NEPTUNUS: Novel methods for the Evaluation and Physical understanding of the Transient natUre of iNdUced Seismicity

Timeline: June 2024- June 2028

Given current concerns on activities in the subsurface, it is crucial to know the limits for safe operations of subsurface reservoirs and limit the risk of induced seismicity. NEPTUNUS (DeepNL 2b) aims to understand the transient nature of induced seismicity with a combination of conceptual and advanced physics-based models, as well as state-of-the-art techniques for data assimilation. Using techniques of systems and control this project seeks to develop tools to combine observations and models to estimate the variables and parameters crucial for the occurrence and mitigation of induced seismicity. With this, the ultimate objectives are 1) to provide constraints on the envelope for safe utilization of the subsurface, for conventional and new energy technologies, and 2) to identify which variables need to be monitored to remain within the safe envelope during a project’s lifetime. These results can feed directly into existing or upcoming seismic hazard assessments for future subsurface use.

MIRIS

MIRIS consider three pilot projects in carbonate systems which all experienced low levels of induced seismicity which cannot be explained with conventional models. To understand why noticeable seismicity occurred at these pilot projects, we perform numerical and experimental simulations which include thermal, chemical and mechanical effects of fluid flow, i.e. ensuring we capture the complex heterogeneous nature of fluid flow in a fractured system. The aim of this project is to explain where and why seismicity will occur in fractured geothermal systems, i.e. to gain insight into the complex interactions between the processes inducing stress changes on faults above, in, and below a fractured carbonate reservoir and the subsequent reactivation of these faults.

InFocus (DeepNL)

Timeline: Oct 2019 – March 2025

To estimate and ultimately forecast seismicity, it is thus crucial to estimate stresses and resolve these three aspects and their interactions. However, uncertainties in subsurface conditions, the inherent intermittent occurrence of fault slip, and the limited availability of in-situ observations make it difficult to uniquely describe responsible mechanisms, let alone provide probabilistic estimates of seismicity. In InFocus, we propose to resolve the feedback between these mechanisms through coupling geomechanics, dynamic rupture and two-phase flow on an equation level, rather than by coupling separate models. To do this, we will make use of existing simulation capability developed for subduction zones. An analysis of seismic observations over the Zeerijp area of the Groningen field will be used to calibrate this model and ensure applicability in reservoir-scale studies. We propose a statistical, Bayesian approach in which observations of subsurface variables, such as strain and (pore) pressure, and prior knowledge on physics are used to constrain stress state and parameters through data assimilation.

A scientific basis for production and reinjection strategies to minimize induced seismicity in Dutch gas fields

Timeline: Jan 2020 – Jan 2024

Science4Steer project is a part of the DeepNL NWO program in collaboration with Utrecht University. In this project, we manage to understand the effects of time-varying pressures, stresses, and strains resulting from gas production and (re-)injection in the Dutch subsurface as a basis for operational strategies to minimize the seismic hazard of human activities in the subsurface. It combined a strong experimental program with the development of semi-analytical and numerical schemes to successfully predict these processes and develop schemes to mitigate induced seismicity hazards. project is a part of the DeepNL NWO program in collaboration with Utrecht University. In this project, we manage to understand the effects of time-varying pressures, stresses, and strains resulting from gas production and (re-)injection in the Dutch subsurface as a basis for operational strategies to minimize the seismic hazard of human activities in the subsurface. It combined a strong experimental program with the development of semi-analytical and numerical schemes to successfully predict these processes and develop schemes to mitigate induced seismicity hazards.

Fingerprinting vertical land motion from the earthquake cycle above subduction zones (User Support Programme Space Research - NWO)

We will test our hypothesis that these processes are the same at different subduction margins and that observational differences are driven by differences in margin geometry. We will assimilate uplift/subsidence data for the post-seismic period of the 1964 Alaska earthquake, where modern GNSS time series came online ~4 decades after the event. Question will be to what extent the data assimilation tightens the constraints on parameters and model states in a context where we (may have to) assume that the processes are very similar to other margins. If successful, our new approach can be applied to forecast sea level changes due to the megathrust earthquake cycle.