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Seismic Attributes and Direct Hydrocarbon Indicators (DHI)

Competency Statement:

Evaluate seismic attribute sections to enhance conventional seismic interpretation. Identify the seismic effects of a 'bright spot' anomaly and their physical cause. Describe the Amplitude Vs. Offset (AVO) effect and the physics that govern the response. List the attributes of the Hilbert Transform and their mathmatical formulation.

Learning Objective:

  • List possible effects to seismic amplitude response on 'Bright Spot' prospect.
  • Describe AVO response and its causes.
  • Explain the limitations of AVO response.
  • Review Hilbert transform attributes.
  • Describe work flow for evaluating attribute effectiveness.

Assignment Instruction:

Surface seismic is the most important tool for delineating a reservoir. In the past, most of the effort was focused on structural imaging. However, due to the advances in computational hardware and new theoretical approaches to sedimentation processes and wave phenomena, seismic attribute analysis has become a major focus for locating hydrocarbon indicators. AVO, amplitude analysis, frequency decomposition, wave attenuation, and elastic inversion are only a few techniques which transform wave information into hydrocarbon indicators. The following assignment teaches us the importance of attribute characterization.

Your team is working in a gas prone area. Two exploratory wells have been drilled in the area; the first well is located over a structural high and successful and the second is located down dip and dry. Drilling plans and locations for both wells were planned using 2D conventional seismic. A new 3D seismic survey was acquired in order to give a better picture of the gas-water contact distribution. Interpretation uses seismic attributes as hydrocarbon indicators.

The main target is the reservoir discovered by the first well at 4500 depth (2000ms, two way time). Other possible reservoirs might exist at 3500ms and 7000ms. You will use the 3D seismic to extract and analyze seismic attributes; you are responsible from the seismic QC to AVO characterization. You will also make a proposal for the potential reservoirs.