TX 75083-3836 U.S.A., fax 01-972-952-9435. AbstractFault network modeling of complexly faulted structuresthose containing hundreds or thousands of faults -can be an extremely difficult and time-consuming process. A variety of methods exist to create the appropriate relationships between the faults, due to truncations, crossing, or offsets due to younger episodes of faulting, but each has limitations. Pillar or node-based techniques are often based on the concept that faults only exist where there are interpreted data; extensions of faults to intersections with other faults and/or truncation of erroneously crossing faults is a manual process, requiring the addition of nodes or pillars to the truncating surface. The location of the intersections can be dictated by the orientation of the pillars of the two faults, and so may not reflect the correct structure. An automatically generated binary tree, or hierarchy, can generate a reproducible fault network, where fault relationships can be stored. However, a binary tree cannot correctly handle all types of fault relationships and has particular difficulty in easily representing crossing faults.Our technique uses a new concept of "fused" fault blocks. It begins with an approach somewhat similar to a binary tree, where each fault defines a hanging wall and foot wall side. However, our technique does not require faults that have an implicit relationship (that is, faults which do not intersect) to be explicitly defined in a tree. Fault intersections are determined from the active areas of the faults. Unlike a strict binary tree, fault relationships here can be modified at any time, as interpretation or data changes.Truncations can be stored and re-used, making the fault network repeatable. The accuracy of the fault network, the flexibility of modeling, and the use of this network to create reservoir grids allows an entire asset team to work with a highquality earth model.
TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractUnderstanding the sealing characteristics of faults is critical in assessing the hydrocarbon potential of traps formed by faults. Fault gouge ratio and juxtaposition analysis have often been limited to a single cross section (a two-dimensional approach) or to a single, isolated fault surface (a partial threedimensional approach). We have now developed a full threedimensional solution for calculating fault gouge ratio. This method uses a continually varying clay volume fraction, a network of faults (isolated, dying and/or branching), and displacement along the fault surface (instead of just the dip component). The structural model used as the framework for this calculation is based on geometric reconstruction techniques that construct faults and horizons in threedimensional space, allowing easy and rigorous calculation of juxtaposition and displacement. These last two items are necessary input to the fault gouge ratio calculation.The steps in calculating fault gouge ratio in threedimensional space are as follows: (1) create structural framework, (2) calculate volume of clay (Vcl) as a continually varying property within this structural framework, (3) determine displacement, allowing for oblique slip, and (4) calculate fault gouge ratio for hanging wall and foot wall blocks, and sum to determine the ratio for every point on the fault Rigorous calculation of fault gouge ratio depends on a robust structural model. With the model described herein, a variety of scenarios may be investigated, thus incorporating uncertainty into the calculation. Determining whether a fault will act as a seal, or whether there is potential for development of leaks during the production of the reservoir depends on many variables. Minimizing the uncertainty in this part of the analysis may provide increased confidence in assessing risk.
fax 01-972-952-9435. AbstractThe technical and economic challenges of exploring and producing in deepwater environments require that risk and uncertainty be reduced as much as possible. One of the major contributors to uncertainty -and therefore risk -is creating a sound structural framework.Sophisticated geostatistical techniques are commonly used to create facies and petrophysical models which are used for analyzing uncertainty and making reservoir management decisions, but the underlying structural frameworks often do not correctly portray the true structure. Current methodologies have limitations to the types of fault intersections, the number of faults that realistically can be modeled, and/or the type of grid that can be generated from the reservoir model.The structural framework is often a compromise between the actual structure and what the modeling system allows, particularly in areas with large numbers of Y-intersections, low angle faults, or reverse faults. We have developed a new technique for structural framework building that takes a unique approach to constructing the initial fault model, where fault relationships and intersections are easily defined and controlled.This technique does not have limitations to the types of fault intersections nor to the number of faults which may be included in a reservoir model, and provides the tools to build a reservoir grid using these complex fault intersections. When the structural framework more accurately represents the interpretation, subsequent calculations such as reserve estimates, analysis of structural uncertainty, or well placement can be made with more confidence.The simplicity of building and editing the fault relationships, creating the stratigraphic model, and building the reservoir grid means that an asset team can easily update a model, test different interpretations, and use the model for both geologic and engineering applications.
fax 01-972-952-9435. AbstractRigorous, internally consistent three-dimensional subsurface models are extremely useful in interpretation, mapping, well planning, and simulation pre-processing. The geospatial technique to create these models has been in use for several years, and complicated, highly faulted structures (including overthrusts and other multi-valued surfaces) have been modeled quite successfully. Often, however, the gridding process used to create the horizon surfaces required additional control points, and the shape of the overall structure was not necessarily continued from one fault block to another. A new algorithm has now been developed that uses a threedimensional model of the faulting process itself to restore data to a pre-faulted condition. Displacement on a given fault surface can vary laterally as well as in depth, and faults which terminate within the model volume are of course accommodated. All horizons are used simultaneously in the process of creating the fault displacement model, which eliminates problems with sparse control or narrow fault blocks. The structural surfaces are then calculated in unfaulted space, and the faulting model is used to transform the resulting surfaces back to the proper structural position. Not only is this algorithm significantly faster, but it also mimics the post-depositional faulting process and produces a geologically consistent model. This consistency and integrity mean that greater confidence can be placed in the model, improving volume calculations and allowing placement of wells with greater precision. The reduced cycle time allows a greater range of scenarios to be modeled and evaluated, thus enabling better risk assessment in complexly faulted fields.
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