A multilevel U-tube sampler for subsurface environmental monitoring

Sampling fluid in boreholes is always challenging from the standpoints of maintaining integrity and minimizing contamination. This paper focused on the U-tube sampling technology. Firstly, according to initial development motivation, briefly comparison was conducted with available fluid sampling technologies based on driving forces and sample quality. Then, the development history of the U-tube sampling technology was introduced, as well as a comprehensive investigation of its site applications around the world. In particular, a novel multilevel U-tube sampler was designed in China specifically for shallow subsurface, and it had been proven both technically reliable and economically feasible in several carbon capture, utilization, and storage (CCS/CCUS) projects, including the Shengli CO2-enhanced oil recovery (CO2-EOR) project, the Shenhua CCS demonstration project, and the Jilin CO2-EOR project. Finally, the benefits, drawbacks, and future developments of U-tube sampling technology were pointed out as a conclusion. The U-tube sampler used in shallow subsurface is quite suitable in dedicated monitoring projects which specifically require three-dimensional tracing and accurate fluid analysis in a long term.