ABSTRACT: Sequence Stratigraphy and Reservoir Prediction for the Toro Formation, Papua New Guinea

PALMER, S. M., BP Developments Australia Limited, Melbourne, Victoria, Australia, RICK CARTER, BP Exploration, Aberdeen, Scotland, United Kingdom, and TIM VARNEY, BP Developments Australia Limited, Melbourne, Victoria, Australia

A predictive model for reservoir sand distribution in the Toro Formation of Papua New Guinea has been developed through an integrated sequence stratigraphic, sedimentological and biostratigraphic study. Owing to a lack of seismic data the approach has been to apply the stratigraphic principles of Galloway and Vail to outcrop and well data.

Reservoirs sands are contained in 6 genetic stratigraphic units. These are defined by bounding maximum flooding surfaces characterized by low sedimentation rates and the development of high gamma ray marine sediments and condensed biozones. With the assistance of biostratigraphy, the maximum flooding surfaces are relatively easily correlatable over the majority of the systems tract. In the proximal areas the maximum flooding surfaces can be absent due to either nondeposition or erosion during a lowstand or the subsequent transgression.

Sequences boundaries have been recognized within most of the genetic stratigraphic units. They are recognized as sharp based inner shelf/shoreface sands which overly mid-outer shelf, bioturbated muds/silts. The juxtaposition of these facies at the sequence boundary indicates a significant sea-level drop.

The primary reservoirs occur in shelf margin systems tracts. The distribution of these reservoirs is controlled by the relationship between eustatic sea-level fall and the topography left from the previous highstand. Further important reservoirs were deposited during

highstands in shoreface and storm facies. Reservoirs also occur in the transgressive systems tract due to shoreface reworking of both the highstand and shelf margin systems tracts.

AAPG Search and Discovery Article #91015©1992 AAPG International Conference, Sydney, N.S.W., Australia, August 2-5, 1992 (2009)