Pressure and Fluid Contacts · Module P6
Capillary pressure and saturation height
Above the free water level, water saturation is set by capillary pressure, which grows with height and with the density contrast between the fluids. The module converts height into capillary pressure, takes laboratory core data to reservoir conditions, fits common capillary pressure models, and builds a saturation-height function that ties the free water level from pressures to the contact and transition zone seen on logs.
- Level
- Intermediate
- Position
- Module 6 of 8
- Video
- About 21 minutes, narrated
- Format
- Narrated video lesson with captions and slide reading view; with the certified option, a quiz whose pass unlocks the next module.
What the module covers
- Height above free water level and capillary pressure
- Porous plate, centrifuge and mercury injection data
- Converting laboratory capillary pressure to reservoir conditions
- Brooks-Corey, Thomeer and Leverett J fits
- Entry height and the log contact
- Saturation from height against saturation from resistivity
Learning outcomes
After the module you should be able to:
- Tie the log contact to the pressures and the core through capillary entry height.
- Convert a height above the free water level into capillary pressure
- Explain why saturation from height is an independent check on log saturation
A short preview
At a height H above the free water level, capillary pressure equals the density difference times gravity times H; in oilfield units, 0.433 times the specific gravity difference times the height in feet. With brine at 1.05 and oil at 0.75, sixty feet up gives 0.433 × 0.30 × 60, about 7.8 psi. If the rock needs 3 psi before oil can enter its largest pores, oil first appears about 23 feet above the free water level, and that is where the log places the contact.
Who it is for
Petrophysicists, reservoir engineers and geoscientists who screen formation pressure tests, pick fluid contacts and carry them into volumes for exploration, appraisal and development decisions.
Prerequisites: None required; working familiarity with well logs and volumetrics helps. The hands-on steps use the Pressure Analysis panel in Formation Evaluation.
Take the module in the Learning Hub
Pressure and Fluid Contacts: Specialty course, sold separately: eight modules that turn a formation tester report into fluid contacts you can defend, from screened tests and gradients to capillary entry height and a contact range in the volume. The lesson opens in the Learning Hub once the track is purchased; graded quizzes and the certificate come with the certified option.