CO2-rich springs are widely exposed in the northeast Qinghai-Tibet plateau, which are important natural analogs of CO2 leakage in geological carbon sequestration. Well ZK10 is one of the typical CO2-driven cold-water geysers in this area. The study on the mechanism of periodic eruption of ZK10 can provide a basis for evaluation, precaution, and management of similar CO2 wellbore leakage in the geological carbon sequestration project.
Combined with field monitoring and wellbore-reservoir coupled numerical simulation, the internal mechanism of periodic eruption in well ZK10 was systematically studied by researchers from the Wuhan Institute of Rock and Soil Mechanics of the Chinese Academy of Sciences, Qinghai Provincial Survey Institute of Hydrogeology, Engineering Geology and Environmental Geology, and Jilin University.
According to the research results, the periodic eruption process of well ZK10 is divided into four stages, including pre-eruption, major-eruption, minor-eruption, and post-eruption. Moreover, the eruption is considered to be caused by the transition between different flow patterns of the two-phase flow within the wellbore, and the self-enhancing of eruption and self-limiting of fluid depleted after eruption enables the periodic eruptions to be maintained. Besides, the wellbore diameter, reservoir permeability, thickness and pressure gradient, as well as the CO2 mass fraction in the groundwater have a profound effect on the periodic eruption process.
This study was published in Journal of Hydrology.
This study was jointly supported by the National key R&D program of China (2019YFE0100100), National Natural Science Foundation of China (Grant Nos. 41602255 and 51809259) and the Basic Research Program of Qinghai Province (Grant No 2018-ZJ-785).
Paper Links: Modeling of CO2-driven cold-water geyser in the northeast Qinghai-Tibet plateau - ScienceDirect
Figure 1. (a) Location and surrounding geology of well ZK10; (b) schematic of well configuration and exposed strata; (c) variation in the water level with time within the sinkhole; (d) schematic of the artificial diversion structure and photos of the vent at the marked moments in Figure. 1(c).
Figure 2. (a) The relationship between the gas saturation and drift velocity at (T, P) = (10 ？C, 3 bar) according to T2Well; (b) time variations in the pressure, gas saturation, drift velocity, and phase velocities at the wellhead, as well as the corresponding relationships between the eruption stages, flow patterns, and self-processes.