Pore Pressure module
Purpose
The Pore Pressure module enables users to calculate the pore pressure in the shale intervals using the Eaton sonic and resistivity methods. Pressure can be calculated as either instantaneous or accumulated.
Primary Outputs
The following curves are the primary interpretations made in this module.
| Curve Name | Description |
|---|---|
| PORE_PRESSURE_FINAL | Pore pressure via selected method |
| OVERPRESSURE | Pressure above hydrostatic |
| HYDROSTATIC | Hydrostatic pressure |
| OVERBURDEN | Lithostatic pressure |
Discussion
The user has options for entering the hydrostatic and lithostatic pressure gradients. Lithostatic will preferably be calculated from the density curve if available. These two curves are useful calibration points and are displayed in the pressure track.
The Vclay Cutoff parameter allows the user to set what is considered “clay” for the purposes of the Eaton methods, which only calculate pore pressure in clay-rich intervals. Everything greater than or equal to the value will be used for calculations and will be highlighted in red on the Vclay track.
The Final Pore Pressure Method allows the user to select which results will be used when calculating overpressure and when moving into the Geomechanics and 1D Geomechanical Earth Model modules.
The parameters for the Eaton and Modified Eat methods are available for each method.
The results are all shown on the second track from the right along with the hydrostatic and lithostatic pressures. The Overpressure curve is a composite of the hydrostatic pressure gradient and the overpressure from the final pore pressure method, if present.
Users should keep in mind that:
- When evaluating pore pressure it is important to ensure that you are able to match the hydrostatic pressure in zones that are not suspected to be overpressured. This is a valuable anchor point.
- The Eaton methods should only be applied to shales. The Eaton resistivity method almost always underestimates pressures in organic shales because of the excess resistivity due to hydrocarbon presence.
- Pore pressure can either be calculated as accumulated or as instantaneous - there are use cases for each.
Here is an additional tutorial video.
Related Insights
Quick Start Module
Purpose The Quick Start module is designed to help users quickly set dozens of common parameters by selecting a handful of basic options from dropdown menus. Parameters There are three parameters that are set on a zone-by-zone basis and two parameters that are set on a full-well basis. These are as follows. Discussion The parameters are linked to what are called named_defaults in the software. These are collections of defaults that can be set through assigning a single parameter.
Making Log Calculations in a Flow
This articles provides an overview of how to use a Flow to before basic log calculations. To do this, the following Flow tools are used: LogInput >> Bring the log data into the Flow LogMath >> Perform some calculation LogOutput >> Writes the log data to a new log database. There can be as many LogMath tools added to a flow as one would like, and they can be added to existing Flows ushc as a Log Clean-up Flow. The LogMath tool is extremely flexible.
Sample data to get started
Need some sample data to get started? The files below are from data made public by the Wyoming Oil and Gas Commission. These will allow you to get started with petrophysics, mapping, and decline curve analysis. Well header data Formation tops data Deviation survey data Well log data (las files) Production data (csv) or (excel) Wyoming counties shapefile and projection Wyoming townships shapefile and projection Haven’t found the help guide that you are looking for?