Rejuvenation of Offshore Low Permeability/Fractured Reservoir through Integration of Various Discipline Studies

Abstract This paper discusses how a low permeability/Fractured carbonate reservoir, has been rejuvenated throughout a new robust development plan supported by Pilot wells performance. Previously this reservoir could not reach its full reservoir potential due to gas recycling through the fracture system. The new plan involves developing the area with less fractures, which was identified by innovative techniques using seismic attributes integrated with FMI and PTA interpretations The primary task was to prepare a conceptual discrete fracture network (DFN) model integrating geological, geophysical, reservoir and production data after diligent reconciliation to represent dual permeability behaviour of the reservoir. PTA interpretations, FMI and seismic attributes were the main inputs to create a reliable history matched DFN network model after several iterations. The history matched model provides credibility and confidence in the revised development plan, which was further validated by pilot wells. A thorough analysis was performed on the pilot wells results to confirm the DFN understanding. This reservoir has been sporadically producing for six decades due to various issues related to the reservoir and the surface. The review revealed that this reservoir is naturally fractured with two main types of fractures: 1) diffused fractures 2) large-scale fractures. The fracture density is higher at the crest of the field and declines towards the flanks. Based on these findings, the development strategy focuses on the low permeability area at the flanks through a line drive water injection, postponing the development of the crest part for later stages. To validate this new plan, some line drive water injection pilots were drilled in different parts of the field. The main goal of these pilots was to confirm productivity with long horizontal drains in areas dominated by matrix and to evaluate line drive water injection as recovery mechanism and well spacing. Based on the success of line drive water injection, it was chosen as the main development scheme for long term development. This study conducted a comprehensive analysis that included the most recent discoveries about the reservoir's static and dynamic properties. This has enhanced the understanding of the reservoir based on its previous performance and will be crucial for planning the future strategies.