ABSTRACT: Integrating Sequence Stratigraphic Analysis and Reservoir Petrophysics : a value-added approach to Reservoir Characterization in Central Sumatra

The value of a sequence stratigraphic framework and its applications to characterizing HC reservoirs in a given field must be measured by two critical yardsticks: 1) how well the framework depicts the actual architecture of both reservoir and non-reservoir rocks and 2) how well it contributes to predicting the present distribution of gas, oil and water in the subsurface. We propose that reservoir characterization practices can be greatly improved by the methodical integration of sequence stratigraphic analysis and petrophysical evaluation.

Sedimentary facies models resulting from core studies during sequence analysis can help control reservoir petrophysical models. Fundamental reservoir properties such as: porosity, permeability, bound fluid volumes, residual oil saturation, and fluid contacts are all quite frequently dictated by grain size variability and hence by sedimentary facies. In sandstone reservoir systems initial formation water salinity may change based on the architecture and connectivity of the permeable sands and the distribution of intervening maximum flooding surface shales. These flooding surfaces can assist the formation evaluation geologist in defining zoned petrophysical and fluid properties at the sequence, parasequence set and parasequence (sand pay) levels. Conversely, recognition of fluid contacts from petrophysical evaluations can assist the stratigrapher in identifying sequence boundaries, flooding surfaces, hardgrounds, erosional lags and other important surfaces.

This paper discusses examples from the Central Sumatra Basin which illustrate these relationships. It also proposes a work flow that optimizes the value of reservoir characterization studies by building on the iteration between the sequence stratigraphic and the petrophysical work.

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