Controls from Column Height Distribution — A Multi-Seed Stochastic Approach to 3d Fault Seal Analysis
James Pickens, Maartje Koning, Hilbrand de Vries, and Neil Smyth
Shell International E&P, Rijswijk, Netherlands
Fault seal analysis has traditionally employed workflows that include juxtaposition analysis and/or calculation of column height associated with the capillary entry pressure of fault zone material. The emphasis on the relative importance of shale gouge ratio (SGR), vs juxtaposition controls on column height, as well as the need for stochastic analysis of each, varies from one camp to the next. Regardless of which process is applied, quite often any sensitivity analysis of fault seal parameters is disconnected from the original input (interpretation and supporting data) and the uncertainty of the results is difficult to quantify. Commonly, this lack of a feedback to the interpreter, and the inability to establish relevant uncertainty, reduces credibility of the result.
We offer a multi-seed stochastic fault seal analysis workflow that addresses variations in container geometry, fault throw and stratigraphy. Through the use of geocellular models, the user can perform three-dimensional fault seal analysis while stochastically varying one or more of these customizable parameters. By doing so, sensitivity of results to variations in input can be established and validity of column height distributions can be better assessed (i.e. what makes it a big column versus a small column). Further, contact dependencies between adjacent fault blocks can be evaluated by tracking juxtaposition leak points and associated SGR, through stochastic trials. In addition, for each trial, mechanical seal capacity and structural spill is reconciled with fault leak to establish column heights on a per segment, per reservoir, per trial basis. Ultimately, the results are convolved to establish column height distribution and associated volumetrics.
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