ABSTRACT: Carbonate Reservoir Models: Coupling Depositional Sequence and Pore Network Models in Static 3-D Realizations

CREVELLO, PAUL D. , Petrex-Asia Reservoir and Stratigraphy Consultants, Brunei, SE Asia

The future of reservoir technology will be in the area of improving the definition of resources through enhanced imaging of reservoir bodies and/or fluids and incorporation of fully integrated asset studies. Advances in detection and visualization technologies are leading the next generation of models towards realistic 3-D geologic realizations of reservoir systems. Coupled with integrated studies, the next generation models will offer the opportunity to provide our most robust calibration to date of static geology-based 3-D models. However, the models will only be as robust as their calibration. The error often seen in today’s generation of reservoir models, and predicted to linger, is not created by the lack of imaging techniques but from the lack of fully utilizing supporting integrated data.

The objectives of reservoir models are to resolve reservoir bodies and properties (phi, k, sat) to a level that accurately define rock elements and fluid distribution, to place the reservoir body into a robust 3-D geologic-based framework, and to provide a static reservoir model that serves as the framework for upscaling to multiple-scenario dynamic simulations.

Reservoir stratigraphy is one type of approach that provides the technology asset team with a framework to define reservoir architecture, encompassing the spatial distribution of reservoir bodies, aspect ratios, barriers, conduits, and connectivity. A common ingredient of reservoir models is to define reservoir systems in terms of genetically related stratigraphic elements. However, body imaging, resolution, and calibration of rock attributes, in particular rock architecture and pore network, with logs and seismic are and will continue to be the principal hurdles of future reservoir models. Complex carbonate lithologies and pore networks require key subsurface core sets for robust calibration of well-log and imaging attributes, the principal tools used for building models. Rock calibration with cores is essential for coupling stratigraphic and pore network elements into reservoir architecture and for achieving robust model realizations.

The state of carbonate reservoir modeling is rapidly approaching the stage where realistic models of 3-D high-resolution definition of reservoir architecture will become a common task. Outcrop and shallow high-resolution studies provide guides for developing better and more realistic geology-based reservoir models. Often low-resolution imaging of the reservoir body or constraints imposed by upscaling dilute the geologic complexities of the model, but this does not necessarily negatively impact the model; numerous factors dictate the degree of complexity, or geologic reality, required in the model.

In this talk, I will present lessons learned from case studies of reservoir models, where a number of calibrated data sets have been applied on models of reservoir flow units, barriers, and flow simulations. Critical production concerns addressed include fluid types, communication or isolation, fracture potential and vertical encroachment across permeability baffles and barriers, stratal geometries of reservoir conduits and aquifers. Each example has a different reservoir aspect, whether it’s the reservoir body, fluid, or aquifer that affects final field development strategy. Improved imaging and detection of reservoir bodies, combined with robust calibration, will result in robust static model realizations, which will enable subsequent dynamic reservoir simulations to assess the critical uncertainties facing future reservoir development and management.

AAPG Search and Discovery Article #90916@2001-2002 AAPG Distinguished Lectures