This paper presents error analysis and applications of a new method for estimating permeability from logs. This method is called PermLog and its development is documented by Semmelbeck et at1. We present an example application of PermLog and show how it can be used with pressure transient testing to characterize complex, low to moderate permeability gas reservoirs. We also present the results of a detailed error analysis in which we determine the expected accuracy of the PermLog permeability estimates. We show confidence intervals expected from PermLog based on assumed accuracy of parameters used in the PermLog analysis.
Well tests in complex multilayered reservoirs can be analyzed with more realistic reservoir models when layer permeability estimates are provided by the PermLog analysis. Monte-Carlo error analysis indicates that at least 80% of permeability estimates from PermLog will be within a factor of 3 of the true in-situ gas permeability when the permeability is in the range of 0.01 to 10 md.
The permeability estimates fine-tuned by matching pressure transient behavior will lead to better performance forecasts and optimization of stimulation treatments and well spacing.