Simulation of Transient Well-Test Signatures for Geologically Realistic Faults in Sandstone Reservoirs

Stephan K. Matthäi*, Atilla Aydin, David D. Pollard, Stephen G. Roberts

*Corresponding author for this work

    Research output: Contribution to journalArticlepeer-review

    23 Citations (Scopus)

    Abstract

    For the design of production strategies one must identify how faults that are detected in seismic surveys influence fluid flow in hydrocarbon reservoirs. In this study we use the Entrada sandstone formation. Arches Natl. Park, Utah, as an outcrop analog of a faulted sandstone reservoir. Field measurements of the geometry, thickness, and layered permeability of the normal faults that cross-cut this sandstone are incorporated in two-dimensional (2D) fluid-flow models, facilitating the simulation of fault signatures in transient well tests with a high-resolution finite-element method. In our simulations, structure and inhomogeneous permeability lead to fault signatures in derivative plots that differ significantly from those of idealized impermeable barriers. Highly permeable slip planes facing the well create the illusion of a nonsealing or nonexisting fault because remote fluids are focused along the slip planes toward the well. Measured low, fault-normal permeability shields fault-bounded blocks of the analog sandstone reservoir from drawdown and large pressure differentials build up across faults during production. Thus, test data from a single well are insufficient to assess the flow properties of a nearby fault with an inhomogeneous permeability like the normal faults in the Arches Natl. Park. Test responses from multiple wells need to be considered to detect fault segmentation or fault terminations even if the general fault trend is underpinned by seismic data. Flow paths in the reservoir during production are complex. Importantly, formation water is likely to flow into the reservoir along the permeable slip planes of the normal faults.

    Original languageEnglish
    Pages (from-to)62-76
    Number of pages15
    JournalSPE Journal
    Volume3
    Issue number1
    DOIs
    Publication statusPublished - 1 Mar 1998

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