Fracture detection using 3D seismic data: A physical modeling study

Abstract

A seismic physical experiment has been conducted to acquire wide-azimuth P-wave 3D seismic data with a scaled down model (1:10000) and scaled-up frequencies (10000:1). Our aim is to verify the physical basis of using P-wave attributes for fracture detection and to understand the usage of these attributes and their merits. The model consists of a fractured layer (artificial limestone) sandwiched between two isotropic layers (Epoxylite). Inside the fractured layer there is a dome and a fault block for investigating the effects of structural variations. About 20 km 2 of wide-azimuth 3D data was acquired with a Pwave source. The physical modeling confirms that the Pwave attributes (traveltime, amplitude and velocity) exhibit azimuthal variations diagnostic of fracture-induced anisotropy. Two processing techniques are used to extract the fracture information: full-azimuth surface fitting and narrow-azimuth stacking. The results show that the commonly used narrow-azimuth stacking technique may enhance the acquisition footprint. The final fracture orientation and intensity maps estimated using the surfacefitting method agree with the physical model parameters.

Azimuthal AVO over a simulated fractured medium: A physical modeling experiment

“…An alternative to numerical modeling methods, physical modeling has been attempted by many researchers on the topic of AVAZ in recent years. 3D physically-modeled seismic data have been acquired on simulated fractured media to detect fracture zone, fracture orientation, and density; Tadeppali (1995); Luo and Evan (2001); Wang and Li (2003). They used material composed of epoxy-bounded fiber sheets or laminate phenolic material to simulate the fractured media.…”

Estimation of density and fracture orientation in HTI media through azimuthal analysis of P-waves

“…Lefeuvre (1994) showed a methodology to detect fractures by studying the variation in amplitudes of the P wave based on offset and azimuth. Physical modeling (Wang & Li, 2003;Sayers & Ebrom, 1997) shows that for moderately far offsets (25° to 35° angle of incidence), P waves that travel on the plane parallel to vertical fractures have greater velocity than P waves traveling on a plane perpendicular to fractures. Azimuthal analysis of amplitude with offset of acoustic wave can be used to predict fractures (Li, 1999).…”

“…Simulations have been performed to study the effect of fractures on acoustic wave velocity (Wang & Li, 2003;Luo & Evans, 2004) and there has been interest in the use of azimuthal variations of seismic amplitude to detect high productivity points related to fractures (Hao et al, 2011). Traditionally, information about fractures has been available in outcrops, cores, well logs or in the Fullbore Formation Microimager FMI.…”