Five source rock units on the North Slope are identified, characterized, and mapped to better understand the origin of the hydrocarbon charge in each petroleum system: Kuna-Lisburne, Shublik-Otuk, Kingak-Blankenship, Pebble-GRZ-Torok, and Hue Shale. Data from Rock-Eval, vitrinite reflectance, elemental analysis, and well logs are used to map the present-day organic richness (TOC, wt. %), quality (HI, mg HC/gm TOC), thermal maturity (% Ro), and net thickness. To map these units, we assumed that: a) petroleum source rocks contain >=2 wt. % organic carbon (TOC); b) immature oil-prone source rocks have hydrogen indices (HI) >300; c) the top and bottom of the petroleum (oil plus gas) window occur at vitrinite reflectance values of 0.6 and 1.0% Ro, respectively; and d) net source rock thickness is calculated using gross thickness and >=2 wt. % organic carbon for organic matter.
Rock-Eval data for 322 samples from 37 North Slope wells that penetrate the Shublik Formation were filtered using PI (<0.10), Tmax (400-600 ºC) and TOC >=2 wt. %, which left 183 samples to calculate net thickness. Net source rock thickness ranged from 0 to 272 ft with an average of 77 ft. The TOC ranges from 2 to >9 wt. %, with a mode of 3 wt. %. The HI for immature source rock (Tmax 400<440 ºC) ranges from 100 to 900 mg HC/gm TOC , whereas most of the mature and depleted source rock samples (>440 ºC) have <200 mg HC/gm TOC. These present-day source rock richness and quality maps are used to determine the same characteristics prior to reaching 0.6% Ro.