Estimates indicate that global EOR target oil in the world's currently producing fields and expected future discoveries, is well over 5000 billion stock tank barrels. Expected recoverable reserves from this target oil, through the application of enhanced oil recovery (EOR) technologies, could range from 1600 to 25 l0 billion barrels. However, the spatial distribution of the reserves need to be confirmed through the application of quantitative oil saturation measurement techniques.
This paper discusses the techniques of EOR target oil estimation. These techniques are broadly of geological and reservoir engineering nature which can be conveniently classified into: (a) field techniques, (b) laboratory techniques, and (c) material-balance/reservoir performance.
In the material-balance methods, remaining oil saturation, ROS, can be determined from production history data/records, whereas field techniques include coring, well logging and well testing; and laboratory techniques include core analyses, fluid analyses and dynamic flow experiments. These different techniques do not necessarily produce the same results; therefore, understanding the limitations, accuracy and sources of errors of the different measuring techniques is critically important in selecting a particular technique (or techniques) for an economic enhanced oil recovery project.