--> --> Abstract: Imaging Pore Connectivivity Through Sealing Fault Rocks with NMR, by Mike Mallett, M. Ben Clennell, John H. Strange, and Quentin J. Fisher; #90914(2000)

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Mike Mallett1, M. Ben Clennell2, John H. Strange1, Quentin J. Fisher3
(1) University of Kent, Canterbury, United Kingdom
(2) Universidade Federal da Bahia, CPGG-IEGO, Salvador, Brazil
(3) University of Leeds, Leeds, United Kingdom

Abstract: Imaging pore connectivivity through sealing fault rocks with NMR

Detailed knowledge of fault rock properties is necessary for predicting hydrocarbon column heights and for modelling pressures and flow rates, flow pathways and sweep efficiencies. Pore size distribution and connectivity are the critical controls on the permeability and capillary barrier performance. The NMR group at the University of Kent has developed a novel technique for measuring pore size distributions, known as NMR cryoporometry, that has previously been successfully applied to concrete. Initially, the method produced a sample-average pore size distribution. Now application of magnetic resonance imaging in association with cryoporometry can produce 3D information about the porous structure of the sample. As the temperature of a frozen sample is raised incrementally, the liquid in smaller pores and throats melts first, and becomes visible in the NMR volume image, highlighting the critical pathways for percolating flow. The size of the pores visible at any temperature is calculated from the Gibbs-Thomson equation. Here we present 3-D core images and 2-D slices for a suite of samples from North Sea oil and gas fields, and outcrop analogues. These are discussed in the light of permeability, mercury injection porosity, and electron microscope image data collected on the same cores by the Rock Deformation Research Group at the University Leeds. The study highlights the need for detailed core analysis and truthing with images, and adds a new dimension to interpreting the results of capillary percolation measurements such as mercury injection tests. Developments involving multiphase flow tests, addressing wetting issues will be discussed.

AAPG Search and Discovery Article #90914©2000 AAPG Annual Convention, New Orleans, Louisiana