Streamlining the WorkFlow from Structure Model to Reservoir Grid

Abstract

Abstract Reservoir grid models and geologic structure models are often two distinct and unrelated entities. Ideally, these two models would be identical; realistically, however, geologic modeling systems often do not produce high quality reservoir grids, and gridding systems fall short of producing good geologic models. The problem is often one of resolution and the approach taken for fault modeling. When the reservoir grid is designed first, the fault framework and geologic layering is often approximated, and the model is not optimally compartmentalized. Antithetic faults are often a problem in this case. Moreover, geologic models created in one application often need to be transferred to another application for reservoir gridding, resulting in loss of resolution. We have developed a new method for creating a 3D reservoir grid from a high-quality geologic structure model. Here, the geologic model is a fault block-oriented, compartmentalized model which has been created using a unique algorithm for producing internally consistent stratigraphic layers. The fault reconstruction process used in this algorithm conserves volume and produces a water-tight, compartmentalized geologic model, which may include normal faults, antithetic faults (also known as "y" or lambda faults), growth faults, reverse or thrust faults, and multi-valued surfaces such as overturned folds or salt domes. When the reservoir grid is based on this type of internally consistent geologic model, the geologic structure defines the reservoir grid, rather than the grid defining the structure. All types of faults are easily transferred from the geologic model to the reservoir model. Individual faults may be selected for the alignment of the reservoir grid in the I, J or IJ direction; the grid may even conform to a multi-valued surface. The process of transferring the geologic model to a reservoir grid is extremely fast – usually requiring just minutes to grid models even with large numbers of faults. The speed, simplicity of transfer (without loss of geologic definition), and quality of the final product allows the asset team to work together to refine the reservoir grid while maintaining detailed geologic input.