Abstract
This paper describes how after a period of no activity, a waterflood development is rejuvenated. This is achieved through full integration from geosciences, reservoir engineering and drilling to facilities engineering, operations and surveillance. This collaboration enabled further development following improved subsurface understanding based on appraisal, surveillance and production data as well as managing integrity and capacity issues of the aging facilities.
The Shuaiba limestone reservoir is situated in a fault-bounded, north-south trending anticline. The reservoir (~26% porosity with low matrix permeability, 1–20 mD) contains light oil (~35 API) in thin column heights of typically 5 to 30 m.
In the initial development phase the reservoir was developed by multilateral horizontal producers. Field-wide water injection started ~10 years after initial production with horizontal water injectors placed in multi-lateral patterns of up to 7 legs. The complexity is not limited to the subsurface; surface facilities handle oil-water separation from deeper reservoirs as well as 7 satellite fields.
After years without drilling activity, appraisal wells were recently drilled outside the field extent to test both structural and saturation models with the FWL progressively deepening towards the flanks by approximately ~5m tvd per km. This has added the opportunity of new flank developments to the existing field with significantly increased reserves. New insights into mobile saturation have driven the production threshold down to as low as 25% oil saturation.
The flanks will be developed with single lateral wells, taking into account the thin oil column and optimizing surveillance opportunities.
Challenges facing this development are related to maintaining the aging facilities, integrated management of flow line replacements, overall production capacity and water injection constraints. These are tackled in an integrated manner through (1) debottlenecking the main station and reducing flow line length through remote manifold stations, (2) prioritized flow line replacements ranked by surveillance activities, (3) rejuvenating the water disposal system and (4) restoring the overall downhole injectivity. These combined efforts will expand production far into the next decade.
