Advanced analysis of marine seismic data

Offentlig prosjektsammendrag

Regarding seismic inversion development: Marine site characterization projects that investigate ground conditions and geohazards within the so-called overburden are usually limited by basic interpretation techniques. No quantitative information is regularly derived from geophysical data beyond qualitative inferences of sediment characteristics based on seismic facies architecture. The purpose of this project is to investigate advanced seismic interpretation techniques from hydrocarbon prospecting, like seismic inversion, and to make parts of them applicable for marine site characterization projects, within oil and gas development, but also for foundation of offshore wind-farms and fish-farms. Regarding AVO development: Traditionally in the marine site survey industry, shallow gas interpretation has relied upon relative amplitude contrasts (the presence of anomalous ‘bright-spots’), along with other visual indications which infer the presence of gas. These visual assessments are generally useful, however do contain limitations. We might encounter false-positives and/or false-negatives which might unintentionally exclude genuine anomalies, or consider innocuous events to represent gas. These limitations provide the motivation to explore additional methods of shallow gas analysis, with the aim of adopting a more quantifiable approach, and extracting maximum value from the datasett. The challenge is to achieve these objectives whilst maintaining an efficient workflow which could be applied to future projects. Here, we develop one approach to meeting these goals, by using AVO "Amplitude Verses Offset" analysis of the data. In essence, AVO models different types of seismic wave as they pass through the reflective medium, and by comparing reflective amplitude in near receivers compared to far receivers, we can use these differences to infer that the reflective medium is a normal geological contact, or a trap of shallow gas.