LIDAR-ENHANCED FACIES, ARCHITECTURAL, AND STATISTICAL ANALYSES OF A POTENTIAL PALEOCENE RESERVOIR: THE PRINCE CREEK FORMATION AT SAGWON BLUFFS, NORTH SLOPE, ALASKA

The Paleocene Prince Creek Formation (PPC) exposed in 40-120 m-high bluffs along the Sagavanirktok River at Sagwon Bluffs provides an ideal outcrop analogue for a shallow petroleum reservoir on Alaska’s North Slope. Coastal plain facies of the PPC include fine-grained to conglomeratic sandstone, organic siltstone, carbonaceous shale, organic mudstone, and coal deposited in meandering streams, lakes, swamps, and on levees, crevasse splays, and floodplains. Isolated channels encased in thick, organic-rich, muddy floodplain facies suggest high subsidence/accommodation during the Paleocene in this part of the basin.

The first-ever ground based LiDAR survey on the North Slope took advantage of laterally extensive, near-vertical exposures and diverse facies at Sagwon Bluffs, returning high-resolution 3-D spatial and intensity data. The dense sampling of lithologies using LiDAR allows for detailed investigation and correlation of rock properties over survey distances. Spatial relationships inherent to the LiDAR dataset allow for precise measurement of channel length, height, and cross-sectional area with decimeter scale accuracy. Intensity returns (power returned / power emitted) coupled with ground-truthing of facies are used to identify lithologies, produce pseudo-gamma ray logs, and improve net-to-gross calculations. Statistical analyses of intensity returns indicate a roughly trimodal distribution. Ground-truthing suggests that each mode represents a separate, unique lithology. Cumulative probability of lithology vs. intensity plots indicate that intensities of 255-180 represent sandstones, 180-95 represent mudstones, and 95-0 represent coal. Pseudo-gamma ray logs were produced for 14 vertical data slices from height vs. intensity plots at locations lacking scree and containing “clean” outcrop. Model net/gross calculated for each slice provides an improved estimate relative to calculated net/gross from stratigraphic columns. Rare North Slope outcrop belts located near known hydrocarbon accumulations offer a glimpse into facies, alluvial architecture, sandbody geometries, and stacking pattern that is difficult to resolve from seismic and core alone. Analysis of LiDAR datasets from these outcrops will improve geospatial models, reduce risk, and increase production.