Evolution of the Field Development Plan of High Permeability Multilayered Reservoir and Optimization of Injection Strategy

Abstract

ADNOC Offshore successfully revamped the field development plan of one of its reservoir in view of the newly acquired data during initial production phase from 5-Spot pattern drive to Semi-peripheral water injection strategy to ensure delay in water breakthrough and improved sweep efficiency. At the first stage, multi-disciplinary subsurface study was conducted utilizing and carefully analyzing all the available data. This lead to the development of the new model that was able to replicate the field current behavior. Study of the several development strategies helped to analyze field behavior with different development schemes. The change in the development strategy from 5-Spot to Semi-peripheral resulted in an increase of plateau length for four years with an increase in recovery of 6% at economic cut-off limit. Due to high productivity of the reservoir, wells were able to produce without any pressure support contrary to initially predicted performance that lead to the reduction in the water injectors and additional oil producers were incorporated in the development plan that would drain the reservoir more efficiently supported by gas lift. As part of further optimization, horizontal injectors were converted to slanted vertical injectors equipped with inflow control valves that provided full control and selectivity of the injected volume that would provide production assurance in such a high heterogeneous and differentially depleted reservoir. To support this change pilot test was performed that proved successful without jeopardizing the injectivity of the reservoir compared to horizontal well. Implementation of the devised project is in progress that marks the importance of the initial production behavior of the field that could lead to a different development strategy. This project is unique in a sense that with all the additional constraints of surface limitations particularly in the offshore environment, this project is on its path of successful completion.