Irreducible Water Saturation Determination and Fluid Identification Methods in Carbonate Reservoirs: A Middle Eastern Case Study

In the H oilfield, there are many technical challenges in the effective fluid identifications of carbonate reservoirs with complex pore structures and diversified reservoir spaces when water flooding problems occur in the oil wells during early period of the oilfield production. Based on the Archie formula, the formation resistivity is used to perform the mathematical differential calculation of water saturation and porosity. The results of irreducible water saturation were used to calibrate the oil zone discriminant lines, and the aquifer discriminant lines were calibrated when the water saturation was 100%, allowing for a novel reservoir fluid property identification method. An important parameter involved in this method is the irreducible water saturation. The irreducible water saturation of cores is determined by using a lot of MICP data, and sensitive conventional log curves are selected to construct the irreducible water saturation curve of each well with machine learning training method after the correlation between conventional logs and irreducible water saturation of cores is analyzed. This total differential method can effectively identify the water zones, oil zones and transition zones. In addition, the original formation resistivity curves of production wells in the development areas are constructed with machine learning training while the exploration wells before production are selected as sample wells. Compared the original formation resistivity with the measured deep lateral resistivity, the reservoir fluid types can be well identified. When combined two methods are first applied in the fluid identification of carbonate reservoirs, the identification results were in good agreement with production and test data with an accuracy rate of more than 85%. At present, these methods are programmed and linked to the professional software platform to obtain a good application effect in the H oilfield.