In the 3rd Phase of redevelopment scheme of the northern part of the Mumbai High Field the focus has been on exclusive development of "U1" i.e. the topmost layer of L-III reservoir, mainly in the western flank area through drilling new wells and side-tracks.

Among the multi-layered accumulation of L-III reservoir, U1 is the most prolific layer with good hydrocarbon facies development in the western flank and holding the highest hydrocarbon in place of L-III. U1 layer is well established in areal extent along the western part of MHN structure bounded by GOC in the east and OWC in the west. Presence of large scale bypassed oil in U1 layer in the western flanks have been appraised through production of infill wells drilled under U1 additional development scheme in the past.

Review of water injection for U1 layer was carried out based on water cut trends and flood front movement in the reservoir. With the help of dynamic production data and saturation maps as generated from simulation model, bypassed oil opportunities were obtained in U1 layer in the western flank. Formation evaluation study based on electro-log records in the nearby wells also showed significant oil saturations in U1 layer. Based on these detailed studies, injector well ‘WI-X’ from WI platform (located in the western periphery of the field) was identified as a candidate for side-track as a horizontal producer in U1 layer. Further, analyzing nearby wells' production vis-à-vis injection scenario the location was optimized and decided to side-track keeping a distance of around 800-900 m away from the flooded area of the injector well ‘WI-X’. This would ensure in avoiding early breakthrough of injection water and optimize the well location in the relatively un-drained area. After side-tracking and initial testing, the well came up with 600 bopd with 70% of water cut. This well has also been completed with intelligent completion with a view to manage water cut in the well owing to its proximity to water injection platform.

The present study highlights the importance of identifying bypassed oil opportunities contained in thin oil layers like U1. It also signifies the importance of application of integrated methodology viz. dynamic production data, simulation model results and well logs analysis to enable a definitive identification of such locations.

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