Carbonate reservoirs are often very heterogeneous and their properties are frequently difficult to understand. The presence of faults and intense natural fractures further increases the complexity that becomes very challenging for reservoir management and field development. This is the case of the Shuaiba reservoir in Idd El Shargi North Dome (ISND) Field in offshore Qatar. The field was discovered in 1960 and was first produced in 1964. The oil is produced from multiple reservoirs, primarily carbonate, on a salt induced faulted anticline. After 1995, when Occidental Petroleum assumed the operatorship role under a Production Sharing Agreement with the State of Qatar, an extensive horizontal well drilling and waterflood campaign resulted in a substantial production increase from the primary Arab and Shuaiba reservoirs. This paper will focus on the Shuaiba development results. New technologies have been applied to effectively manage the Shuaiba waterflood and continuously increase the oil recovery factor in this complex reservoir.
The practical aspects of multi-component seismic technology described in this paper can be applied in any complex fractured reservoir for improving efficiency and increasing recovery.
During 2003-2005, Qatar Petroleum and Oxy acquired and processed a large 4C3D seismic survey over Idd El Shargi field (Fig.1). This technology uses multi-component phones and cross-spread acquisition geometry to record both compressional and shear (converted) waves. The survey ensured full azimuth coverage to offsets up to 3000 m, equivalent to an offset/depth ratio of two for the main target zone, achieving a nominal fold of 240 in the natural bin size, or a trace density of more than 2.7 million traces per square kilometer. The data were processed through a flow that carefully preserved the azimuthal anisotropy (Angerer et al, 2006).