BHI Differentiation of types of fluvial system: Triassic, Ourhoud Field
Study aims: to assess the dominant fluvial facies and their distribution within a refined reservoir zonation in order to constrain reservoir architecture and modelling scenarios.
Database: over 30 UBI datasets calibrated with 22 fully cored wells with re-orientated photographs.
Approach: definition of a reproducible image facies and dip classification scheme with calibration of core observations to guide sedimentological interpretations.
Integrated results: differentiation of high vs low-sinuosity channels has been achieved by identification of the dominant macroforms (ie. laterally accreted vs downstream accreted bedset stacking patterns), together with the main component bedforms (ie. tabular vs trough cross-bedding). Such differentiation is important to better understand facies scale internal heterogeneity and potential permeability anisotropy.
Low-sinuosity channels are dominated by tabular cross-beds with the dip azimuths of bounding surfaces between successive sets mainly parallel to subparallel to the component cross-beds (<60°; downstream accretion).
High-sinuosity channels tend to be dominated by trough cross-beds with bounding surface dip azimuths being >60° to that of component cross-beds (lateral accretion, ie. point bars).
The distribution of high and low-sinuosity systems within an event stratigraphic correlation has allowed effective mapping of the fluvial styles across the field, and together with pressure data results, resulted in an improved understanding of the depositional architecture and connectivity.