Abstract

Ras Budran filed is a massive Nubian sandstone reservoir compartmentalized by major faults acting as partial barriers. Vertical communication is impeded by hydraulically sealing shale layers in the development of three main pressure regimes. The pressure is supported by a combined water injection and aquifer drive. Pre-mature water breakthrough has been observed in the middle of oil leg, which in turn limits the corrective action of the isolation of the watered out zones.

A detailed reservoir characterization and engineering study was implemented with the objective of improving the vertical definitions in the reservoir. New reservoir sublayers were developed based upon open and cased hole log data in addition to the incorporation of core data.

The history-matched model was then used to confidently check the production well pattern, placement performance and then used to investigate the viability of infill wells to improve drainage pattern and sweep efficiency.

This paper discusses the different phases of the field development and how the reservoir management was optimized with time in order to access the remaining reserves of the field.

Objective

The objective of this paper is to highlight how the reservoir management strategy was adopted during the field lifetime in order to optimize the actual field performance now and maximize field recovery.

The main objective of the reservoir management strategy was to provide company management with technical guide-lines/forecasts in order to maximize ultimate recovery and production from a reservoir under the prevailing economic and regulatory constraints. In order to provide above technical guidelines an understanding of recovery mechanism and historical, a field/well performance has to be established. On this basis, reservoir performance is analyzed and reservoir management strategy formulated with the application of analytical methods and numerical simulation.

Introduction

Ras Budran field (R/B) is located at the eastern coast of the Gulf of Suez area (Fig 1). The field was discovered in April 1978 and production started in Feb., 1983. Production is maintained by gas lifting while the pressure is supported by a combined water flooding and limited aquifer drive.

There are 17 producing wells and 4 injectors over 3 offshore platforms. The field is relatively deep reservoir with the original oil water contact at 12350 ft-tvdss. Heavily saturated reservoir with initial reservoir pressure of 5632 psia and the bubble point pressure 1200 psia. The structure contour map Fig (2) shows the reservoir complexity.

The reservoir is a massive sandstone and classified initially as one body of sand. The macro layers were defined from top to bottom as follows; Raha, Nubian III, IIB, IIA and Unit I. Unit IIA has a shale/sand streaks that work as a vertical hydraulic barrier between the upper and lower units.

Fluid flow in the reservoir is directed from unit I to the juxtaposed upper reservoir units supported by water injection in unit I from injector A3b and direct aquifer support. Fluid flow in upper units of block A is only supported by the water injection through injectors A2, A1 and A9 respectively. Fig (3) illustrates the main cross section for the field.

Due to the nature of the of the Ras Budran reservoir and its dipping structure, peripheral injection pattern was proposed and implemented in the original field development plans in October 1985 through two wells A2a (Unit IIB+III+R), and A3b (Unit I). In January 1990, the system was upgraded with another injector A1 (Units IIB+III), to replace the poor injector A2a and finally, the last injector A9a (Units IIB+III+R) was brought on line in April 1992.

The difference between formation and injection seawater salinity was used as a tool to monitor the flood front and the interblock communication. The field has already produced 80% from the estimated reserves.

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