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Exploring for Oil and Gas Traps
Series Treatise in Petroleum Geology
Part Predicting the occurrence of oil and gas traps
Chapter Exploring for stratigraphic traps
Author John C. Dolson, Mike S. Bahorich, Rick C. Tobin, Edward A. Beaumont, Louis J. Terlikoski, Michael L. Hendricks
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Seismic facies are "mappable, three dimensional seismic units composed of groups of reflections whose parameters differ from those of adjacent facies units”.[1] Seismic facies analysis is the description and interpretation of seismic reflection parameters, such as configuration, continuity, amplitude, and frequency, within the stratigraphic framework of a depositional sequence. Its purpose is to determine all variations of seismic parameters within third-order sequences and their systems tracts in order to determine lateral lithofacies and fluid type changes.[2] Of these parameters, reflection pattern geometries are perhaps the most useful for calibration with lithofacies interpreted from well logs, cores, and cuttings.

Control of thickness tuning and frequency tuning on seismic facies. Amplitude and its instantaneous attribute models are calculated with 90° Ricker wavelets of 20-, 35-, and 80-Hz peak frequencies (or 26-, 45.5-, and 104-Hz predominant frequencies, respectively). No noise is added to the convolution models.[3]

Reflection parameters

There are five useful reflection parameters:

Depositional environment, sediment source, and lithofacies can be interpreted by grouping these parameters into mappable, three-dimensional seismic facies.[4] The table below[1] summarizes the information obtained from each parameter.

Reflection parameter Geologic interpretation
Configuration
  • Bedding patterns
  • Depositional properties
  • Erosion and paleotopography
  • Fluid contacts
Continuity
  • Lateral continuity of strata
  • Depositional processes
Amplitude
  • Velocity and density contrasts of individual interfaces
  • Bed spacing
  • Bed thickness
Frequency
  • Bed thickness
  • Fluid content
Interval velocity
  • Lithofacies estimations
  • Porosity estimations
  • Fluid content

Seismic facies analysis procedure

The table below outlines a procedure to analyze seismic facies from a grid of sections (vertical) of 2-D or 3-D seismic data (modified from [1]).

  1. Divide each depositional sequence into seismic facies units on all seismic sections.
  2. Describe the internal reflection configuration and terminations of each seismic facies unit, i.e., sigmoid, parallel, downlap.
  3. Transfer seismic facies descriptions from seismic sections to a shot point map of each sequence.
  4. Combine seismic facies distribution and thickness with the map distribution of any other diagnostic parameters, such as interval velocity or localized amplitude anomalies.
  5. Integrate well and outcrop data with seismic facies distribution.
  6. Interpret the seismic facies maps in terms of depositional settings such as marine or nonmarine, water depth, basin position, energy, transport direction, or any other depositional aspects.
  7. Estimate lithology using depositional setting interpretation from step 6 and all available data.

See also

References

  1. ↑ 1.0 1.1 1.2 Mitchum, R., M., Vail, P., R., Sangree, J., B., 1977, Seismic stratigraphy and global changes in sea level, part 6: stratigraphic interpretations of seismic reflection patterns in depositional sequences, in Payton, C., E., ed., Seismic Stratigraphy and Applications to Hydrocarbon Exploration: AAPG Memoir 26, p. 117–133.
  2. ↑ Vail, P., R., 1987, Seismic stratigraphy interpretation procedure, in Bally, A., W., ed., Atlas of Seismic Stratigraphy: AAPG Studies in Geology No. 27, p. 2.
  3. ↑ Zeng, Hongliu, 2013, Frequency-dependent seismic-stratigraphic and facies interpretation: AAPG Bulletin, v. 97, no. 2, p. 201–221, DOI:10.1306/06011212029.
  4. ↑ Bally, A., W., ed., 1987, Atlas of Seismic Stratigraphy: AAPG Studies in Geology 27, vol. 1, 124 p.

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