The more than 400 known examples of giant dyke swarms on Earth, Venus, and Mars have unique geometric fingerprints with previously untapped potential to provide unique insights into conditions that governed emplacement. These conditions are important for understanding how our own ever-changing planet as well as for comparing the extent to which Earth analogues apply for understanding processes on Venus and Mars. Additionally, the mechanisms leading to these magnificent naturally-occurring systems of fluid-driven cracks may hold a key for drastically reducing the negative environmental impacts of the oil/gas production via geologically-inspired, high efficiency approaches to reservoir stimulation and development. Realizing these goals requires mechanical insights on the mechanisms leading to self-organization and emerging geometric features of dyke swarms. 

 
The goal of this project was to discover the mechanisms that lead to self-organization, and in particular emergent length scales governing dyke/fracture spacing, width, and length, within groups of dykes/hydraulic fractures. Drawing on the framework of swarm theory as developed in the biological sciences, the project aims to clarify the origin of the alignment, repulsion, and attraction forces within these systems and to demonstrate how the interplay of these forces leads to emergent length scales that provide a lasting and measureable imprint of the mechanical conditions governing emplacement. 

 
The merit of the work is illustrated through three main achievements, each of which is associated with unique broader impacts. These accomplishments and their impacts begin with the fact that this work led to the first laboratory confirmation of complex interaction among fluid-driven cracks wherein fractures can sometimes be suppressed by their neighbors and, in other cases with specific non-uniform spatial distribution of fractures, they can interact in such a way that all fractures grow . This discovery inspires a new direction of R&D for industrial hydraulic fractures seeking non-uniform spacing in order to promote uniform stimulation without resorting to energy-intensive methods that promote uniformity of fracture growth by increasing the inlet friction. This method could lead to reduction in water and energy consumption associated with oil/gas recovery by 20% or more.

 
The experiments and simulations demonstrate that emergent spacing scales with fracture height, and this behavior is robust for a wide range of emplacement conditions including one-at-a-time (sequential) and many growing together (simultaneous) emplacement . This discovery implies that spacing is a "fingerprint" of the intrusion conditions, and therefore can be used as a fundamental metric for matching portions of dyke swarms that have been separated by movement of tectonic plates on Earth and enables comparison of emplacement conditions among Earth, Venus, and Mars via study of the emergent dyke spacing within swarms on each of those planets. 

Finally, while the importance of rapidly-computing Reduced Order Models (ROMs) for fluid driven cracks (dykes, hydraulic fractures) has been recognized for decades, this project has put forward 3 of the first examples for multiple interacting fractures. Because of these developments, simulations that used to require days to months of computational time are now available in seconds to minutes. Availability of such rapidly computing models opens doors to new possibilities that hinge on the ability to run thousands of simulations in a short period of time. These include finding conditions at the time of dyke swarm emplacement that give a best match between predictions and observations as well as searching for new ways to stimulate oil/gas wells at a fraction of the economic cost and environmental footprint compared to current practice.

Last Modified: 04/29/2021
Modified by: Andrew Bunger