Carbonate excess permeability in pressure transient analysis: A catalog of diagnostic signatures from the Brazil Pre-Salt

Abstract

Dynamic appraisal in carbonates with excess permeability is critical to successful reservoir modeling and depletion planning. Accurate recognition and characterization of a dual-porosity system may translate to improved project performance. We present a catalog of diagnostic signatures that elevate pressure transient analysis beyond the traditional V shape, to aid in identifying non-matrix features’ presence, extent, and contribution to reservoir performance. We reviewed 152 well tests from the Brazil Pre-Salt, integrated with multi-scale static and dynamic data (conventional core, borehole image logs, seismic, and drilling losses). A recurring set of eight signatures with characteristic slopes and shapes stood out, which we reconciled with geologic concepts and tested with numerical modeling. These signatures reveal key insights into excess-permeability architecture and non-matrix types, from touching vugs to caves, from natural fractures to fault damage zones. They will assist subsurface teams to optimally frame well test objectives and maximize value of information during early appraisal and field development. They will help enhance reservoir performance prediction, by enabling a comprehensive use of well test data in geologic and reservoir simulation models.