Reservoir Monitoring in the Development of Marginal Fields: Ivanhoe, Rob Roy, and Hamish

Abstract

ABSTRACT Reservoir management of the Ivanhoe, Rob Roy and Hamish oil fields has been greatly enhanced during the first year of production by the continuous monitoring of bottom hole pressure in the production and water injection wells. By bringing on production and injection wells in a planned sequence the major flow paths within and between the five reservoir units have been identified. Observed changes in reservoir pressure during planned and unplanned production and injection shutdowns have provided further clues to the geological model and reservoir description. Although not all the bottom hole pressure gauges have continued to function throughout the year a very large amount of daily pressure data has been collected. This has been used to modify and update the full field simulation model of the fields. The reservoirs have been shown to be much less affected by intra-field faulting than had previously been feared, and some shaley layers originally considered to be laterally extensive barriers are in fact more local. Because of this, excellent areal and vertical sweep is expected in the Main Piper sand. Recovery from the overlying Supra Piper sand will be less and will require further infill wells. The reservoir model has been used to optimise individual well rates and minimise the risk of premature water breakthrough, and to site wells during the post-production drilling phase. The design reservoir depletion rate of 20 percent of recoverable oil per year has been easily achieved for both the Ivanhoe and Rob Roy fields.