Storms Consolidated Field, Illinois Basin: Identifying New Reserves in a Mature Area (E & P Notes)

Discovered in 1939, Storms Consolidated field in the central Illinois basin has produced approximately 24.5 million bbl oil, mainly from Mississippian sandstone reservoirs, yet may contain significant remaining reserves. The field produces from a combination structural-stratigraphic trap along the upthrown side of a major normal fault trend. Although the principal reservoir zone, the Waltersburg Sandstone, is mostly depleted, another important interval, the Aux Vases Sandstone, appears underexploited in many parts of the field. Description and analysis of the only continuous core through the Aux Vases has led to the identification of major lithofacies and their characterization in terms of reservoir quality. The Aux Vases appears to represent a series of shallow marine bars separated by nonreservoir areas of siltstone, shale, and shaly sandstone. Log-based mapping of reservoir distribution, plus production and pressure data, indicates significant lateral and vertical compartmentalization of the reservoir. Although insufficient data exist for full-scale integrated reservoir characterization studies, a trend surface analysis was performed on structural information across the field. The results of this analysis were compared with reservoir distribution maps to identify areas for future drilling or recompletion.