Applications of the coherency cube in the UKCS

Abstract

Seismic coherency is a measure of the similarity between seismic traces. Coherency data play an important role in the delineation of structural and stratigraphic features by enhancing the images seen on conventional 3D seismic data. Through integration of coherency data with other technologies and calibration to well data, new applications are emerging. This paper discusses three examples from the UKCS. Partial permeability barriers in the Leman Field were known to exist from well pressure data. A coherency cube revealed several lincations that separated the wells. These lineations can be correlated to a previously unmapped fault trend with very small throws on the vertical seismic lines. The coherency cube therefore provided additional information to improve confidence in the interpretation and enabled significant time-savings in the fault pattern interpretation. Coherency data were used to assist in the welt planning for the Arkwright Field development programme. Coherency slices through high pressure zones were characterized by polygonal faulting, whilst less faulting was observed in areas of lower pore pressure. These pressure zones were calibrated to pore pressures predicted from the original discovery well. The development trajectories were optimized with respect to the fault patterns interpreted from the coherency data. Model predictions were confirmed by drilling results. A coherency cube was utilized to enable a quick interpretation of the structural framework of an area of the Central Graben. In particular the distribution of faulted Triassic rafts and Jurassic rifts is easily observed because the relatively coherent Jurassic reflectors contrast well with the relatively incoherent Triassic seismic reflectivity. These three examples illustrate how coherency data can be used in production, development and exploration settings to improve the imaging of geological features ranging in scale from reservoir barriers to major faults.