Q-compensated reverse-time migration for natural gas hydrate using fractional viscoacoustic wave equation

Abstract

Natural gas hydrate (NGH) is a potential clean alternative energy source for fossil fuels. In seismic imaging profiles, NGH is often identified by the bottom-simulating reflection (BSR), which is characterized by strong reflection amplitude and negative polarity. High-resolution and amplitude-preserved seismic imaging are demanded for the detection of NGH. However, the traditional acoustic reverse-time migration ignores the attenuation characteristics of the medium, which leads to reduced amplitude and distorted phase of the seismic wave. In particular, when the hydrate saturation is low or the underlying formation does not contain free gas, it is difficult to observe the identifiable BSR in the traditional acoustic imaging profile, which causes difficulties in the identification of NGH. Here, we introduce the fractional viscoacoustic wave equation to perform the Q-compensated reverse-time migration (Q-RTM) for NGH, which can accurately recover the amplitude loss, correct the phase distortion, and provide high-resolution and high-illumination imaging results. Finally, Q-RTM can effectively enhance the BSR, reduce the uncertainty of hydrate identification, help to confirm the location and spatial distribution of the gas hydrate-bearing sediments, further refine the geological properties, and provide some theoretical basis for the exploitation and drilling of hydrate.

Keywords

• Natural gas hydrate
• Complex structure imaging
• Fractional Laplacian
• Q-Compensation for attenuation