HEAVY OIL RESERVOIR OUTCROP ANALOG NEAR ESCALANTE, UTAH: ANALYSIS OF A GAS PERMEABILITY DATA SET FOR NON-DARCY FLOW EFFECTS

Gas permeability data were collected during the summer of 2000 with the small-drillhole minipermeameter probe (Dinwiddie et al., GSA Annual Meeting 2000) at a shallow-marine sandstone outcrop (Upper Cretaceous Straight Cliffs formation near Escalante, Utah) that is a natural analog to the Temblor Formation heavy oil reservoir, Coalinga, California (Lorinovich et al., GSA Annual Meeting 2000). These data were collected on 15-cm (6-in) centers along near-horizontal (along-bed) transects and near-vertical (across-bed) profiles within both bioturbated and cross-bedded sandstone facies. Gas permeability measurements along the vertical profiles showed more variability than those along the horizontal transects, and measurements within the cross-bedded facies were more variable than those within the bioturbated material.

While the new drillhole probe curtails sealing and weathering problems, which are often associated with use of the conventional surface-sealing minipermeameter probe in a field setting, one must still analyze the resulting gas permeability data for evidence of Klinkenberg gas slippage or inertial flow effects and make appropriate corrections, where possible. We discuss the data analysis and correction methodologies for non-Darcy flow effects, and provide a comparison between the uncorrected and corrected gas permeability data and statistics.

Of 111 data locations along a near-horizontal transect within the cross-bedded facies, 32 percent were subject to limited and correctable Klinkenberg gas slippage effects. Additionally, 7 percent of the data locations were subject to correctable inertial flow effects, 10 percent exhibited single-phase Darcy flow, 75 percent exhibited two-phase Darcy flow, and 8 percent lacked enough pressure and flow rate data to determine the presence or absence of non-Darcy flow effects.

Refining the analysis technique herein will support CNWRA confirmatory analyses of similar gas permeability studies at the Bishop Tuff, Bishop, California, which is a Paintbrush Tuff, Yucca Mountain, Nevada analog. This abstract is an independent product of the CNWRA and does not necessarily reflect the views or regulatory position of the U.S. Nuclear Regulatory Commission.