Spectral decomposition: an aid in characterizing field architectures of the Laggan and Tormore fields, Faroe–Shetland Basin

Abstract

Spectral decomposition analyses seismic reflectivity data in the frequency domain, providing images of the subsurface that complement conventional seismic interpretation. It is a highly visual tool that allows additional value to be extracted from seismic data, to aid in the identification of geological information and to be used in conjunction with more traditional methods such as amplitude extraction and attribute analysis. The methods of spectral decomposition chosen utilized a top reservoir seismic reflection surface, with the selected dominant frequency volumes coloured and recombined in a spatial context to produce various red–green–blue (RGB) blends. Application of spectral decomposition to the Laggan and Tormore fields revealed the varied distribution of turbiditic sands, as well as extensive east–west faults that have previously been inferred from seismic reflection data. These enhanced images of the reservoir provide a more detailed interpretation of the field architecture and have been captured in DONG E&P UK Ltd's own fault and reservoir models, leading to a greater understanding of potential field development outcomes and future well placement decisions. Attempts to distinguish hydrocarbon effects using spectral decomposition proved difficult, although interesting frequency variations around a known gas–oil contact (GOC) were noted.

Slip sliding away: Enigma of large sandy blocks within a gas-bearing mass transport deposit, offshore northwestern Greenland

“…An extraction along the top reservoir horizon clearly depicts a dominant bright white frequency response over much of the reservoir area (Figure 5). This represents high saturations from all three blended frequencies and is a response typical for a relatively shallow (550 ms [550 m {1804 ft}] using an average velocity of 2.0 km/s [6562 ft/s]) below the seabed) gas sand reservoir (Wright et al, 2018). Other areas of the reservoir and surrounding decollement surface show dominance toward the low-frequency (red) response.…”

“…Spectral decomposition was completed and interpreted using Geoteric, which allowed for noise cancellation, seismic frequency selection, and color blend cube creation (Castagna and Sun, 2006). Surface extractions were then taken from color blend cubes for interpretation (Wright et al, 2018).…”

The Petroleum Geology of NW Europe: 50 years of learning – a platform for present value and future success. An overview

“…There is also evidence that ideas that have been developed and applied to new frontier basins, such as West Africa, the Gulf of Mexico and other areas, are being brought to bear to create future value in a number of the NW European basins and fields. The value of seismic is clear in many of the papers (Porcupine, Watremez et al 2016;Rosebank, Poppitt et al 2016;andHuntington, Edwards et al 2017 andWright et al 2017 are good examples). Challenging historical paradigms and lateral thinking are also demonstrated by many papers, including Belaidi et al (2016) (Lancaster), Goffey et al (2016) (Bror Tuck and Lille John) and Catto et al (2017) (Cygnus).…”