VSP Processing

Accurate monitoring of reservoir changes caused by injection and production

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Measure velocity changes and build better velocity models with borehole surveys using 3D VSP technology

Many subsurface imaging problems cannot be solved without a 3D survey, and when a survey also needs to be performed in the borehole, the solution is 3D vertical seismic profile (VSP) technology.

With increased computer power,3D finite difference modeling is now practical for survey evaluation and design of 3D VSPs. In complex geological environments, better model-building methods and more accurate imaging algorithms, such as reverse-time migration (RTM), are critical for successful 3D VSP surveys.

Improve model calibration

For 3D VSPs, depth migration of individual receivers can be carried out to generate common image point (CIP) gathers. The automated process allows picking reflection events on these gathers for detailed, accurate hybrid grid and layered velocity models in the most challenging environments.

3D views of a SAGD baseline 3D VSP survey (A), repeat survey (B), difference section (C), and a sweetness attribute (D) showing two observation wells and four horizontal injection and production pairs. Note higher resolution of VSPs than surface seismic (background) and changes in the reservoir (B, yellow) due to steam injection.

Example of three-component time picking.

Platform and hardware

Our VSP processing is conducted using Q-BorSeis borehole seismic processing, a fully integrated suite of applications in the Omega geophysical data processing platform. The unique aspects of VSP data and borehole seismic geometries are managed through tailored and proprietary algorithms.

Time picking

The manual QC and edit of picked times is facilitated by our fully interactive multiview capability within the Omega platform.

Data rotations

Prior to rotation, bad traces are removed, navigation is confirmed, and traveltimes are verified. Rotated data is output in SEG-Y format.

Multiview

View the data in a variety of domains, ranging from a map view of the entire dataset to common receiver and shot domains.

Single-component processing

Each individual trace is examined and trace headers verified for the entire data volume prior to velocity filter wavefield separation and deconvolution. Velocity filtering is performed on the vertical channel only. Coherent noise such as shear waves can be reduced using a variety of filtering techniques.

If the input data quality is good, processing will result in a clean, high-resolution compressional wavefield. In deviated wells, we use earth-frame true vertical data.

Three-component processing

Each trace is examined and trace headers verified for the entire data volume prior to data rotations. The x, y, and z axis traces are carried in the processing. Data rotations put the recorded x, y, and z data into an Earth reference frame, and appropriate wavefield separation would be applied to separate down- and upgoing P- and S-waves.

If data quality permits, then we apply Wavesip three-component wavefield separation based on parametric inversion to separate compressional and shear wavefields while simultaneously performing up and down separation. This is followed by deterministic deconvolution. Wavesip separation is applied if data quality permits and this is followed by deterministic deconvolution. PP and PS wavefields are processed independently.

Model building, tomography, and statics

Our integrated tools improve 3D model building, survey design, salt proximity analysis, and tomography. Gtomo is our 3D tomography tool and includes flexible options for constraining model updates based on smoothness or layer exclusion. If a 1D earth model is appropriate, then additional functionalities are available, including 3D NMO correction and AVA analysis.

3D migration

We provide

ray-based Kirchhoff and generalized random transform (GRT)
wave equation migration (WEM)
reverse time migration (RTM).

Final deliverables for the migration include a 3D P-wave data volume migrated in depth SEG-Y format. If three-component processing is undertaken, followed by 3D migration, then a 3D PP wavefield, 3D PS wavefield volume migrated in depth, or both can be output in SEG-Y format. The corresponding two-way time (TWT) volumes are delivered as well.