Matching Both Production History and 4D-Seismic Attributes
One of the most challenging fields in reservoir engineering encompasses the integration of all available data in models for the characterization of reservoirs and the reduction of uncertainties in oil and gas production. A reservoir model is a grid populated by petrophysical properties such as porosities and permeabilities. During the field life, many data are collected including production data and since the late 1990s 4D seismic data. We present a general matching workflow to build reservoir models constrained to both production data and 4D seismic data. First, a high resolution 3D geological model is simulated, then upscaled. Secondly, the flow simulation is run. On one hand, it yields simulated production answers, which can be compared to the actual production data. On the other hand, it produces saturation and pressure grids, which are downscaled to the level of the fine geological model. Then, a petroelastic model is used to derive impedances, which are filtered before being compared to the actual impedances. The high resolution model is subsequently perturbed and the entire workflow is repeated until production and 4D seismic data are matched. The gradual deformation method is used to govern model perturbations. Thus, only a limited number of parameters is required to vary the whole porosity and permeability fields and the spatial structure is preserved. The matching process involves the computation of gradients, which is a CPU-time consuming step. The efficiency of the whole process is ensured by distributing these computations on several computers. Using a 3D synthetic case, we evidence the interest and efficiency of our workflow. Numerical tests are performed to quantify the influence of the 4D seismic information.
AAPG Search and Discover Article #90063©2007 AAPG Annual Convention, Long Beach, California