Conventional Techniques

Depth migration

Our depth-imaging capability is built around an integrated set of tools for developing models, and migration algorithms designed to get the most out of your imaging objectives. Our model building incorporates:

  • Use of offset and angle gathers
  • Global tomography
  • Calibration of well velocity to seismic velocity
  • Anisotropy correction

Our migration algorithms include:

  • Kirchhoff ray-based
  • Common azimuth wave equation migration (WEM)
  • Shot-based WEM
  • Beam migration
  • Reverse time migration

Common azimuth 3D depth migration

Common azimuth depth migration is an efficient and accurate wave-equation migration for narrow-azimuth seismic data, such as conventional marine streamer data and FairfieldNodal’s bottom-referenced receiver acquisition. Common azimuth migration offers accuracy approaching that of shot-record migration, but at much lower cost. It can produce images superior to Kirchhoff migration in complicated geological areas such as regions of the Gulf of Mexico containing salt bodies. FairfieldNodal designed its common azimuth depth migration to produce high-quality steep-dip images.

Common azimuth migration also naturally produces angle-domain common image gathers (ADCIGs). Common image gathers show the range of reflection angles, recorded by the acquisition and subsequently imaged, and whether the migration velocity was correct.

RTM
3D angle domain common image gather (ADCIG) at image point "P"

Beam migration

For regions of simple velocity structure, such as above the top of salt, where there is only one ray path linking a surface point and a subsurface point, single-arrival Kirchhoff prestack depth migration imaging is adequate. For regions below the top of salt, when compared to the results of wave-equation migration methods, the single-arrival Kirchhoff algorithm can have degraded image quality in the subsalt. Therefore, FairfieldNodal has developed a common-shot domain, multi-arrival, Kirchhoff beam prestack depth migration that can honor more than one ray path linking a surface point and a subsurface point, to provide higher-fidelity imaging that retains steep dips.

Reverse time migration

FairfieldNodal offers reverse time migration (RTM) as a high-end tool for prestack depth imaging. RTM utilizes the full two-way wave equation, propagating both the source wavefield forward in time, and the receiver wavefield backward (or “reverse”) in time. This algorithm can properly image energy from all arrival paths, without dip limitation, in the presence of significant velocity variations, and in the presence of complex geology. This allows RTM to provide extremely accurate image focusing without limitations. Although this method is computationally intensive, FairfieldNodal’s RTM implementation can produce high-fidelity images in a timely manner.

RTM
RTM

Anisotropy

The development of a velocity field to optimally image seismic data with prestack depth migration often results in a velocity that does not tie the vertical velocity derived at a well. This is due in large part to anisotropic effects in the overburden. FairfieldNodal addresses this problem with its combination of anisotropic model building and anisotropic depth migration algorithms. The model building includes a patented method for calibrating seismically derived velocity models with existing well information followed by three parameter velocity analyses which scan for v0, and the Thomsen parameters: delta and epsilon. We can use the anisotropic model to migrate using our Kirchhoff, wave equation shot migration, and reverse time migration algorithms.

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ZReveal™

Introducing a revolutionary way to view seismic

As part of our ongoing commitment to research and development, FairfieldNodal has developed ZReveal, a new seismic attribute that provides a unique perspective on seismic data by revealing geologic detail at multiple scales.

Unlike conventional attribute processing, this revolutionary, patent-pending technique is calculated in the wavelet domain, using the characteristics of the continuous wavelet transform to correlate seismic data with the underlying geology. As a result, previously hidden, valuable information is brought to light for more confident interpretation.

ZReveal results and input data

ZReveal, computed in the time or depth domain, produces a directionally illuminated topographic-like image.

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  • ZReveal Input
  • ZReveal Output

Benefits of ZReveal

  • Clearer structural and stratigraphic understanding of the subsurface
  • More efficient interpretation of seismic data
  • Multi-scale illumination of geologic features

For more information about this exciting new processing technique, contact John Smythe at FairfieldNodal at 281-275-7500 or email jsmythe@fairfieldnodal.com.

Merging 3D seismic surveys

For decades, oil companies have conducted a patchwork of 3D seismic surveys all over the world. In many areas these surveys partially overlapped or were adjacent to each other. Unfortunately, since these surveys were designed for specific exploration objectives with varying acquisition geometries and orientations, much of the overlapped or adjacent data was ignored during reprocessing. Today, oil companies want all of this information — peripheral surveys included, seamlessly time and depth-migrated onto a common output grid.

In the last few years, we’ve accumulated vast experience successfully merging multiple surveys, both onshore and offshore. We globally and locally address issues of geometry, phase, noise, amplitude, refraction and residual statics to correct for survey-dependent variations. Surveys are output to a common grid, using proprietary techniques to manage offsets, folds and amplitudes for AVO-compliant data.

The results of our approach are outstanding. We’ve already processed over 5,000 square miles of land and transition-zone data and thousands of square miles of OBC data.

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Multi-component processing

Shear wave 3C/9C data for 2D, 3D and 4D projects

FairfieldNodal has been processing 3C and 9C shear wave data for over 20 years, and is one of the few companies to process pure land shear-to-shear data. Our experience includes not just 9C/3D data but several 9C/4D projects, which are becoming more prevalent with increased focus on the dynamic aspects such as CO2 open-fracture flow detection, water floods and pressure changes.

For example, we’ve worked closely with the Colorado School of Mines (CSM) since the late 1980s, developing tools and processing flows to detect reservoir changes. We’ve gone from analyzing fracture orientation and lithology to analyzing the time-lapse aspects of shear- and p-wave data. Recent projects for the DOE involve CO2 sequestration with 9C/4D data.

2D and 3D converted wave data

With the recent increase of high-channel-count land systems and 3C receivers, we have processed many converted-wave 2D and 3D projects—much more difficult than compressional or shear-to-shear data. With our unique tools, we can prestack time-migrate converted wave data, outputting in converted wavetime, p-wave time or shear-to-shear wavetime.

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  • CO2 sequestration 9C/4D project for the CSM and the DOE
    We’ve developed many tools and techniques for separating data from noise in problematic land-shear wave studies. A must for 9C and 3C data processing, these tools have also been a great benefit for extremely difficult land p-wave data or for severely noisy carbonate basins.
  • These two examples show the severe noise effect below the high mesa.
    The noise attenuation achieved from the knowledge gained from years of 9C data processing was critical in merging two 3D data sets.
  • These two examples show the severe noise effect below the high mesa.
    The noise attenuation achieved from the knowledge gained from years of 9C data processing was critical in merging two 3D data sets.
  • Stack with super gather unfolded
    Here, a line from a 3D stack volume with a super gather unfolded to the right reveals an increase in anisotropy due to a change in lithology. The overburdened anisotropy is also seen in the super gather.
  • Fast Radial Slow
    More converted wave processing. In this comparison of radial rotated data to “fast and slow” rotated data, the regional anisotropy was subtle but detectable. Our 2C rotation allowed us to better focus on subtle lithology changes.