The effect of intra-reservoir and non-reservoir shales on 4D seismic signatures

Yesser HajNasser, Colin MacBeth

    Research output: Contribution to conferencePaper

    Abstract

    Shales are often regarded as inactive barriers in the reservoir simulation model and the surrounding rocks. Whilst this appears the correct approach for fluid flow modeling purposes, it is inaccurate for the pressure component of this process. In most clastic reservoirs experiencing pressure depletion, the sands naturally compact. This leads to the well documented extension of the non-reservoir rocks, but also the extension of the intra-reservoir shales. Less well known is that the shales have a finite, but small, permeability and pressure equilibration will occur with the reservoir sands. This diffusion process opposes the geomechanical effects. Numerical computation for a range of shale permeabilities suggests that intrareservoir shales of 1m to 10m thickness should be considered as active when quantitatively assessing the 4D seismic signature. Also it is observed that pressure depletion in the reservoir can `propagate' distances of as much as 50m into the shale over/under burden during the production time scale. The integration of these coupled mechanisms into forward modelling of time lapse seismic shows vertical time shift profiles different from those proposed for geomechanics alone.
    Original languageEnglish
    Pages4128-4133
    Number of pages6
    DOIs
    Publication statusPublished - Sep 2011
    Event81st Annual International SEG Meeting - San Antonio, United States
    Duration: 18 Sep 201123 Sep 2011

    Conference

    Conference81st Annual International SEG Meeting
    CountryUnited States
    CitySan Antonio
    Period18/09/1123/09/11

    ASJC Scopus subject areas

    • Geophysics

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  • Cite this

    HajNasser, Y., & MacBeth, C. (2011). The effect of intra-reservoir and non-reservoir shales on 4D seismic signatures. 4128-4133. Paper presented at 81st Annual International SEG Meeting, San Antonio, United States. https://doi.org/10.1190/1.3628068