Full-Field Modeling Using Streamline-Based Simulation: 4 Case Studies

Abstract

Abstract Modern streamline-based reservoir simulators are able to account for actual field conditions such as 3D multi-phase flow effects, reservoir heterogeneity, gravity and changing well conditions. A streamline simulator was used to model four field cases with up to 400+ wells and 150,000+ gridblocks. History match run times were about 1 CPU hour per run with the final history matches completed in about 1 month per field. In all field cases, a high percentage of wells were history matched within the first 2–3 runs. History matching fields with a large number of wells is quite different than matching simulation models with only a few wells. Streamline simulation not only enables a rapid turnaround time for studies, but also serves as a different yet valuable tool in resolving each of the studied fields' unique characteristics. The primary reasons for faster history matching of permeability fields using 3D-streamline technology as compared to conventional finite difference techniques are:Streamlines clearly identify which producer-injector pairs strongly communicate (flow visualization).Streamlines allow the use of a very large number of wells thereby substantially reducing the uncertainty associated with outer boundary conditions. Streamline flow paths indicate that idealized drainage patterns do not exist in real fields. It is therefore unrealistic to extract symmetric elements out of a full field.The speed and efficiency of the method allows the solution of fine scale and/or full field models with hundreds of wells.The streamline simulator honors the historical total fluid injection and production volumes exactly as there are no drawdown constraints, initially.Easy identification of regions that require modifications to achieve a history match.Streamlines provide new flow information (i.e., well connectivity, drainage volumes, and well allocation factors) that is not possible to derive from conventional simulation methods. Introduction In the past, streamline-based flow simulation was quite limited in its application to field data. However, Chevron has shown strong leadership in this application.1 Hybrid streamtube models were used to rapidly history match field data to arrive at both an updated geologic model and a current oil saturation distribution for input to Finite-Difference (FD) simulations. FD simulators were then used in forecast mode. Recent advances in streamline-based flow simulators have overcome many of the limitations of previous streamline & streamtube methods.2–7 Streamline-based simulators are now fully 3D and account for multiphase gravity and fluid mobility effects, as well as compressibility effects. Another key improvement is that changing well conditions, due to rate changes, infill drilling, producer-injector conversions, and well abandonments are now accounted for. With advances in streamline (SL) methods, the technique is rapidly becoming a standard tool to assist in the modeling and forecasting of field cases. As this technology has matured, it is becoming available to a larger group of engineers and is no longer confined to research centres. Published case studies using SL simulators are now appearing from a broad distribution of sources.8–13 Because of the rapid pace of distribution & application of this technology our first intent in this paper is to outline a methodology for where & how streamline-based simulation fits in the reservoir engineering toolbox. Secondly, to provide insight into why we think the method works so well in some cases. Third, to demonstrate the application of the technology to everyday field situations, by mainstream exploitation or reservoir engineers, as opposed to specialized or research applications. The Streamline Simulation Method For a more detailed mathematical description of the streamline method, please refer to the Appendix and subsequent references.