Abstract
A large brown-field in South Oman showed decline in production despite moderate level of in-fill drilling over the last few years. The field has four major reservoirs distributed across three stratigraphic horizons and contains moderate to highly viscous oil (60 to 400 cp). The reservoirs comprise unconsolidated fluvial, fluvial deltaic and glacial sandstones of Palaeozoic age. The geologically complex field due to large number of faults and fractures has been on production for more than 25 years and has been developed using vertical and horizontal wells during different phases of development. Water-flooding is in operation in two of the major reservoirs for more than 5 years. Well and Reservoir Management in this field poses a formidable challenge due to:
Significant well-stock (more than 450 wells) of different types (vertical, horizontal, multi-lateral)
Problem associated with data acquisition as all the wells are completed with pumps (beam pump, progressive cavity pump and electrical submersible pump) and most of them are completed with some sand-control device
Water-flood management under very adverse mobility conditions in presence of faults and fractures often resulting in premature breakthrough of injected water
Logistical problems associated with large distance between the Well and Reservoir Management team at corporate office and the operational team at field location.
The case study presented in this paper describes how a sustained well and reservoir management strategy implemented across the entire value chain starting from the planning to operation stage in this field could not only arrest but literally reverse the field production decline trend using the existing well stock. The paper clearly illustrates that success of reservoir management rests not only on the application of right technology but more on close integration among various disciplines in a cohesive work environment.
