Development of a tight gas reservoir by a multiple fracced horizontal well: Ameland-204, the Netherlands

Abstract

Poor productivity of a number of tight Permian gas reservoirs is a major constraint on field development in the Dutch offshore sector. In several fields economic development of Rotliegend reservoirs could not be achieved with conventional development techniques due to very low flow rates of less than 200 000 m³/day. This case history covers the Ameland field in the Dutch North-Friesland concession area. The flanks of this layered reservoir can in general be classified as ‘porous but tight’. The geological causes are poor sand facies development and pervasive clay mineral diagenesis, which affected the pore connectivity, resulting in significant untapped reserves. To improve this reservoir performance multiple-fracced horizontal well (MFHW) technology was applied. The project was approached in an integrated manner. The key problems addressed were: 1) verification of sufficient GIIP (gas initially in place); 2) modelling of reservoir architecture; and 3) analysis of productivity improvement by multiple-fraccing technology. The success of the project was confirmed when the MFHW well achieved economic gas production rates (transient) in the order of 2 × 10⁶ m³/day at 120 bar drawdown from this tight Rotliegend gas reservoir. The experience gained and the positive results indicate that multiple-fraccing of horizontal wells may be applicable to other tight gas reservoirs and could raise them from uneconomic prospects to potentially profitable developments.