Connectivity Between the Ghazal and Mazalij Fields

By

 Matter J. Al-Shammery¹, Muhammad M. Al-Saggaf¹

(1) Saudi Aramco, Dhahran, Saudi Arabia

 The target reservoir of the Ghazal and Mazalij Fields is the Paleozoic Unayzah Formation. The Mazalij reservoir was discovered in 2000, on the down-thrown block of a succession of faults that separate it from the crestal area of the field, where the reservoir was missing. The Ghazal Field was also discovered in 2000, where it encountered a thick Unayzah with excellent sand quality. The two fields were initially thought to be disconnected. Several pieces of evidence (including depositional growth, structural depth, pressure regimes, geochemical analysis, and 3D seismic data acquired later) indicated that the fields may be connected. A delineation well was proposed to test the connectivity between the two fields. In order to select the optimal location for the well, accurate depth maps of the entire Ghazal/Mazalij region were produced. The goal was to generate not only a map of the depth structure of the Unayzah, but also maps of the depth and isopach of all key layers in this region, since this is vital to understanding the growth structure of the reservoir and obtaining a good assessment of the depositional environment in this area. The location of the delineation well was selected to be on the apparent saddle between Ghazal and Mazalij in order to directly settle the issue of the connectivity of the two fields with a high degree of confidence and to afford a much more accurate assessment of the reservoir compartmentalization in this region. The results of this well helped confirm the connectivity between the two fields.