Victor Aarre

Globally consistent dip estimation

The primary objective of surface seismic is to provide an image of the layers of the interior of the earth. The seismic experiment will in particular highlight the position of the interface between layers of rocks of different types within the earth. In order to map/interpret particular interfaces laterally, we need to be able to track the change in vertical position of those interfaces. The change in vertical position, from one spatial location to a neighboring location, is referred to as the dip of the layer in the direction towards that neighbor. This paper presents a novel algorithm for the estimation of dips which employs several global dip consistency constraints. This new algorithm also highlights areas where globally consistent dips are difficult to obtain.

Volumetric impact of fault perturbation in the first Fresnel zone

AbstractResolution within seismic imaging must be understood in all three dimensions to make quantitative approximations of subsurface geometries. Constructive interference of incident spherical waves within the first Fresnel zone will limit the resolution due to spatial aliasing. Motivated by the problem of estimating the influence of this effect on the volume uncertainty several interpretations of trapping faults, being equally probable within the first Fresnel zone, are perturbed and multiple realizations of a structural model constructed. After estimating the depth dependent mean frequency and velocity within a zone around the fault plane, the fault interpretations are stochastically perturbed. The frequency- and velocity-dependent perturbations of the dips are analytically derived based on geometric considerations. The anticipated maxima of the repositioned fault dips specify thresholds for deterministic definitions of high and low cases for the fault geometries in a framework. The structural models,...

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.

Improved Fault/Fracture Mapping through the Application of a Novel Dip estimation method

The objective is to assist seismic interpreters to efficiently map complex faulted areas with good details, for future fault and fracture modelling purposes. Accurate seismic dips are very important in this context, primarily because dips are the mandatory input to the curvature attribute, which is a generally accepted fault/fracture indicator. Therefore, accurate dip estimation becomes extremely important if we want to apply automated techniques for fault extraction. We will here present preliminary results of the application of a novel algorithm for the estimation of dips, which employs a set of global dip consistency constraints. The examples are from a carbonate reservoir in the Danish part of the North Sea.

A Dual Representation of Multiscale Fracture Network Modeling - Application to a Giant Carbonate Field, UAE

This paper describes a novel workflow applied on a Middle East case study, aiming to detect and characterize fracture corridors in a Type III carbonate reservoir (Nelson, 2001). Fracture corridors are zones of fracture clustering dominated by highly persistent parallel joints thought to promote fluids arrival. The innovative aspects introduced in the study include the detailed 3D seismic analysis to detect the location of the fracture corridors, supported by new developments in dip calculation and seismic fault detection techniques (Aarre, 2010), and the introduction of a hybrid model to characterize and model the fracture network (Souche et al., 2009). This novel dual technique combines traditional Discrete Fracture Modeling (DFN) to model large fractures and a new statistical approach dealing with smaller scale fractures. It allows a more quantitative approach to fracture characterization than the current standard methods, enabling the computation of more rigorous statistics and the calibration of intermediate and final results.