PowerLog - Capillary Pressure

Determine Height Above Free Water

Determining the relative water saturations and height above free water is a critical step in understanding the subsurface and defining an efficient drilling program. With this understanding, reservoir engineers can avoid drilling into free water, determine compartmentalization and identify zones that are in communication.

Using the Capillary Pressure module, geoscientists evaluate well logs and cores from multiple wells and zones to model saturation versus height above free water level (FWL). The resulting analytical expressions relate either connate water saturation to height above FWL (forward modeling) or height above FWL to connate water saturation (reverse modeling). Findings from one well can be applied to other wells in the area, making the process efficient and consistent.

A normal capillary pressure workflow is:

Import core data
Verify/modify lab measurement parameters
Correct data sets for stress, clay, closure and normalization
QC data
Categorize the data sets
Apply a fitting function
QC results
Output the fitted functions

Geoscientists can then determine FWL and saturation versus height profiles in zones and wells.

Interactive Data Loader

To facilitate fast and easy import of data, the Capillary Pressure module features an elegant data loader that quickly assesses input files and identifies columns and sheets of data for import. Data is loaded from ASCII and Excel files and can be in array format. Pressure data is handled in their original units, and saturation is automatically computed from fluid volumes as needed. When more than one saturation value is available for a single fluid type in the data set, the user can set the desired level.

QC and Corrections

Several viewers are available for inspecting and correcting capillary pressure data.

Spreadsheet-like viewer displays and prints data collections
Crossplot viewer presents multiple core measurement values of a single core at a single depth including core saturation versus pressure, well log saturation versus height above FWL, and pore throat radius versus core saturation
Histograms of porosity magnitude

Users can exclude bad measurements, broken core samples and individual data points. Core samples from different rock types can be grouped to associate sequence sets together.

Stress corrections, clay bound water corrections and fluid system difference normalization are all supported.

Fitting functions

Once the data is QCed and corrected, geoscientists apply their own fitting functions or those supplied with Capillary Pressure. Multiple ‘what-if’ regressions are then performed using the different data sets. Models include Lambda, Hyperbola and Exponential J-Functions, Cuddy, Johnson and others. Users can interactively set cutoffs for the regressions. Results include height above free water, pore throat sizes and the permeability to water, oil and other fluids.

Reporting

Results of the analysis are reported in a wide variety of formats and incorporate information such as well, company, location, core data sets used, and core data sets rejected. Reports can also include notation of the model and parameter values used in the analysis.