Best RM Practices for Managing Drilling Margin: A Deepwater Field Experience

Abstract

In the buildup to the drilling campaign in Agbami, the field encountered disruption in its gas injection capability due to hydrate formation in one of the gas injection manifolds. In addition to this operational challenge was a delay in the arrival of the rig. The impact of these two major issues was higher depletion in reservoir pressures in the field than originally planned, with the attendant narrow drilling margin. This narrow drilling margin posed a significant challenge to the success of the drilling campaign. A multidisciplinary team comprising of Reservoir Engineers, Geologists, Drilling and Completion Engineers collaborated to assess the potential impact of these two issues on forthcoming drilling campaign. The team found out that the shallow reservoirs of the field were most impacted. The team then evaluated multiple options for addressing the foreseeable pressure depletion with its attendant drilling margin challenge. Leveraging the stream of downhole surveillance data from the intelligent completions in the field, reservoir simulation model was used to assess the optimal production and injection rates for the reservoirs, in addition to the priority given to the limited available gas and water for injection into the identified reservoirs that will boost pressure adequately prior to commencement of the drilling campaign. Furthermore, rig schedule optimization was carried out to align the well drill dates to those from the reservoir simulation. This joint effort resulted in improved reservoir pressures in the shallow reservoirs that enabled safe drilling margin during the successful drilling campaign.