Reservoir Properties of Fluvial‐Lacustrine Triassic Sandstones in the Newark Basin

ABSTRACT Reservoir quality of Stockton Formation (Triassic) fluvial‐lacustrine arenites was investigated by calibrating a porosity petrophysical model for the Princeton 1 core hole, drilled on the hinged limb of the basin half‐graben, and then applying the model to two deep wells drilled on rider blocks downthrown to the basin‐bounding escarpment fault in the axial depocenter. Core plug measurements of porosity, permeability, and grain density were used to calibrate a petrophysical model of effective porosity for the Princeton core hole using sonic and density logs. Neutron log measured porosity is typically 2–3× core‐measured porosity, so this study relied on the sonic and density logs to derive in situ porosity. Some density log measurements may be high due to tool error. Core porosity and permeability have a strong exponential correlation, and arkosic and lithic arenites with porosity greater than 13.5% are likely to have permeability greater than 10 mD. In the Princeton 1, 126 ft. of net reservoir is present in the Stockton Formation gross interval (1528 ft.). Although no core data are available for the deep wells, and wireline log quality is poor to fair, no arenites in either of the deep wells exceeded the 13.5% net reservoir cutoff. The low permeability of the fluvial sandstones in the basin axis is confirmed by analysis of the Cabot 1 Drill Stem Test. The data from all three wells are consistent with progressive occlusion of porosity with burial, due to quartz overgrowth cementation. Secondary porosity, resulting from grain dissolution, offsets some of the porosity loss, but there is a net reduction of porosity with burial. Given the lack of evidence for porosity preservation at depth or development of significant secondary porosity, Stockton Formation reservoirs capable of injection, of either fluids or CO 2 , are likely limited to the hinge limb of the Newark Basin.