Classification and characterization of barrier-intercalation in sandy braided river reservoirs: Taking Hegli Oilfield of Muglad Basin in Sudan as an example

Abstract

Based on comprehensive analysis of core data, well logs and outcrops, the barrier-intercalations in the sandy braided river of Hegli Oilfield, Muglad Basin, Sudan were classified and analyzed. The barrier-intercalations in single wells were identified using grey theory, which, in combination of the modern braided river deposit measurements, was used to establish the quantitative calculation formulas for different barrier-intercalations in different scale. Three hierarchies of the barrier-intercalations are developed in the sandy braided river reservoirs in the study area, including barriers between the two single layers, intercalations between the two single sandbodies and intercalations in a single braided river bar. The barriers are 700–1 500 m wide and 1 000–2 000 m long, in continuous sheet shape. The intercalations of abandoned channel are 170–350 m wide; the intercalations of chute are 60–100 m wide and 900–1 500 m long; and the intercalations of braided river bars are 100–400 m wide and 300–800 m long. Based on the constraint of barrier- intercalation scale, 3-D geological models which accurately delineate different types of barrier-intercalations were built by facies-control and stochastic modeling. Key words: sandy braided river, barrier-intercalation, channel, braided river bar, hierarchy analysis, characterization method, 3D modeling