A poro-elastic model for triggering of production-induced earthquakes in the Groningen natural gas field by abrupt changes in well rates

Over the past decade, a steep increase in the number of seismic events has been observed in the Groningen gas producing region of the Northern Netherlands. It is generally accepted that these are induced by compaction of the reservoir rock due to extensive field depletion, causing a buildup of strain energy which may be released seismically when a critical stress level is reached. This study focuses not on the long term compaction, but rather on the possible triggering of fault slip by the transient flow regime surrounding a well which has undergone a sudden rate change. Assuming a unilateral decoupling between displacement and pressure, numerical experiments are conducted using a sequential finite volume-finite element solution strategy that fully incorporates second order terms in the radial flow equation. Solving for short time scales, a spatial and temporal maximum in slip-promoting stress is observed and explained physically. Although present, the transient effect is of a magnitude that raises questions about its significance, especially as the geometric irregularity of a fault with nonzero displacement causes even greater stress concentrations that grow monotonously in time.

Subject

porous media
natural gas
reservoir engineering
poroelasticity
induced seismicity
transient flow

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master thesis

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