Discovery of high‐quality Cambrian source rocks in China's first 10 000‐m‐deep well
Sen Zhu, Qingwen Tan, Wanyan Lan, Fangkai Liu, Guangyou ZhuAbstract
The effectiveness of source rocks under ultra‐deep burial (depths exceeding 10 000 m) is critical for hydrocarbon exploration. Well SDTK1 in the Tarim Basin penetrated the Lower Cambrian Yurtus Formation at depths of 10 851–10 910 m. The study found that, despite being at an over‑mature stage of thermal evolution, the lower black shales still retain relatively high residual total organic carbon ( TOC ) content, averaging 4.3%, and a hydrocarbon‐generating potential ( S 1 + S 2 , defined as the sum of the free hydrocarbon content ( S 1 ) and the remaining hydrocarbon generation potential ( S 2 ) averaging 3.8 mg/g. Comparison with data from wells LT1, LT3, and XK1 indicates that during deposition of the Yurtus Formation, primary productivity was high and the water column was under anoxic‐euxinic conditions, with local photic‐zone euxinia, which favored organic matter preservation. Well SDTK1 confirms the existence of effective marine source rocks below 10 000 m, extending the lower depth limit of ultra‐deep petroleum systems in the Tarim Basin and providing an important reference for Cambrian ultra‐deep hydrocarbon exploration.