Petroleum Geophysics Short Courses

graduate

 

Petrobras V - Electromagnetic Geophysics for Petroleum
  Instructor Tuition

Dr. Kurt Strack; Dr. Leon Thomsen
University of Houston

$1000

Course description

Electromagnetic techniques are important for hydrocarbon E&P because they can distinguish between oil and water saturated rock, responding directly to water-filled porosity. Their strength lies in their complementary use, along with seismics, either to improve the seismic velocity interpretation or to provide additional information such as inferred porosities and hydrocarbon content.

We will introduce three techniques: Magnetotellurics (MT), frequency domain Controlled Source ElectroMagnetics (f-CSEM), and time domain CSEM (tCSEM™). MT uses the Earth's natural electromagnetic field as its source, and makes vector measurements (of the electric and magnetic fields) to obtain information about the resistivity structure. CSEM uses its own transmitter, also with both magnetic and electric field measurements. Each technique has an optimum depth range, which depends on the resistivity environment, with some overlap between the methods.

When optimizing the recovery factor of hydrocarbon reservoirs, integration between borehole measurements and surface measurements is crucial to understand the scale limitation of the surface data and also the limitations of borehole data, as it is used for calibration. A better understanding of the influence of the rock properties leads one to select the appropriate Earth model. Borehole EM tools are then designed to measure the parameters of such Earth models, and to get a better insight into the reservoir.

Numerous case histories are shown where MT, CSEM, and tCSEM™ measurements confirm independently other measurements and help in getting better resolution in the interpretation. The applications range from hydrocarbon exploration, geothermal exploration, sub-salt exploration, and deep crustal studies. MT is widely used in many parts of the world for a variety of applications, e.g. for oil exploration in seismically difficult areas, such as beneath karsts and salt. At 'audio' frequencies it is used for mineral exploration at depths beyond the reach of Transient EM while, at still higher frequencies, it is being applied to a range of environmental problems. CSEM results are more closely held by oil companies, but enough is available to indicate the advantages and limitations of the techniques

The future of electromagnetic measurements lies clearly in their combination with reflection seismics, to better define fluid content, and to constrain the interpretation of seismic velocities.


Topics

  • Electrical properties of rocks
  • EM fields: MT, CSEM – 1D
  • MT processing
  • CSEM: TEM
    • Processing
    • Inversion
  • Marine CSEM
    • Frequency domain
    • Time domain

EM applications and case histories

  • Feasibility studies
    • 1D, 3D
  • Case histories
    • MT case histories
      • Sub-salt imaging: Wedehof
      • Geothermal: Iceland
    • Resolving resistive layers
    • India, China examples