Many of the once prolific North Sea reservoirs have been reduced to mature assets, with a majority having reserves down to a fraction of their initial value. A significant number of isolated pockets of hydrocarbon bearing sands, however, remain available for production. The advantage of pursuing such bypassed assets is the availability of an existing infrastructure to support any incremental production. The biggest challenge when considering production enhancement initiatives is the marginal nature of the associated economics combined with project risk. In addition, marginal and mature assets seldom generate required engineering firepower to solve complex problems. Lack of investment results in decreased production and downward spiral that only can result in often-premature field abandonment. This paper describes how Marathon identified a requirement for an alternative commercial arrangement and together with a selected service company, built an effective team that rejuvenated a dwindling gas asset. An inter-disciplinary study was initially undertaken to quantify and manage economical risk associated with this project. Previous attempts at rejuvenating production were revisited to assess reasons for their ineffectiveness, or success. An alternative commercial model was then applied to help overcome the marginal nature of the economics. A data acquisition campaign was subsequently undertaken to determine the optimum intervention alternatives. Successful execution of the intervention activities has delivered a two-fold increase to total field production. Several recently introduced technologies were employed during the course of the project. The project also spawned multiple field practices. Their conceptualization, field implementation and long-term effects on production are also described. This paper will present the application and results from several initiatives, including:
Descriptions of an alternative commercial model, where the operator and service company mutually participate in the project risk, and its rewards.
Implementation of the lift-log procedure, a single trip, combined, coiled tubing N2-lift and production logging operation.
Utilization of scale-inhibitor impregnated proppant. This specialized proppant prevents loss of conductivity due to scale deposition within a fracture.
Technical, commercial and operational best practices for use with mature field rehabilitation projects.