Pressure and Fluid Contacts · Module P1
Pressure, gradients and the contact chain
The opening module sets out why a fluid contact deserves a course of its own and the physics underneath it. It covers the hydrostatic gradient of a static column, typical gas, oil and water gradients, normal, over and under pressure in a sand, buoyancy, and the depth and pressure references (measured, true vertical and subsea depth; absolute and gauge pressure) that every later step depends on.
- Level
- Intermediate
- Position
- Module 1 of 8
- Video
- About 20 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
- Why the contact can move a volume more than most inputs
- The gradient of a fluid column at rest
- Gas, oil and water gradient ranges
- Measured sand pressure versus shale-trend pore pressure
- Measured depth, true vertical depth and subsea depth
- Absolute and gauge pressure
Learning outcomes
After the module you should be able to:
- Know which depth and which pressure every number is on before fitting anything.
- Convert a fluid density into a pressure gradient and back
- Explain why tests quoted on measured depth cannot be fitted on a deviated well
A short preview
A column of fluid at rest gains pressure at a rate fixed only by its density: 0.433 psi/ft for fresh water, scaled by the specific gravity. Brine of 1.05 gives about 0.455 psi/ft, a light oil of 0.70 about 0.303, and reservoir gas of 0.20 under 0.09. Over a hundred feet those slopes part by tens of psi, so a handful of accurate pressures can tell the fluids apart. Plotted against measured depth on a 35 degree well, the same pressures would show slopes nearly a fifth too low and suggest the wrong fluid.
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.