Detecting H2 degassing events related to serpentinization in Oman

Peridotite alteration via serpentinization has been identified as a major potential sink of man-made carbon. Peridotite serpentinization provides a geochemical pathway to store CO2 as a solid, and releases natural hydrogen as a byproduct. Given the large quantities of peridotite available in oceanic environments, serpentinization could serve as a major component in mitigating man-made climate change. “Reaction driven cracking” has been proposed as an attractive mechanism to explain how peridotite is fully serpentinized.  In this process, when the peridotite alters and becomes a serpentinite, the volume of the rock grows producing stress on the surrounding rock. This process produces new fractures that allow water to enter new areas within the rock thus promoting new serpentinization. Cracking events due to this fracturing process being driven by peridotite alteration have never been detected in the environment (e.g., seismic data). As part of the Oman Drilling Project, a network of 12 hydrophones was deployed in two boreholes drilled in Oman over a period of nine months. This network was designed to detect the microseismic cracking events associated with reaction driving cracking. Surprisingly, it has served as an excellent detector of natural hydrogen degassing events. Hydrogen is a byproduct of the geochemical serpentinization process. These intermittent events come in short “spurts” where periods of quiescence alternate with short periods where many bubbles come out all at once. This poster presents evidence of hydrogen degassing events related to active serpentinization in Oman. We use the results to provide estimates of hydrogen released during the period of hydrophone deployment based on estimated bubble volumes.