Reservoir compartmentalization phenomenon for lower Safa Reservoir, Obaiyed Gas Field, North Western Desert, Egypt

Abstract

Obaiyed gas/condensate field lies in the west flank of one of the biggest sedimentary basins in northern part of Western Desert at southern coast of the Mediterranean Sea and produces from Khatatba Formation which overlays the Paleozoic high with unconformity surface at a depth of about 4000 m. Although this field is one of the most vital gas fields in Egypt, it is considered as tight gas producer which suggests the presence of highly compacted reservoirs that occasioned by the severe cementation of digenetic cements. It has a big complexity in lithology and structure, which may divide the reservoirs into many compartments. Accordingly, most of the production wells have been suspended after drilling while all the given data from the wells indicates that this area is characterized by high reserve and remaining the reason unspecified. This study aims to overcome the challenges of detecting the high reserved compartments and gives us better understanding of the subsurface production scenarios. Depending on the resulted structured 3D model, 3D facies model, pressure data analysis, fluid contacts, qualitative and quantitative faults seal analysis around the area, and by comparing these results with the geology of the area obtained that the whole area is compartmentalized by fault due to increasing the percent of Illite and Kaolinite shale on the fault planes as a result of inverting most faults in Late Cretaceous to early Tertiary compression event.