oa 3-D VSP’s provide high-resolution seismic images for improved reservoir monitoring and characterization

Enhanced reservoir characterization and monitoring is necessary to optimize and increase production from the huge Middle East oil fields. Currently surface seismic is used to image reservoir structure and aid in the prediction of reservoir property changes away from borehole control points. With borehole seismic or vertical seismic profile (VSP) images, which provide better vertical resolution and higher signal-to-noise ratio, it is possible to observe more detail and build more accurate reservoir models. In an effort to overcome the limitation of surface seismic to characterize reservoir properties, such as porosity and fluid saturations, a new VSP approach was undertaken. Two high-resolution 3-D VSPs were acquired simultaneously with a new surface seismic survey. At<br>two wells an integrated team comprised of specialists in engineering, drilling, geophysical operations, geophysical applications and seismic interpretation planned and executed two 3-D VSP projects together with a new 3- D surface seismic survey. A 126-level multi-component geophone tool, combined with thousands of source points, made this the world’s largest 3-D VSP. The 3-D surface seismic and 3C 3-D VSP were acquired with the same source points to minimize the associated costs and allow for detailed integration between them. The 3-D VSPs can also be used to monitor saturation changes in the reservoir. A 3-D VSP can be repeated more often and at lower cost than a full-field surface 3-D seismic survey. The results of a time-lapse VSP can be used to determine if 4-D or time-lapse effects are detectable and verify when a full-field 3-D surface seismic should be acquired. Based on the success of this 3-D VSP pilot, other 3-D VSP projects are being planned to help overcome production and monitoring challenges.