Jonathan Liu

Integrated velocity model estimation for improved positioning with anisotropic PSDM

There are many geologic settings where anisotropic migration is necessary to obtain accurate seismic images. While this is well known, stable anisotropic parameter estimation has posed a serious challenge. Seismic data, though extensive in coverage, cannot constrain the anisotropy parameters alone (Tsvankin and Thomsen, 1995). The set of parameters is better constrained by integrating the seismic information with certain types of well data. However, the well data are generally sparse, so the parameters are only constrained at a few locations. Nonuniqueness is obviously a fundamental issue in our estimation problem.

Amplitude and Bandwidth Recovery Beneath Gas Zones Using Kirchhoff Prestack Depth Q-Migration

Summary When imaging geologic structures below a viscoaoustic overburden, it is important to account for amplitude dimming, frequency loss, and phase distortion. Several viscoaoustic wave-equation based methods have been developed to solve this problem. We present a Kirchhoff approach. The technical significance of this approach is that we have found an efficient way to compute frequency-dependent traveltimes, which are crucial in the Kirchhoff integral. The validity of our technology is illustrated by data examples.

A robust and accurate seismic attenuation tomography algorithm

Summary We developed a seismic-attenuation-tomography algorithm for improving image amplitude fidelity and other geophysical applications. This algorithm is based upon the centroid-frequency-shift method. However, compared with the conventional centroid-frequency-shift method, our algorithm has been significantly improved through the

Integrated Velocity Model Estimation For Accurate Imaging

Surface seismic reflections, surface seismic direct arrivals, well data and prior geologic information can be used to constrain a subsurface velocity model.

Noise suppression by beam migration with local dip filtering

We have developed a technique that incorporates local dip filtering into beam migration in order to remove coherent noise by differentiating the reflection dip angles of signal from noise. With the estimated upper and lower bounds of the reflection dip angles of the signal (or noise) in a target zone, the method is able to remove the noise (or signal) out of these bounds, so that only signal (or noise) within the bounds is preserved in the target zone. The migrated section, with local dip filtering in the target zone, is subsequently merged with the whole migration section with proper tapers.

Pre‐stack anisotropic depth imaging of Forseti (North Sea) 2D 4C data

Tomographic inversion has been applied to derive anisotropic velocity models for the 2D 4C Forseti data. Application of these models in anisotropic pre-stack converted-wave depth imaging produces improved consistency between positive and negative offsets for PS images in both the pre-stack and stack domains. It also significantly improves image quality over that obtained by traditional prestack time migration methods. Inclusion of small anisotropy parameters that have little impact on PP imaging is helpful for improved PS imaging. Also, the correlation between the PP and PS depth images is much better than between the prestack time migration analogs.

Integrated velocity model estimation for accurate imaging

Surface seismic reflections, surface seismic direct arrivals, well data and prior geologic information can be used to constrain a subsurface velocity model. These various sources of subsurface velocity information have different strengths and weaknesses. Integrating all available velocity information into a velocity model increases the accuracy of the model by offsetting the weakness of one data type with the strengths of another. We call the process of building a model that integrates all data integrated velocity model estimation.