Production and geological implications of the Natih 9C3D seismic survey

Abstract

The Natih Formation in the Natih field is a heterogeneously fractured reservoir being developed by gas/oil gravity drainage. An understanding of the degree and orientation of the fracturing is essential for the optimum development of the reservoir. In order to better understand the fracturing in the reservoir, conventional 3-D (compressional) and limited 9C3D (nine-component, three-dimensional) seismic surveys were made of the Natih field. A revised fault/fracture model was developed from the conventional 3-D survey results in which 'domains' of similar fault/fracture character have been defined. Comparison with well-production data indicates that the domains associated with strike-slip or rotational movements (interpreted as being more fractured than adjacent areas) are zones of significantly higher productivity. The 9C3D seismic survey results also show areas or 'domains' of variable shear-wave time splitting. A comparison of the fault/fracture domains with the shear-wave time-splitting domains shows a close relationship in which areas of highest shear-wave time splitting coincide with those in which fracturing is most intense. The integration of fault/fracture modeling, well-production characteristics and the 9C3D survey results indicate the potential of the latter as a field-development tool in terms of optimizing well locations, well planning and reservoir management decision making.