Innovative Approach to Develop an Old Complex Reservoir Bearing Multi-Billion Barrels of Reserves in a Middle-East Carbonate Field

Abstract

This paper showcases the development approach recently adopted in an offshore reservoir bearing multi billion stock tank barrels of oil-in-place that solely depended on natural depletion starting from the year of 1962 until the introduction of the crestal gas injection mechanism in 1994, yet less than three percent of this potential has so far been recovered! This low recovery can be justified by the very complex nature of this reservoir varying from the expected highly fractured crest to the very poor characteristics of the matrix spreading towards the down flank, in addition to the high competition between this as a lazy reservoir and the other high potential reservoirs to produce against a high-pressure system of surface facilities. Even though the very first oil shipment in 1962 from this field was exported from this reservoir, all these surface and subsurface bottlenecks have been making its development so challenging that it had to be put to a halt yielding a hydrocarbon recovery that is less than three percent of its potential in the past 60 years. A new development approach was adopted in this reservoir introducing the line drive water injection mechanism as a basis for all future development, in addition to introducing artificial means in order to overcome the high-pressure system of the existing surface facilities. Several uncertainties were encountered linked to this type of development plan for this type of complex reservoir such as well spacing (OP/WI), well architect (short horizontal vs. MRC/ERD vs. deviated), well completion, well productivity/eruptivity and for water injection as it is the first time to inject water in this type of reservoirs water injectivity, water quality, scale risk..etc. So, a dedicated de-risking plan was introduced & implemented to try to overcome and mitigate all these challenges and risks before full implementation of the proposed development plan. The line drive pilot (OP/WI) plan was implemented mirroring the future long term development plan for the main purpose of proving the economical feasibility of the line drive recovery mechanism in such a reservoir while maximizing the acquisition of associated static and dynamic monitoring data. This will ultimately appraise and feed into the long-term development plan set for this reservoir while paving the way for it to reach its true potential and meet its future production target. This paper discusses both the de-risking pilot design and its results, which overall, support the implementation of this development plan. The pilot was started with the oil producer since Aug-2020 followed by the water injection since Mar-2021.