--> ABSTRACT: Tracing Oil-Leg Potential in Gas Discoveries: Application to Gas Fields in Papua New Guinea, by F. W. Krieger and P. J. Eadington; #91021 (2010)

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Tracing Oil-Leg Potential in Gas Discoveries: Application to Gas Fields in Papua New Guinea

KRIEGER, FRANK W. and PETER J. EADINGTON

Mapping of palaeo formation water salinity and oil charge history in Papua New Guinea has resulted in the development of a model that can be used to constrain the risk associated with drilling for gas displaced oil-legs.

Fluid inclusion evidence indicates that the Juha gas discovery originally contained a gross oil column of at least 160 feet. A GWC has not been established for the Juha field which contains gas at dew point suggesting the potential for an associated down-dip oil leg.

ROI{TM} measurements suggest oil charge in the Papuan Basin trapped irreducible water with salinities of 50,000 to 80,000 ppm. Irreducible water is likely to be shielded by present day high oil saturation from flow of current formation water with salinities of 6,000 to 15,000 ppm. ROI{TM} measurements at Juha indicate that irreducible water salinity was also 50,000 to 80,000 ppm suggesting oil charge to the Juha structure,occurred at a similar time to other Papuan Basin oil discoveries.

The presence of low salinity fluids in fluid inclusions from water zone samples in three PNG oil discoveries is consistent with trapping of current meteoric formation waters. However, the absence of low salinity fluids, representative of current formation waters, in fluid inclusions from oil zone samples suggests oil charge in this region preceded the introduction of present day meteoric waters.

In contrast the presence of low salinity as well as high salinity fluids in fluid inclusions from the Juha palaeo-oil zone suggests that meteoric water gained access to the reservoir and that loss of oil occurred prior to gas charge. This information indicates that there is limited potential for an oil leg displaced by the current Juha gas charge and has implications for constraining the risk associated with this play type in the Papuan Basin.

AAPG Search and Discovery Article #91021©1997 AAPG Annual Convention, Dallas, Texas.