Microseismic Monitoring for the Energy Industry

Course Description

This newly revised programme explaines the principles of microseismic monitoring ranging from single monitoring borehole to surface and near surface networks. The applications cover from conventional to unconventional production, through geothermal energy extraction to CO2 sequestration. We will focus on understanding the measurements made in passive seismic, their use and their uncertainties. The course will also discuss the latest developments in microseismicity from DAS monitoring systems, source mechanisms, tomography and anisotropy to reservoir simulations. Finally, we will discuss social and scientific aspects of (induced) seismicity related to oil and gas reservoir, hydraulic fracturing and unconventional production.

Course Objectives

Upon completion of the course, participants will be able to: • Select the right type of microseismic monitoring array to meet the goals that need to be monitored; • Design an optimal array for passive seismic (surface or downhole) monitoring, estimate in it uncertainties of locations for microseismic events; • Orient downhole geophones from a perforation or calibration shot, estimate approximate distance and depth of a recorded microseismic event; • Calibrate velocity model; • Identify shear wave splitting in downhole microseismic datasets; • Mitigate hazards associated with induced seismicity by fluid injection; • Determine epicenter from the surface monitoring array and estimate source mechanisms of visible microseismic events; • Determine if the seismicity in the vicinity of an oilfield is related to injection or extraction of fluids.

Course Outline

1. Introduction: Definitions, a brief review of microseismicity outside of oil industry: water reservoirs, mining, geothermal, CO2 sequestration. Microseismicity and induced seismicity by reservoir production. Historical review of microseismicity in energy industry with focus on hydraulic fracturing (Basel, Soultz, M-site, Cotton Valley, Barnett, etc). Principles of the hydraulic fracturing and geomechanics. Goal of microseismic monitoring and options to meet them. 2. Earthquake seismology: number of unknowns, differences between active and passive seismic. Receivers - how to select optimal type of sensors to meet our goals. Absolute location, relative location. P- and S-wave polarizations. Frequency content of microseismic data. Finite source. Earthquake magnitudes. 3. Downhole monitoring: single well monitoring technique - S-P wave time + P-wave polarization technique location. Horizontal monitoring borehole. Picking strategies for downhole monotoring. Optimal design of downhole monitoring array. Orientation of downhole geophones. Velocity model building and calibration. Inclined/ dual and multi well monitoring. 4. Surface monitoring: P-wave location from surface: depth vs. origin time. Detection uncertainty and signal-to-noise ratio. Frequency content, attenuation and detection. Design of surface monitoring array. Calibration and velocity model building. Relative locations: using S-waves recorded at the surface monitoring array. Case study comparing the downhole and surface locations. Why surface microseismic monitoring works, near surface attenuation. 5. Source mechanisms: concept of source mechanism, definition of dip, strike and rake for shear source. Description of shear, tensile, volumetric, CLVD components of source mechanism. Inversion for source mechanisms from single monitoring borehole, multiple monitoring boreholes surface P-wave only data. Radiation pattern of source mechanisms frequently seen in microseismic monitoring. Source mechanisms and stress orientation. 6. Advanced source parametrization: Magnitude: definition and determination, seismic energy, b-values and magnitude of completness, physical liminations of b-values, stress drop, source dimensions. 7. Anisotropy: Introduction to anisotropy. Effect of anisotropic media on S-waves: shear wave splitting. Shear wave splitting observed in microseismic data. Inversion of anisotropic media from P- and S-waves using microseismic events, time lapse changes. Anisotropy and surface monitoring of microseismic events. 8. Reservoir simulations: Current use of microseismicity in oil industry and implementation of microseismicity into modeling. Diffusion model for pressure triggering of microseismic events. Non-linear diffussion and mass balance. Discrete Fracture Networks constrained by microseismicity. Reservoir simulations and history matching. 9. Seismicity in the vicinity of energy exploration. History of felt seismicity related to oil and gas industry. Differentiation of natural and induced seismicity. Seismic moment and total injected volume. Blackpool case study as an example of induced seismicity. Oklahoma and DFW seismicity - natural seismicity? Hazard assesment and mitigation. Social aspects related to development of shale gas. 10. Review of recent reserch effort and case studies in microseismicity. Models of relationship between microseismicity and hydraulic fracturing. Most important things to remember about microseismicity.

Participants’ Profile

The course is designed for users and practitioners in microseismic monitoring.

Prerequisites

No requirements prior to the course are needed, although knowledge of seismology and hydraulic fracturing would be beneficial.

About the Instructor

Leo Eisner obtained his MSc. degree in Physics at the Charles University of Prague and Ph.D. in Geophysics from the California Institute of Technology and his M.S in Geophysics from the Charles University in Prague. He spent six years as a Senior Research Scientist with Cambridge Schlumberger Research. He then moved to MicroSeismic, Inc. in 2008 and since 2009 till 2010 he was the Chief Geophysicist. in 2010 he moved to Prague to become Purkyne Fellow at the Czech Academy of Sciences. He worked in the Academy of Sciences until 2017. He founded and he is currently the President of a consulting company Seismik s.r.o. His papers and extended abstracts cover a broad range of subjects, including the seismic ray method, finite-difference methods, seismological investigations of local and regional earthquakes and microearthquakes induced by hydraulic fracturing, etc. He has lead/advised three Ph.D.s and six MSc. theses.