Introduction
Modern Well Test Analysis has been greatly enhanced by the use of the Derivative Plot (Log-Log Diagnostic Plot). This plot is the most powerful diagnostic tool for the well test analyst. It is as good a snapshot of your reservoir as you are going to get from well test data. Various flow periods can be displayed in a single graph and many are unique in their look.
Wellbore storage shows as a unit slope line plus a hump in the early time on the derivative. The “hump” is characteristic of a damaged reservoir (positive skin). Infinite acting radial flow is always shown as a flat region on the derivative. Fracture flow following storage is a 1⁄4 slope (finite conductivity) or 1⁄2 slope (infinite conductivity) on the derivative plot. Boundary conditions and other reservoir heterogeneities are shown as changes in slope on the late time derivative. Dual porosity behavior, such as a naturally fractured reservoir, gives its own unique shape to the derivative.
The addition of the primary pressure derivative gives the well test analyst the ability to identify between wellbore affects and actual reservoir response.
The derivative plot should always be used to make your initial interpretation of well test drawdown or buildup data. An analytical model can then be matched to the measured data using parameters from the straight line interpretation off the derivative plot. Be very careful not to over analyse your data. Of course real data never looks exactly like the models. However, by using common sense about what your reservoir can look like and applying a basic methodology, well test interpretation can be fairly straight forward.
Locations
- Calgary, AB (403) 262-4000
People
- Divisional Manager- Steve Dawson
- Account Managers-Loyed Vogel, Dave Townsend
- Well Test Specialists- Keith Armstrong, Alex Oykhman
- Reporting- Pam Cruishank, Jennifer Brazil, Cory Strang, Lynn Kovacs