Seismically Integrated Geologic Modeling: Guntong Field, Malay Basin
Authors: Calvert Craig S. , Helwick Sterling J. , Hill Rob E. , Hubbard R. Scott , Khare Vijay , Wahrmund Leslie A. , Wang Gann-Shyong 
Published: December 2007

Abstract
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. 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 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. 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 lithology, 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.
Therefore, a process for building geologic models incorporating 3-D seismic interpretations was developed and applied to Guntong Field to aid in the development of the western side of the field and to improve the accuracy of the current geologic model of the central and eastern parts of the field.

Field Overview
Guntong Field is located in the Malay Basin. The reservoir is segmented into three fault blocks by a N-S trending fault system (Fig. 1). Although more than 100 exploration and development wells penetrate the east and central fault blocks, no development wells had been drilled in the west fault block when this study was initiated. This study focused on three reservoir intervals (IR010, IR023, IR025) which occur at the top of the Miocene I Group. These reservoir intervals account for nearly 90 percent of the reserves in the field.
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