Geophysics - Reservoir Characterization

Microseismic Monitoring in Oil and Gas Reservoirs

 

Instructor

  Dr Leo Eisner (Seismik, Prague, Czech Republic)

Duration

  2 days

Disciplines

  Geophysics – Reservoir Characterization, Reservoir Engineering

Level

  Foundation

Language

  English

EurGeol

  10 CPD points

Keywords

 
 ANISOTROPY   EARTHQUAKE   GEOPHONES   INDUCED SEISMICITY   ISOTROPY   P‑WAVE   POLARIZATION   S‑WAVE 

 

Course description

The goal of this class is to explain principles of microseismic monitoring ranging from single monitoring borehole to surface and near surface networks. This class focuses on understanding the measurements made in passive seismic, their use and their uncertainties. Attendees should be able to decide on the best type of microseismic monitoring, design it, and know what kind of processing is needed to achieve their goals. They will also understand the uncertainties in the microseismicity. They will be able to avoid interpretation of uncertain observations. No requirement on prior class is needed, although knowledge of hydraulic fracturing and seismology helps. The course will also discuss the latest developments in microseismicity from source mechanisms, through tomography and anisotropy to reservoir simulations, including pore pressure analysis. The course discusses also social and scientific aspects of (induced) seismicity related to oil and gas reservoir.

 

Course objectives

Upon completion of the course, participants will be able to:

  • Design an optimal array for passive seismic (surface or downhole) monitoring estimate 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;

  • Indentify 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 oildfield 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. Microseismicity and induced seismicity by reservoir production. Historical review of microseismicity in oil industry with focus on hydraulic fracturing (M-site, Cotton Valley, Barnett, etc). Principles of the hydraulic fracturing and geomechanics. Why do we do microseismic monitoring.
  2. Earthquakes: number of unknowns, differences between active and passive seismic. Absolute location, relative location. P- and S-wave polarizations. Frequency content of microseismic data. Finite source. Earthqauke magnitudes.
  3. Downhole location technique: single well monitoring technique - S-P wave time + P-wave polarization technique location. Single phase location. Horizontal monitoring borehole. Picking strategies for microseismic data. Optimal design of downhole monitoring array. Orientation of downhole geophones. Velocity model building and calibration. Inclined/dual and multi well monitoring.
  4. Surface monitoring technique: 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 - the 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 oil or gas reservoirs. 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 hydraulic fracturing and seismology would be beneficial.

 

About the instructor

Dr Leo Eisner

Leo Eisner obtained his 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 where he filed five patents and issued numerous publications. The 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 joined MicroSeismic, Inc. in 2008 and since 2009 till 2010 he was the Chief Geophysicist. He moved to Prague in 2010 and become Purkyne Fellow at Academy of Sciences of the Czech Republic till 2014. He founded and presides over the consulting company Seismik s.r.o.

 

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