Mega-merge processing with attenuation compensation from 3D pre-stack seismic data: A case study from A loess plateau area, southwest of Ordos Basin, China

Abstract

The Ordos Basin, known as ‘China's Golden Triangle of Energy’, is the second-largest sedimentary basin in China and is abundant in oil and gas resources. Due to the presence of a thick loess and the high costs associated with high-density data acquisition, merging existing 3D seismic data is the most efficient approach for exploring its expansive areas. The current research focus on the largest 3D merged seismic data set, covering 3100 km² in the southwestern part of the Ordos Basin. This area was divided into three blocks, each processed independently at different periods and merged using post-stack merge processing. However, a significant issue with this approach is the discrepancy in the closure observed at the boundaries of seismic profiles, which reduces the reliability of imaging complex structures near the edges. To address this issue, our study proposes a mega-merge processing (MMP) for the Ordos Basin. This MMP aims to resolve the imaging inaccuracies around profile edges and deliver high-quality, consistent pre-stack 3D imaging results, facilitating subsequent tectonic interpretations and reservoir predictions. The MMP methodology comprises four key technologies: (a) first arrival tomographic inversion constrained by micro-logging for static correction; (b) a novel pre-stack fidelity denoising technology according to different noise types for abnormal energy interference and other noise; (c) a broadband consistency processing flow, incorporating wavelet consistency with sonic logs, amplitude consistency, and broadband processing, enhanced by near-surface Q-compensation and a surface-consistent deconvolution technique; and (d) effective Q-value modelling and the pre-stack time migration (PSTM) is adapted in the OVT domain. The effectiveness of our MMP approach is validated using large-scale 3D seismic data from a loess plateau area in the southwest Ordos Basin. The results demonstrate that the MMP successfully eliminates time and energy discrepancies present in the original seismic data, which were due to varying acquisition parameter influenced by differences in source and receiver conditions. Additionally, it resolves issues related to uneven spatial sampling, refines Q-field modelling precision, and reduces matching errors between seismic and sonic logs, thereby enhancing the resolution and accuracy of seismic imaging. Consequently, this improvement facilitates a more precise delineation of fault system and deepens the understanding of the paleo-topographic characteristics of the Chang 7 in the Mesozoic era.