Seismically Integrated Geologic Modeling: Guntong Field
Authors: Ismail Mohd N. , Calvert Craig S. , Helwick Sterling J. 
Published: December 2007

Exxon Production Research Company, Esso Production Malaysia Inc., and Petronas Research & Scientific Services participated in a joint research project on seismically integrated reservoir modeling involving the Guntong Field, Malay Basin. The goal of this effort was to develop and test a process for interpreting reservoir properties from 3-D seismic data and for integrating these data into the building of 3-D geologic models that would be suitable for use in flow simulation studies.

The project produced a 3-D geologic model for three reservoir intervals (IR010, IR023, IR025) and three predominantly non-reservoir intervals. Each reservoir interval was subdivided into facies that were determined by integrating core, well log, and seismic interpretations. The reservoir properties of each facies were modeled independently, producing a geologic model that preserved the unique distribution of reservoir properties that characterized each facies.

Predictions of porosity and lithology used in building the geologic model were made using seismic attributes calculated from acoustic impedance data. The strong DHI in the reservoir intervals assisted in interpreting sandy versus shaly lithofacies. The geologic model was built following a sequential process that produced a lithology model, a porosity model, and a permeability model. Each model was generated using geostatistical simulation techniques that integrated seismically interpreted facies reservoir properties, and reservoir property continuity into the process of cell estimation.

Two sets of geologic models were built to assess the contribution of seismically derived reservoir properties to the accuracy of the geologic models. The set of seismically integrated models was built using all of the information that could be interpreted from the seismic data. The set of seismically guided models was built excluding only the seismically derived reservoir properties. Flow simulation results show a significant improvement in history match using the models that integrated all the seismic information.

Introduction

The availability of three-dimensional geologic models of fields that are in the early stage of development has become increasingly important as the oil industry attempts to estimate reserves and develop depletion strategies for major fields that must be developed in a fast-track mode. Fields in early development have few wells with which to guide the interpolation of lithology, porosity, and permeability. Geologic models that are based on limited well control are potentially very inaccurate descriptions of the reservoir. Inaccuracies in geologic models can carry through to flow simulation studies and can impact estimates of reserves and reservoir performance.

The accuracy of geologic models can be improved by integrating information interpreted from a 3-D seismic survey, which is often available early in the development planning process. Seismically interpreted stratigraphy, facies and reservoir properties are a valuable source of information for predicting reservoir properties between wells and away from well control. Geologic models of sand percent, porosity, and permeability can be improved by integrating seismic-based data with well data, provided that a consistent process is applied from data interpretation to geologic modeling.

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