Field estimates of fracture compliances using active & passive seismics

A. F. Baird*, J. P. Verdon, J. M. Kendall, G. Foord, A. Stork, P. J. Usher

*Corresponding author for this work

Research output: Chapter in Book/Report/Conference proceedingConference Contribution (Conference Proceeding)

Abstract

Fracture networks provide a major control on the permeability of petroleum reservoirs, thus the ability to remotely characterize them is of great importance. Seismic anisotropy is a useful attribute to determine fracture orientation and provide some indication of the fracture density, however it is often difficult to constrain their ability to facilitate fluid flow. A potentially useful property to provide insight into this is the ratio of the normal to tangential fracture compliance (ZN/ZT). ZN/ZT is sensitive to many properties including: The stiffness of the infilling fluid, fracture connectivity and permeability, and the internal architecture of the fracture. Although P-wave anisotropy is primarily controlled by ZN and S-wave anisotropy by ZT, we find that for waves propagating oblique to the fracture plane, both P- And Svelocities are sensitive to the ZN/ZT ratio. Thus we can exploit these sensitivities to can gain some insight into ZN/ZT of subsurface fractures. We demonstrate this by estimating ZN/ZT using: (a) Azimuthal variations in P- And S-velocities estimated from a near-surface refraction survey, and (b) shear wave splitting measurements from a hydraulic stimulation microseismic dataset. In both cases we found that the natural fracture ZN/ZT was relatively low (∼0.2-0.3), but in the case of the hydraulic stimulation ZN/ZT appeared to increase after the initial stage of the stimulation. We suggest this may be due to the increase in fracture connectivity and the generation of new clean fractures.

Original languageEnglish
Title of host publication5th EAGE Passive Seismic Workshop: From Wish List to To-Do List
PublisherEAGE Publishing BV
ISBN (Print)9789462820319
DOIs
Publication statusPublished - 1 Jan 2014
Event5th EAGE Passive Seismic Workshop: From Wish List to To-Do List - Lisbon, United Kingdom
Duration: 28 Sep 20141 Oct 2014

Conference

Conference5th EAGE Passive Seismic Workshop: From Wish List to To-Do List
CountryUnited Kingdom
CityLisbon
Period28/09/141/10/14

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