Services

Log Reconstruction (for Synthetic Seismograms)

Synthetic Seismograms are the key to proper seismic interpretation and analysis, yet most synthetics do not tie, due to problems with the well-logs. Missing logs can be constructed, and errant logs identified and corrected, if the log curves exhibit dependable relationships. Our method involves identifying the best-quality zones, then using their data to derive the relationships. Each curve can then be computed from other curves. The recorded data is retained where it differs little from the computed. Our people, not computers, make all judgments of data quality. At the end of the job, a network of cross-checks is performed, and if errors remain, the entire project is redone, as many times as it takes to achieve harmony between all the data. Excellent synthetic seismograms, wavelet extractions, and inversions follow.

Shear Sonics (for AVO)

A special case of Log Reconstruction is the calculation of Shear Sonics (Dipole Sonics) from other curves. These logs are necessary for AVO, elastic inversion, and similar processes involving shear waves, but they have been recorded in very, very few wells. Fortunately, a simple set of relationships allows computation of shear velocity from the Reconstructed logs.

Given a calibration set of 6 wells in the Gulf of Mexico, we calculated a shear sonic for a well in Indonesia: the client judged it superior to their recorded log. This offers you a way to save money on well logging.

Pressure Prediction from Seismic Stacking Velocities

Beware of using stacking velocities to predict pressure, if you are calibrating to a well with incorrect pressure information!

In existing wells, the pressure is approximately known from mud weight data, plus various pressure test tools. However, a much more accurate, detailed pressure curve is available from the Log Reconstruction process. Armed with this fully accurate pressure data, we can correctly deduce the relationship between velocity and pressure. Then stacking velocities can be used to predict pressure with unprecedented accuracy.

Many firms are using the pressure data to understand fluid migration regimes, trapping mechanisms, and the like.

Formation Evaluation

What-if Cases (Modeling)

Many types of modeling are available once the petrophysical relationships are known. The most common is Fluid Substitution, where the effects of various amounts and types of hydrocarbons in the reservoir are studied. Also popular is Lithologic Modeling, where the effects of different lithologic sequences are modeled.

Wavelet Extraction

Given properly corrected logs, we can use well-based wavelet extraction to find the best operator (in phase and frequency) to tie your synthetic seismogram to your seismic. If this is done at different points vertically within each well, and horizontally between wells, the result should be a stable wavelet field. At this point you are ready to get the full benefit from advanced seismic techniques, such as forward modeling, inversion, and AVO.