Ho Tuan A, Wang Yifeng
Geochemistry Department, Sandia National Laboratories, Albuquerque, NM, 87185, USA.
Nuclear Waste Disposal Research and Analysis Department, Sandia National Laboratories, Albuquerque, NM, 87185, USA.
Sci Rep. 2022 Sep 7;12(1):15196. doi: 10.1038/s41598-022-19564-z.
Heavy metals released from kerogen to produced water during oil/gas extraction have caused major enviromental concerns. To curtail water usage and production in an operation and to use the same process for carbon sequestration, supercritical CO (scCO) has been suggested as a fracking fluid or an oil/gas recovery agent. It has been shown previously that injection of scCO into a reservoir may cause several chemical and physical changes to the reservoir properties including pore surface wettability, gas sorption capacity, and transport properties. Using molecular dynamics simulations, we here demonstrate that injection of scCO might lead to desorption of physically adsorbed metals from kerogen structures. This process on one hand may impact the quality of produced water. On the other hand, it may enhance metal recovery if this process is used for in-situ extraction of critical metals from shale or other organic carbon-rich formations such as coal.
在油气开采过程中，干酪根释放到采出水中的重金属引发了重大环境问题。为了减少作业中的用水量和产量，并将同一工艺用于碳封存，超临界CO₂（scCO₂）已被提议用作压裂液或油气回收剂。先前已表明，向储层注入scCO₂可能会导致储层性质发生若干化学和物理变化，包括孔隙表面润湿性、气体吸附能力和传输性质。通过分子动力学模拟，我们在此证明注入scCO₂可能导致干酪根结构中物理吸附的金属解吸。一方面，这一过程可能会影响采出水的质量。另一方面，如果将此过程用于从页岩或其他有机碳丰富的地层（如煤）中就地提取关键金属，它可能会提高金属回收率。
