Calculation Method and Application for Water Content of Paleogene Reservoirs in L Oilfield

Paleogene reservoirs in the L Oilfield have strong heterogeneity and complex oil and water layers, so the conventional techniques for identification of fluid properties can hardly meet the demands of logging evaluation. By using the multiphase permeability flow distribution theory, the water contents of reservoirs can be calculated quantitatively to determine properties of produced fluids accurately. The water content was applied to study the lower limit of oil saturation, combined with upper limit of water content in oil reservoirs, the relationship among water contents, porosity and oil saturation can be determined by using analytical method to obtain the lower limit of oil saturations in different types of reservoirs. The quantitative calculating results for identificating reservoir fluid properties in the L Oilfield have coincidence rates above 90% with that of testing and actual production. The lower limits of oil saturation were determined as follows: 59% for class one reservoir, 48% for class two reservior, and 35% for class three reservoir. In addition, the functional equation of oil saturation lower limit and porosity has been obtained by fitting method, the lower limit of oil saturation was 35% corresponding to the class three reservoir. The application result showed that water content could be used to quantitatively determine the properties of the produced fluids. The lower limit of oil saturation increased at an exponential function with porosity in different types of reservoirs, which could be quantitatively determine the lower limit of oil saturation in different types of reservoirs.