Abstract
The Cretaceous field studied is a low-permeability, heterogeneously naturally fractured reservoir. A critical success factor for development wells, which target areas of enhanced reservoir matrix quality, is the requirement to intercept an extensive network of open natural fractures. Tapping into such a fracture network enables a larger volume of porous matrix to be drained. This article describes new technology to identify (1) areas of enhanced reservoir quality within a thin porous interval (ca. 10m) and (2) areas with a high probability of being extensively fractured. Matrix porosity distribution was derived from seismic attributes and incorporated into 3D static reservoir models. In parallel, fracture permeability maps were determined from stress calculations and subsequently combined with matrix models for dynamic simulation. To validate and select possible subsurface models, rates from all producing wells (that vary by a factor of 10) were history matched with one model that is consistent with available static data. Successful blind tests of the model through reactivation and re-completion of old wells have been carried out by the operator. These have enabled Shell to exceed production targets for 1999 and have significantly increased the probability of success for future development wells. The subsurface modeling philosophy has substantial implications for similar naturally fractured carbonates.