Nitrogen isotopes of released gas from rock crushing and implications to origins of molecular nitrogen in Lower Cambrian overmature shale gas in South China

Both methods—high-vacuum-pulsed electromagnetic rock-crushing and degassing and helium-filled ball-mill rock-crushing and degassing—are developed to measure the contents, chemical compositions and nitrogen isotopes of N2 in shale-crushed gas from Lower Cambrian organic-rich shales in South China. Using the shale-crushed gas geochemistry, thermal maturity, mineral composition and nitrogen species of the Lower Cambrian overmature shale, we examined the key factors causing N2 enrichment in the Cambrian shale gas, and we investigated the origins of N2.

本研究开发了两种实验方法——高真空脉冲电磁破碎脱气法（high-vacuum-pulsed electromagnetic rock-crushing and degassing）与充氦球磨破碎脱气法（helium-filled ball-mill rock-crushing and degassing），用以测定中国南方下寒武统富有机质页岩（Lower Cambrian organic-rich shales）经破碎后释放气体中氮气（N₂）的含量、化学组成及氮同位素。通过分析该下寒武统过成熟页岩的页岩破碎气体（shale-crushed gas）地球化学特征、热成熟度、矿物组成及氮物种，本研究厘清了寒武系页岩气中氮气富集的关键控制因素，并探究了氮气的成因来源。