Integrated 3-D Geological Modeling of the C1 Sands Reservoir, Maui Field, Offshore New Zealand

Abstract

Integration of core descriptions with paleontological data and a core-derived, paleomagnetic reversal stratigraphy have been used to provide a new conceptual depositional model for the Eocene C1 Sands reservoir of the giant Maui gas-condensate field. The lowest interval of the C1 Sands was deposited in coastal and lagoonal environments. A subsequent fall in relative sea level gave rise to progradation of channel-fill sands that form a multilateral, multistory sand body. Dipmeter data suggest that the lowermost story of these coalesced channel fills was tidally influenced. The bulk of the overlying C1 Sands was deposited as highstand, regressive shoreline sands that are partitioned by thin, tight transgressive deposits. A lowstand valley was incised into these sediments in the eastern and southern parts of the field. The fill of this valley is interpreted to be of a different age from laterally adjacent shoreline sediments on the basis of the paleomagnetic reversal stratigraphy. This model has been extended from the cored wells by careful calibration and correlation of wireline log response from all wells. Both the landward and seaward pinch-out of the shoreline sands have been delineated by interpretation of amplitude displays derived from the 3-D (three-dimensional) seismic data. The lateral extent of the lowstand valley fill is also defined by the 3-D seismic data. The well and seismic data have been combined, within a sequence stratigraphic framework, to construct a 3-D geological model of the field that is consistent with the dynamic performance of the reservoir and has been used to construct a 3-D reservoir simulation model. In the numerical geological model, sediment body thicknesses are defined on the basis of well data, and their lateral extents are constrained by the 3-D seismic data. The 3-D seismic data volume contains both chronostratigraphic and lithostratigraphic information that has been used to construct the reservoir model.