Multi-Scale Karstic Reservoir Characterization: An Innovative Approach to Improve Reservoir Model Predictions and Decision Making

This study consists of an innovative multi-disciplinary approach (combining borehole imagery, core data, 3D seismic and field production) which aims at better characterizing and representing karstic features in a dual porosity/permeability simulation model and improving the associated reservoir model predictions in the context of a carbonated reservoir characterization. The applied methodology can be described as follow: Identification and picking of karstification features on bore-hole imagery (GeologTM software) Deterministic picking of karstic features as geobodies on the 3D seismic (enhanced similarity volume (PaleoscanTM software) Integrated implementation of the karstification features into the geological model using advanced geostastical methods (Multi-Points Simulation, PetrelTM software) Implementation of the resulting enhanced reservoir properties during dynamic simulations and history matching (dual porosity/permeability medium, tNavigatorTM software). After their deposition, carbonate reservoir series are affected by intense karstification during a prolonged period of subaerial exposure. They are consequently marked by widespread erosion; dissolution and collapsing features (e.g., solution cavities, solution-enhanced fractures and brecciated intervals) which were first recognized and picked on the borehole imagery. Typical elongated and dendritical karstic features were then identified through advanced 3D seismic attributes and then deterministically picked as geobodies. This picking was performed using advanced similarity seismic volume, at high resolution, to capture vertical heterogeneities in the karstified interval(s) of the reservoir. Then, Seismic extracted geobodies were implemented as key drivers for reservoir properties into the geological model. Since every brecciated zone on the borehole image could not be captured during the seismic picking (either due to resolution, and/or to low seismic quality zone), an advanced Multi-Points simulation was designed and implemented using the "geobody" property as a "training image" (primary constrain). This method reproduces the characteristics of geobodies, such as trends, orientation, shape, and dimensions. This method filled the resolution gap between seismic image and logs and transferred the multi-scale observations into the geocellular model. The karst-related dynamic properties obtained through this advanced modelling workflow were then refined during history matching and considered as the main driver for variations in well productivity indexes. This tailor-made approach critically impacts redevelopment opportunities that will ultimately safeguard and increase hydrocarbon reserves.