Monte Carlo Analysis
The Monte Carlo Analysis module uses a Monte Carlo simulation to estimate errors in a Petrophysical analysis. The user sets up the analysis work flow and enters the distribution of possible errors in the individual interpretation parameters and input curves. The program randomises the input parameters based on user-selected ranges and then runs the work flow. Several thousand passed are made through the work flow with different starting parameters.
The results are cumulated on a depth by depth level and also by zone using the cutoff and summation module.
Crossplots and histograms can be used for analysing the distribution of the results.
The Summary Result listing gives the zonal results sorted by percentiles. Up to 5 user-defined percentiles can be output in the report.
The report allows the user to quantitatively show the errors involved in the interpretation. Rather than reporting a net pay thickness and average porosity the user can give the P10, P50 and P90 net pay and average porosity. These values can then be used for more accurately estimating the errors in the reserves.
In order to access which parameters control the results of the analysis a Tornado type analysis of the input parameters can quickly be made. This varies each parameter separately and then plots the change in results for the change in an individual result parameter. The results are then ordered to form the tornado plot.
This type of plot can be used to focus the interpreter’s attention on those parts of the analysis which have the most significant influence on the final results and not waste their time on refining those parameters which have little influence.
Plot show the error in Porosity, Water Saturation and Clay volume at a depth by depth bases.
Plot shows a log normal distribution of PhiH
Summary report generated by the Monte Carlo Module
Crossplot shows the Vcl cutoff has a strong effect on the result of the Av Phi Res parameter.
Plot shows that the biggest influence on the average pay porosity in zone one is the Vcl cutoff. Parameters like ‘DTLN’ and ‘Res Clay’ have no influence on the results.