Time-lapse analysis on repeated well logs: A focus on shales

A. Jaramillo, M. D. Mangriotis, C. MacBeth

Research output: Contribution to conferencePaperpeer-review


Shales play a significant role controlling fluid flow and seismic-wave propagation due to their low permeability and anisotropic structure. Field observations indicate that during production, pore pressure reduction in the reservoir generates strain deformation in the overburden that varies with lithology and stress path. 4D seismic is a primary source of spatial information on these geomechanical effects. For this purpose, a physical model that links the velocity perturbations to the vertical strain via a factor R is widely used. This study aims at computing R factors from a repeated well log analysis. The combination of seismic with petrophysics is key to understand the physics of the lithology-dependent R. We performed the analysis on two Jurassic shales from Central North Sea to calculate R factors in the overburden shales based on the existing pore-related model proposed by Hatchell and Bourne (2005). The petrophysical analysis of repeated wireline logs has shown that R-factors of around 5 are appropriate for both the Heather and Kimmeridge clay based on an HBR model using log-derived time-lapse porosity values. This range is in agreement with most published overburden R-values from seismic data, and can be explained by porosity deformation.
Original languageEnglish
Publication statusPublished - 28 Apr 2019


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