Outcrop characterization of an early Miocene slope fan system, Chelif Basin, Algeria

摘要

The study on outcrop characterization is very useful for geologists and oil finders. There is a complex slope fan system of early Miocene in Chelif Basin. We divided the superimposed basin into two main development stages: an expanding rifting stage (early Miocene) and depression-extrusion transition stage. Comparison of the outcrops with typical subsurface data sets (logs, core, and seismic reflection data) provided criteria for a detailed study of the stratigraphic and lithologic features of the slope fan system. Based on these research methods, a sedimentary model was built. The slope fan system was an integrated series comprising two parts, the lower (S1) and the upper (S2), from the sequence stratigraphy study. S1 was progradational but had both rolling transport and gravity transport attributes. Similar to the Bouma sequence, S1 can be divided into four parts, A, B, C and D, from bottom to top. S2 was retrogradational but comprised four internal-progradational cycles. Some layers comprise planar-laminated and climbing-ripple-laminated sandstone with many fossils. The upper part of S2 was a thick marl bed and an obvious flooding surface. Each part had different lithofacies and sedimentary interpretations. Some formations could be good reservoirs based on both self-attributes and outer properties. Considerable evidence suggested that the slope fan have great hydrocarbon potential.