Geochemical studies of reservoir processes in the NCPA field of The Geysers, a preliminary report

Methods of tracing reservoir processes will be discussed and applied to the NCPA Geysers steam field. The gas and isotope chemistry of produced steam is far from uniform even in a restricted volume of the reservoir. The composition is affected by many factors. Differences in permeability, local existence of gas pockets or perched liquid and the pattern of fracture connection can cause neighboring wells to produce steam of different compositions. This study attempts to separate local effects from general influences by viewing the data across the field and over a period of time. The fits of the trend lines to the data are far from perfect but present a reasonably consistent picture