Coral Creek Field Study: A Comprehensive Assessment of the Potential of High-Pressure Air Injection in a Mature Waterflood Project

Abstract

Abstract Shell has been producing from the Cedar Creek Anticline (CCA), in the Williston Basin, southeastern Montana, for more than 40 years. Presently, most fields are mature waterfloods with production rates declining between 3% and 8% per year. The producing rocks are low-permeability, non-fractured, porous carbonates that leave waterflood residual oil saturations in the range of 30% to 40%. In order to arrest decline and increase ultimate recovery, a tertiary technology, High-Pressure Air Injection (HPAI), has been considered. Coral Creek Field in the CCA currently produces around 1300 stb/d of oil from the Red River Formation. Due to its size and its relatively low water-cut of 70%, Coral Creek was regarded as an ideal candidate to test HPAI. HPAI is being utilized successfully after primary depletion in other fields in the Williston Basin.1,2,3 However, the technical and economic feasibility of tertiary applications is yet to be demonstrated. A comprehensive field study was undertaken as a prerequisite of such an endeavor. This study integrates all of the geological and production information accumulated during the life of the field, in order to assess the technical viability of tertiary HPAI. The main finding is that under the assumptions of the study, HPAI will not only arrest the production decline, but also double waterflood reserves and current rates in about 5 years.