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ABSTRACT: An Integrated Approach to Characterize Early Miocene Tidal Sandstone Reservoir in the Kulin field, Central Sumatra, Indonesia

Sulistyo, A.1, K. Kelsch2, V. Noguera3, M. Djamaludin3, A. Linawati3, J. P. Logan4, T. L . Heidrick3, A. Desman3, J. Peifer3, K.D. Kimber3, R. Sigit3, A. Harding5 (1) P.T. Caltex Pacific Indonesia, Duri, Indonesia (2) P.T Caltex Pacific Indonesia, Indonesia (3) P.T Caltex Pacific Indonesia (4) P.T Caltex Pacific Indonesia, Rumbai (5) Chevron Petroleum Technology Company

A multidisciplinary team within P. T. Caltex Pacific Indonesia pooled geophysical, geological, petrophysical and engineering expertise to characterize the Kulin field, Central Sumatra Basin for enhanced oil recovery. The field contains 500 million barrels of original oil in place; however, oil recovery is low due to high degree of tectonostratigraphic heterogeneity, compartmentalization, facies variations and high oil viscosity. A field-wide 3D faulted geocellular model was built to assess risks and uncertainties in implementing a cost effective EOR workplan.

The Kulin 3D faulted geocellular model was constrained by integrating structural geology, sequence stratigraphy, sedimentology and petrophysics. The interrogation of high quality 3D seismic data with fault architecture, core, formation evaluation, facies and biostratigraphy allowed the grouping of multi-stacked pay reservoirs into seven field-wide chronostratigraphic units bounded by two regional sequence boundaries and five flooding surfaces. Reservoir and non-reservoir rocks were further subdivided into 9 depositional facies and 6 rock types.

Kulin reservoirs were deposited syntectonically as lowstand progradational tidal channels and shallow marine bars. The intervening seals (non-reservoirs) are mostly marine shales and estuarine bay deposits. The chronostratigraphic surfaces were used to define cell boundaries and cell regions in the geocellular model. These cells were later populated using multi-attribute variograms that include rock type, porosity, permeability and water saturation. Well, core and seismic controlled facies maps guided variogram input including thickness, width, length and directionality of the geobodies. A synthesis of results contained within the 3D faulted geocellular volumes yield key information about reservoir performance and future EOR workplan.

AAPG Search and Discovery Article #90913©2000 AAPG International Conference and Exhibition, Bali, Indonesia