Ujjwal Shekhar

Ujjwal Shekhar

Microseismic wavefield modeling using the integral equation method

Induced seismicity is commonly associated with activities like conventional and unconventional oil/gas production, enhanced geothermal systems, carbon sequestration, hydraulic fracturing, etc. Fluid injection/extraction affects the pore pressure within the rockmass and may lead to the reactivation of critically stressed pre-existing faults. Seismic waves are generated at a source that can be associated with a slip on the fault plane. These microseismic events are often considered weak seismic events. However, in the past few years, the occurrence of moderate to strong earthquakes induced by fluid injection (as an example, a magnitude 5.8 earthquake on September 23, 2016 in central Oklahoma: source – USGS) has posed a threat that cannot be overlooked.

Microseismic wavefield modeling is one of the key aspects of a microseismic monitoring project. Microseismic monitoring is a passive technique that involves analyzing the seismic data gathered over the region of interest to detect such events. It is necessary to characterize and locate microseismic sources in order to avoid any risk of environmental hazards and damage to the infrastructures. The main goal of this work is to demonstrate seismic wave propagation in elastic media due to different types of microseismic sources. Using the fundamentals of scattering theory, the elastodynamic wave equation is formulated as an integral equation of the Lippmann-Schwinger type. The Fourier transform-based iterative solver is implemented to obtain the wavefield in an efficient way. The numerical scheme is applied to anisotropic and heterogeneous models with the purpose of investigating the applicability of the method in complicated geological scenarios.