First Discovery and Significance of Liquid Mercury in a Thermal Simulation Experiment on Humic Kerogen

Abstract

We found for the first time enriched liquid mercury beads in a thermal simulation experiment on humic kerogen extracted from coal, which provided some kind of direct evidence that mercury can be released from coal measure during maturation. In the simulation experiment, mass distribution of liquid mercury beads is between 0.0083 and 0.2242 g; their content in simulated gas ranges from 372.5 to 2776.3 ng/m3; and their yield was from 0.3102 × 10–3 to 7.4312 × 10–3 g/g sample. Along with this thermal simulation experiment and previous studies, three genetic models of mercury in gas reservoirs are summarized: source-rock controlling type, fault-controlling type, and source-rock/fault joint controlling type. Mercury in source-rock-controlling gas reservoirs is mainly derived from source rocks, which are generally coal measures. Mercury in fault-controlling gas reservoirs is mainly derived from deep geologic fluids, with relatively small contribution from source rocks. The transitional source-rock/fault joint controlling type mainly develops in tectonic activity zones where source rocks can be either sapropelic or humic. Liquid mercury collected for the first time in a simulation experiment has important theoretical significance for the exploration and development of natural gas, as well as important practical significance for the prevention of mercury accidents in natural gas exploration and production.

Mercury Isotopes in Shale Gas From Wufeng-Longmaxi Shale Formation of Sichuan Basin, Southern China: A Preliminary Investigation

“…Ma et al (2020) conducted hydrocarbon-generating thermal simulation experiments on shales and graptolites with different maturities in the upper Ordovician and lower Silurian and found that hydrocarbon-rich and fat-rich organic matter such as algae and acritarch are the main organic matter for shale gas generation. With an increase in burial depth and formation temperature, mercury in the complex and adsorbed state of algae organic matter gradually desorbed under thermal action and migrated to oil and gas reservoirs or oil reservoirs in the form of steam (Peng et al, 2019). Therefore, the Δ 199 Hg information in shale gas and the Δ 199 Hg of the main hydrocarbon-forming organic matter-algae (0.17‰-0.64‰, with an average of 0.39 ± 0.21‰, n = 4,1 SD) (Perrot et al, 2012;Tsui et al, 2012)-showed no significant difference (t-test, p > 0.05) and all values are positive, which also indicates that Δ1 99 Hg in marine crude oil is similar to that of algae.…”