Schlumberger

Well-Driven Seismic Borehole Information and Surface Seismic Integration Workflow

Integrating well data throughout the seismic workflow for superior imaging and inversion

Well-Driven Seismic borehole information and surface seismic integration workflow incorporates borehole information throughout the surface seismic workflow to provide better seismic images, more reliable stratigraphic interpretation, and greater confidence in seismic reservoir characterization.

Wireline logs (compressional, shear, and density), vertical seismic profiles (VSPs), and surface seismic data represent the elastic response of the earth at various scales of resolution. A principle of the Well-Driven Seismic workflow is that these data should be processed with respect to their mutual consistency, i.e., the seismic data must tie with logs and VSPs in time and depth. Incorporating all available borehole information makes it possible to optimize the entire seismic workflow to deliver seismic images of superior resolution (in time or depth) and calibrated prestack seismic amplitudes that are suitable for inversion and detailed seismic reservoir description.

Earth properties from logs, VSPs, and surface seismic data

The Well-Driven Seismic workflow combines new proprietary software and analysis techniques from WesternGeco and Schlumberger to derive an earth property model from the integrated analysis of wireline logs, VSPs, and surface seismic data. The property model includes compressional and shear velocities, attenuation (Q) factors, VTI anisotropy parameters, and interbed multiple mechanisms and is derived at the well location (or locations) and extended across the survey area in 3D. The 3D model is applied in the seismic processing sequence for true amplitude and phase recovery, deconvolution, multiple attenuation, anisotropic prestack time and depth imaging (including of converted-wave data), AVO analysis, and 4D processing.

Well data for high-resolution seismic imaging

Well information can improve many key stages of the conventional seismic processing sequence. VSP data provide excellent discrimination of primary and multiple events for guiding surface seismic multiple attenuation processes. Furthermore, interbed multiple mechanisms identified in separated VSP wavefields are used as input to data-driven multiple attenuation processes, such as interbed multiple prediction (IMP). Inverse-Q operators derived from VSP data (and new methods for walkaway VSP data) can significantly improve seismic resolution. We employ a proprietary deconvolution process that is constrained by the level of the signal-to-noise ratio in the seismic data and by the well reflectivity to further enhance the seismic resolution. The calibrated anisotropic velocity model is vital for prestack time and depth migration (including converted waves) to improve steep-dip imaging, lateral positioning of reflectors, signal-to-noise ratios, and seismic resolution.

Optimized well ties

The Well-Driven Seismic workflow optimizes the processing sequence and its processing parameters to tie the seismic data to the wells. Attributes based on the well tie and on the quality of the extracted wavelets are used for deterministic seismic processing decisions. Space-adaptive wavelet processing corrects 3D seismic data to true zero phase between well locations and stabilizes residual spatial wavelet variations.

Borehole-calibrated seismic inversion

Greater sensitivity to seismically derived reservoir attributes is provided through calibrated AVO or acoustic impedance inversion. The well data are particularly important for successful processing of seismic data for inversion. Compensation for the offset-dependent effects of Q, geometric spreading, transmission losses, and anisotropy is essential for processing data over very long offsets, where the strongest AVO expression of the reservoir may be visible. The workflow calibrates the AVO signatures in the prestack seismic data with the offset-dependent amplitude response synthesized from well logs or the response expressed in the walkaway VSP to provide assurance of the seismic processing sequence.

By optimizing the seismic processing sequence for resolution and consistency with the well data, the Well-Driven Seismic workflow is a vital prerequisite for acoustic impedance or AVO inversion and subsequent reservoir characterization.

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WesternGeco

Integrating Borehole Information for Improved Seismic Imaging

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