Subsurface Structure and Nature of Gas Production and Entrapment of Upper Ordovician Queenston Formation, Auburn Gas Field, Cayuga County, New York
Scott T. Saroff
Geophysical well-log analysis of 111 wells of the Auburn gas field has shown that the Upper Ordovician Queenston Formation contains a range of 6 to 156 ft (cumulative vertical) of 10% and greater apparent porosity, and 9-141 ft (cumulative vertical) of 75% and greater sand content. Permeability measurements made by others range from 1 md to as low as 0.01 md. Rapid initial gas production decline during the first three years of production and sustained long-term low daily and cumulative production confirm geophysical well log and petrographic interpretations that the Queenston Formation is a well-fractured, low-permeability reservoir.
In 1986, 139 wells produced almost 1 bcf, with an individual well average of 19 MCFGD. Fifty percent of the wells in the field produced less than 60 mmcf of gas over the first 7 years, whereas 18% produced over 100 mmcf. The better producing wells were located in areas of higher sand content and, more importantly, within fractured zones. The trend of the better producing wells lies parallel with Precambrian basement faults trending N50°E, interpreted from Bouguer gravity anomaly and aeromagnetic maps. The structurally high trend in the field and the coincidence of better producing wells parallel with these basement faults suggest post-Silurian basement faulting and tensional fractures along hinge lines of drape folding in the Queenston Formation homocline. The entrapment mechanis is a permeability pinch-out in the Queenston deltaic complex to the north, northwest, and west. The capping mechanism is the low-permeability Grimsby siltstone.
AAPG Search and Discovery Article #91031©1988 AAPG Eastern Section, Charleston, West Virginia, 13-16 September 1988.