Introduction to this special section: Subsurface uncertainty

Handling the nonuniqueness and ambiguity of geophysical inversion results is a major challenge in characterizing the subsurface. Geophysical inversion is the process of estimating the physical properties of the subsurface from the measured geophysical data, such as seismic, electromagnetic, gravity, or magnetic signals. However, there are often many different subsurface models that can fit the same data adequately well. Therefore, it is important to evaluate the uncertainty and reliability of the inverted models and integrate other sources of information, such as geologic, petrophysical, or geochemical data, to reduce uncertainty. Despite the industry's advances in recent decades, the number of subsurface outcomes that fall outside predicted ranges is disproportionate to the supposed certainty of those ranges. This leads to inefficient allocation of investment budgets, which is particularly painful due to the capital-intensive nature of the oil and gas industry.