Application of an Integrated Approach to Preserve Geologic and Seismic Consistency in a History Matching Workflow of a North Sea Chalk Reservoir

Abstract

Abstract Reservoir surveillance using 4D seismic has become a valuable resource for managing decisions under uncertainty. This paper highlights an integrated workflow to preserve geological consistency while calibrating a reservoir model using 4D seismic and production data. We demonstrate a successful application of this approach on our North Sea chalk reservoir undergoing waterflood, where a number of repeat seismic surveys have been acquired over time and leveraged as a quantitative source of information for describing the spatial distribution of reservoir properties and compaction. This seismic monitoring data has resulted in the ability to better manage the waterflood by providing fluid movement insights and subsequent improvement of infill well placement. To capture geologic variability and ensure model predictability, geostatistical parameterization techniques using multiple-point statistics are used to represent the uncertainty in the reservoir model. Additionally, the workflow employs a rock physics model to generate a synthetic 4D seismic response from flow simulation. Inconsistencies between the predicted and observed 4D differences are used to classify the reservoir model shortcomings. The uncertain geological parameters are updated in an optimization loop through the minimization of a misfit function comprised of both production and 4D seismic misfit formulations. The closed-loop workflow is managed by an in-house computer-assisted history matching tool using a stochastic optimization algorithm. The integrated approach yields improved reservoir management by encouraging multi-disciplinary collaboration between geological, geomechanical, geophysical and reservoir engineering disciplines. Introduction The use of 4D seismic has proven to be a valuable resource for managing decisions under uncertainty. The task of reservoir history matching is generally an ill-posed problem because there exist as a number of potential parameter combinations that generate similar simulated reservoir pressure and production responses. The fundamental reason this occurs is history matching spatially distributes uncertain geological or dynamic parameters (e.g. porosity, permeability, etc.) using localized well information from production data. The geological parameters in between the wells remain largely uncertain or unknown. To reduce inter-well uncertainty, the spatially more dense 4D seismic data can be used to mitigate the non-uniqueness by reducing the number of acceptable models. A fully integrated workflow has been developed to ensure the predictability in our model forecasts by preserving the geologic and seismic consistency. This workflow dynamically couples all elements of the seismic to simulation workflow by using a computer-assisted history matching procedure.