Subsurface stratigraphic picks of the Middle-Upper Triassic Shublik Formation, Alaska North Slope

The Middle-Upper Triassic Shublik Formation is the main source rock for Arctic Alaska oil and gas accumulations, including the supergiant Prudhoe Bay field. A revised stratigraphic framework recently has been developed in outcrop for the Shublik and related strata that delineates three large-scale stratigraphic units: 1) the lower clastic (LC) unit, 2) the middle carbonate-chert (MCC) unit, and 3) the upper clastic-carbonate (UCC) unit. The three stratigraphic units were interpreted to comprise five transgressive-regressive (T-R) sequences (LC1, MCC1, MCC2, MCC3, and UCC1). This outcrop-based framework has been extended to the subsurface of the Alaska North Slope using gamma-ray logs from 161 exploration wells. Subsurface stratigraphic picks of the five T-R sequences within the Shublik Formation for each well are documented herein.

中-上三叠统舒布里克组（Shublik Formation）是阿拉斯加北极地区油气藏（包括超大型普拉德霍湾油田）的主要烃源岩。近期针对舒布里克组及相关地层的露头研究建立了修正后的地层格架，该格架划分出3个大型地层单元：1）下碎屑岩（LC）单元、2）中碳酸盐岩-燧石（MCC）单元、3）上碎屑岩-碳酸盐岩（UCC）单元。研究认为这3个地层单元包含5个海进-海退（T-R）层序（即LC1、MCC1、MCC2、MCC3与UCC1）。该基于露头构建的地层格架已借助161口勘探井的伽马测井曲线，拓展至阿拉斯加北坡的地下区域，本文记录了各井中舒布里克组内5个T-R层序的地下地层识别结果。