With many oil and gas professionals working in unconventional reservoirs, we may forget or become rusty on the physics of multiphase fluids in reservoirs with variable distributions of permeability. This is because their impact on reserves may be more pronounced in conventional reservoirs. The effects of capillarity in a multilayered reservoir with flow in the aquifer beneath, have characteristic signatures on pressure–elevation plots. This seminar reviews some of the basic physics and how the various aspects would theoretically manifest on capillary pressure curves and pressure-elevation plots if we had data in the perfect locations. We then look at field examples with a case study of the Griffin and Scindian/Chinook fields of the Carnarvon Basin North West Shelf of Australia where such signatures can be observed. The Griffin and Scindian/Chinook fields have a highly permeable lower part to the reservoir, a less permeable upper part and a low permeability top seal. In the Griffin Field there is a systematic tilt of the free-water level in the direction of groundwater flow. Where the oil–water contact occurs in the less permeable part of the reservoir, it lies above the free-water level due to capillarity. In addition to these observable hydrodynamic and capillary effects on hydrocarbon distribution, the multi-well pressure analysis shows that the gas–oil contacts in the Scindian/Chinook fields occur at different elevations. The “take-away” from the seminar will be a refreshed understanding of how a combination of capillary forces and hydrodynamic forces can influence the location of multi-phase hydrocarbon accumulations in porous media, and what signatures to look for in pressure-elevation plots. You will know how the key attributes of a capillary pressure curve manifest on a pressure-elevation plot and the resulting key differences between the location of the free water level and the hydrocarbon-water contact.

свернуть