Mapping and time-lapse analysis of South Arne Chalk fault network using new developments in seismic dip computation

Abstract

In a reservoir, faults at the limit of the seismic resolution can be crucial to explain production history and to optimize field development. However, in most cases the detail required to describe such subtle features depends on the assistance of seismic attributes and semi-automated interpretation techniques. We generated a detailed description of the fault network in the South Arne Chalk Group using a workflow based on a globally consistent computation of the seismic dip. This led to more accurate seismic edge attributes than gained with standard dip estimation techniques. We analysed each fault set and qualitatively assessed its control on fluid flow. Our investigation suggests that the two fracture sets that influence production developed along the same WNW-ESE structural trend and cannot be separated based on the seismic data alone. These faults were active both during and post Chalk deposition. We observe ENE -WSW lineaments that match the pattern of a time-lapse seismic amplitude anomaly associated with water injection. It remains to be verified whether these lineaments could be an extension of overburden faults, as well as whether the increased intensity of the fault network as seen on the 2005 v. the 1995 3D seismic survey was caused by production effects.

A naturally fractured chalk reservoir in the Ekofisk Formation: characteristics, petrography and stable isotope signature of cemented fractures and faults (The Kraka Field, Danish North Sea)

“…The anticlinal structure has been induced through halokinesis and has undergone several development phases caused by the movements of an underlying Permian salt dome initiated during the Triassic and extending to the Early Neogene (Rank-Friend & Elders, 2004;Rasmussen et al, 2005). During late Miocene to present, the Danish Central Graben experienced a high rate of subsidence and further deformation and possible fracturing of chalk reservoirs are thought to have occurred in this time interval (Jensenius, 1987;Astratti et al, 2015). The deformation phases have resulted in the reservoir being naturally fractured with large open fractures, both shear and extensional, which act as the main permeability enhancers (Jørgensen & Andersen, 1991).…”

Fundamental controls on fluid flow in carbonates: current workflows to emerging technologies

“…Some studies have focused on methods to detect fracture corridors (Arasu et al 2010). Astratti et al (2014) develop this theme, arguing that most seismic attributes only highlight subsets of a desired solution. Their 'seismic triple combo' workflow combined three individual attributes (amplitude, structural and uncertainty attributes) into one aggregate fault attribute.…”

“…In this volume, Astratti et al (2014) introduce time-lapse seismic data as a means to capture information on the connectivity of fracture networks on production timescales in chalk reservoirs. Integration of the production history with the comparisons of repeated surveys was used to link changes in fault images to qualitative interpretations of changes in faultflow behaviour (e.g.…”