Controls on reservoir heterogeneity in permian shallowwater platform carbonate reservoirs U S A implications for secondary recovery

Abstract

تنتج منصات المياه الضحلة، والتي نقوم على المكامن الكربونية من العصر البرمي، أكثر من نصف الزيت الخام المستخرج من الحوض البرمي وتعتبر إحدى أكبر مناطق إنتاج الزيت الخام في الولايات المتحدة الأمريكية ورغم انقضاء أكثر من سبعين عاما على إنتاجها والتي تم خلالها عمليات تطوير بدائية ووسطية ومتقدمة ؛ فإن هذه المكامن مازالت تحتوي ما يقارب ثلثي زيتها الأصلي هذا ويعزي انخفاض كفاءة إنتاجها إلى عدم الإلمام التام بالتركيب الطبيعي وإلى تغاير الصفات البتروفيزيائية التي تميز هذه المكامن والتي تتحكم في انسياب الموائع التحسطية (تحت السطحية)

Shallowwater platform carbonate reservoirs of Permian age have accounted for more than half of the oil production in the Permian Basin one of the largest oil producing regions in the United States Despite more than 70 years of production activities including advanced primary and secondary development however these reservoirs still contain as much as twothirds of the original oil in place This low recovery efficiency is linked to an incomplete understanding of the geological and petrophysical heterogeneities that characterize these reservoirs and control fluid flow in the subsurface Integrated outcrop and subsurface studies of Permian reservoir successions in the Permian Basin illustrate that heterogeneity is significantly the product of the combined effects of original depositional patterns and subsequent diagenesis Importantly the relative contribution of each of these to the development of reservoir porosity and permeability varies systematically across the depositional platform and through the stratigraphic succession in concert with topography depositional environment a relative changes in sea level Accurate modeling and simulation of such reservoirs demands detailed characterization of subtle but significant changes in depositional and diagenetic facies which can best be accomplished by applying integrated models of geological and petrophysical architecture best obtained through a synthesis of outcrop and subsurface studies The paper describes the styles and causes of heterogeneity in Permian reservoirs of the Permian Basin and illustrates the importance of such investigations in designing optimum strategies for recovery of remaining oil resources Experience from the Permian Basin suggests that maximum recovery of the original oil resource depends upon application of these types of studies early in the reservoir exploitation history and preferably before secondary recovery operations have begun