterministic model for input into stochastic reservoir models.

The TAGI depositional model has also been compared to modern systems from similar settings, and to surface exposures of ancient analogues. Climatic cycles play an important role in both the modern examples, and we believe the Triassic fluvial-lacustrine cycles.

AAPG Search and Discovery Article #90928©1999 AAPG Annual Convention, San Antonio, Texas