Seismic Facies Analysis for Fracture Detection : a Powerful Technique

摘要

Fractured reservoir analysis requires an accurate delineation offracture corridors, as well as an estimate of the fracture density.Fracture corridors are often closely associated with faults, large andsmall. 3D seismic data is of great help for minor “sub-seismic” faultdetection and characterization, small faults being often expressed asvery subtle zones of deformation (discontinuities), with no obviousoffset of seismic reflections.A large number of seismic attributes are known to highlightdiscontinuities. They can be horizon-based, such as curvature, dip,edge, azimuth or based on the 3D seismic trace variability in a givenneighborhood such as “coherence-type” attributes or computed afterFourier or Hilbert transform as instantaneous phase or frequency.This paper proposes, in a large Upper Cretaceous carbonate reservoironshore UAE, to use jointly a set of selected “fracture relevant”attributes in a multi-variable statistical process called Seismic FaciesAnalysis (SFA). The resulting seismic facies map delineates areasspatially oriented towards two directions that are consistent with thegeneral structural knowledge of the field. Analyzing seismic attributedistributions within each seismic facies gives a preliminaryinterpretation of these seismic facies in terms of fracture density. Thevalidation of this interpretation with well data (BHI, core anddynamic data) delivers an accurate map of fracture occurrence. Thismap is then used to interpret structural lineaments and constrainstochastic realizations of the fracture model.