Multiphase flow and transport processes in the subsurface environment are pervasive in natural and engineered systems, for instance, the geological storage of carbon dioxide and nuclear waste, exploitation of conventional and unconventional oil and gas, geothermal reservoir engineering, fate, and transport of underground contaminants.

A better scientific and engineering understanding of these processes is critical to improve the production of earth’s energy resources, safety of nuclear waste disposal, and remediation of contaminated aquifers. However, it is still a challenging problem to understand the fundamental and practical aspects of multiphase flow processes combined with chemical, thermal, mechanical, and biological interactions occurring between fluids and the reservoir rocks. Due to the large computational burden of multiphase models, it is usually difficult to perform parameter estimation, sensitivity analysis, or uncertainty quantification. Modern nonintrusive and sampling-based optimization and uncertainty quantification techniques are needed to handle the challenges.

This special issue aims to include comprehensive review papers as well as original research papers on recent experimental, theoretical, and numerical results and case studies related to complex multiphase flow and transport in the subsurface environment.

Potential topics include but are not limited to the following:

• Multiphase modeling of coupled (thermal, hydrological, chemical, mechanical, biological, and geophysical) processes
• Geothermal reservoir engineering
• Geological carbon sequestration
• Underground contaminant transport and remediation
• Multiphase inverse modeling and uncertainty quantification