A new methodology to describe fractured reservoirs by construction of geological models calibrated to well test data is evaluated by case application. The aim of the approach is to construct a three-dimensional (3D) fracture/matrix model that represents the main components of the reservoir architecture. The model allows a close approximation of complex geological features. The geological model is calibrated against well tests to determine the geometrical and single phase flow properties required to reproduce the well test. This process may allow discrimination between different equally plausible geological scenarios and the output of the approach has implications for input to reservoir simulators.
Input to the model includes the seismic-scale reservoir structures, the geological layering and observed intersections with flowing fractures in wells. A structural model is built within this framework in accordance with the geologist’s understanding of the fracture system and geomechanical principles. The structural model is comprised of surfaces, which may represent individual fractures or, alternatively, may represent more complex geological features including fractured layers or fault zones. The matrix is represented either implicitly or explicitly.
A case application is described where three well tests in the same reservoir volume are modelled. All three well tests were matched within the same internally consistent geological model, which previously had not been achieved using standard analytical well test analysis tools. This may illustrate the advantage of utilizing a more realistic geological model. Having established a series of models consistent with both the geological and flow data it becomes possible to identify the key components of the model that must be represented in a reservoir simulation model.