Integrated Reservoir Study of Mature Oil Field Resulted in Rejuvenation of an Abandoned Oil Reservoir to Add New Reserves and Production, GoS - Egypt

Abstract

Abstract An integrated reservoir study was initiated to look for new opportunities in East Zeit field. The working team managed to construct the full field static and dynamic models. The main challenge during the history match phase was the high complexity of the structure, range of uncertainties, and the model running time. The team managed to understand unconventional reservoir aspects such as: (1) The reservoir pressure was sharply decreases as production increases. Then, when the reservoir was abandoned as a depletion drive reservoir the pressure started to increase up to initial reservoir pressure without any intervention. (2) The performance of few wells completed in the above mentioned reservoir was similar to the performance of wells in active water drive reservoirs. Comprehensive work in the history match has been done to calibrate the model and explain the different phenomena in the field. The team explained the pressure increase in the depleted reservoir that it was due to the reactivation of faults which became non-sealing. This resulted in communication with another active water drive reservoir and natural miscibility process. The study recommended adding new off take point in the reservoir to confirm the concept. So, a new well was drilled and confirmed the study conclusion and managed to add more reserves and production in the rejuvenated reservoir after 12 years of shut in. Currently, constructing complete field development plan is in progress to maximize the recovery factor. Reservoir monitoring even after abandonment, especially with unconventional reservoir aspects, is very important to discover new opportunities and maximize the recovery. These opportunities should be managed through the integrated reservoir simulation studies to minimize the risk and cover the uncertainties. Introduction The East Zeit field (EZ) is situated in the southern Gulf of Suez (GoS) in about 240 ft of water (Fig.1). The oil accumulation in the field covers an approximately 27 km2 area. The field is composed laterally of two major fault blocks; the main fault block (MFB) and the east fault block (EFB). Moreover, each major fault block is sub-divided into smaller fault blocks which reflect the complexity of the highly faulted structure. Each major fault block is sub-divided vertically into three main reservoirs (Fig.2). The field was started production in 1985 through two platforms; the wells were flowing naturally in the past and currently some wells are producing by artificial lift and other wells are still flowing naturally.