INTEGRATION OF CORE, LOG AND TEST DATA TO IMPROVE THE CHARACTERISATION OF A THINLY BEDDED RESERVOIR

Low resistivity, thinly bedded formations are typically less than a foot thick and are usually below the resolution of traditional logging tools. This paper discusses the improved characterisation of such formations by using routine and special core analysis data, wireline logs, well test data, core NMR measurements and FMI images. A variety of water saturation models (Archie, Indonesia, Waxman-Smits, Simandoux) were used and comparison of the results demonstrated that water saturation in low resistivity sands was high (approximately 60-85%). The issue of resistivity log resolution was not investigated. The results from well testing showed that dry gas was produced from a ‘wet’ interval. Subsequent NMR analyses showed that the water saturation was high due to a large volume of clay and capillary bound fluid that was immobile during production. Capillary pressure measurements also suggested high irreducible water saturation.