Perched Water Observations in Deepwater Miocene Fields Using Well Logs, Core, and Production Data

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About the Course

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Perched water is occasionally encountered above the main gas- or oil-water contact in stratigraphically and/or structurally complex fields. It is a consequence of localized water entrapment associated with relatively small-scale structural or stratigraphic traps during the migration process. Observations of perched water intervals and their associated transition zones in the exploration, appraisal, or production wells can challenge subsurface characterization workflows and often lead to inaccuracies in in-place volumes estimation. Perched water transition zones are commonly misinterpreted as lithological trends, while local perched contacts found at the bases of sands could be interpreted as segment or field-wide contacts. It is, therefore, important to recognize the presence of perched water and adequately characterize its impact on reservoir volumetrics and production volumes.

We present examples of perched water intervals in two Miocene deepwater fields. In the first example, a clear transition zone associated with perched water is observed in a fully cored gas-bearing sand located several hundred feet above field gas- water contact. The presence of movable perched water is confirmed via direct extraction from core samples (see Fig. 1). The associated saturation profile is evaluated using logs and special core analysis measurements. The chemical composition of extracted water samples is compared with the aquifer waters. In the second example, we present a case of perched water in a reservoir located hundreds of feet above regional oil-water contact. Perched water was detected by comparing resistivity- and capillary-pressure-derived saturation profiles and confirmed with water sample analysis and production data.

The field cases provide examples of movable water located high above field water contact and offer useful analogs for perched water detection in deepwater sandstones. Perched water transition zones saturation is shown to follow a normal drainage capillary pressure profile, and its chemistry differs from the aquifer waters. Perched water pools appear to have a limited volumetric footprint and do not result in large quantities of produced water; however, they still need to be accounted for as a potential risk in deepwater projects.


Your Instructor


Alexander Kostin, M.Sc, SPWLA
Alexander Kostin, M.Sc, SPWLA

Alexander Kostin is a Principal Petrophysicist with Woodside Energy in Houston, Texas, currently working on the Calypso project (Trinidad and Tobago). Prior to his current role, he held various technical and management positions within BHP Petroleum, including Gulf of Mexico Exploration Manager, Eagle Ford Development Geoscience Manager, Petrophysics Supervisor, and a Senior Petrophysicist supporting exploration, new ventures and unconventional development teams.

Alexander started his career as a field engineer with SLB. He holds M.Sc. degree in applied physics and mathematics from Moscow Institute of Physics and Technology in Russia.