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Sensitivity Analysis

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In general sensitivity analysis, the most influencing parameters are identified through building a statistical linear model, partial t-test, and Analysis of Variance (ANOVA). Sensitivity analysis was conducted through Design of experiments (DoE) in order to determine the most influencing geological parameters on the Gas Assisted Gravity Drainage process performance. DoE combines multi-level of each parameter to create many computer experiments evaluated by the compositional reservoir simulation to obtain the flow response factor. In this study, the parameters adopted for sensitivity analysis are horizontal permeability, anisotropy ratio $K_{v}/K_{h}$, and porosity, all given for the entire reservoir. First, more than 80 computer …show more content…

Moreover, this fact can be also observed in Figure ~\ref{fig:sa1lm} that decorates the component-residual plots for each parameter. If a variable has a horizontal straight line of residual, it has no effect on the response and should be removed from the linear model, specifically the porosity variable. Figure ~\ref{fig:sa1_lm} shows the basic diagnostic plots for the full linear model. The residuals vs. fitted plot is used to determine if the linear relationship between the predictors (parameters) and outcome factors are captured by the model. An accurate model will have a residuals vs. fitted plot with a horizontal line with residuals above and below it without forming a pattern or grouping, as seen in the top left plot. Moreover, the normal Q-Q plot, shown in the top right plot, is used to determine if the residuals are normally distributed. A good normal distribution will have a normal Q-Q plot which follows a straight line, as do our results. Furthermore, the Scale-Location plot shows if the residuals are spread equally along all ranges of the predictors. Ideally, the residuals should be randomly spread across all fitted values and not tend to one area, as ours do in the bottom left plot. Likewise, the Residuals vs Leverage plot determines how big of an impact outliers points have on the regression curve. Additionally, outliers away from the Cook’s distance will have a large

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