Capillary Pressure Tutorial: Part 2 - The Path Out of the Jungle
- E. C. Thomas (Bayou Petrophysics)
- Document ID
- Society of Petrophysicists and Well-Log Analysts
- Publication Date
- October 2018
- Document Type
- Journal Paper
- 557 - 563
- 2018. Society of Petrophysicists & Well Log Analysts
- 5 in the last 30 days
- 323 since 2007
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At this juncture you are feeling pretty good; you know what capillary pressure is and how to determine it in the laboratory. But I pose this question to you: Now that you know what capillary pressure is, how do you expect to use this information to improve your knowledge about rocks and improve your computation of reservoir saturations? “Haven’t a clue,” you say. Well, this tutorial will help you learn the “magic” of using a capillary pressure model to check your well-log interpretation and to finally understand relative permeability measurements. To do all of this, we will draw upon our previous discussion on cohesion, adhesion and wettability and add on some more fundamental physical chemical phenomena, specifically (1) the subsurface force of buoyancy, and (2) imbibition and drainage of fluids in subsurface reservoirs. All aboard the Capillary Pressure Express now leaving the jungle! Fasten your seat belts and hang on! We may encounter turbulence as we pass through the jungle/understanding interface!
The first stage in the discussion of buoyancy must begin with a rough understanding of how sandstone reservoirs originate. We will use the example of the USA Gulf of Mexico, but the concepts are true for any other sedimentary basin in the world. Somewhere in a mountain range several tens of thousands of feet above sea level, rock formations exposed to the elements, experience weathering, etc., which result in small pieces of the rocks to spall of the rock surface (it may be as small as individual grains) and fall to the ground where they can be exposed to rain water of various quantities sufficient to move the rock fragments and grains into streams, then rivers, then into the Mississippi River and finally dumped into the Gulf of Mexico where they settle to the water bottom and accumulate into laminae, beds, and formations.
|File Size||3 MB||Number of Pages||7|