Developments in the Magpore Method for Characterising Pore Fabrics and Permeability Anisotropy in Clastic and Fracture Reservoirs

<jats:p>This reference is for an abstract only. A full paper was not submitted for this conference.</jats:p> <jats:p>The magpore method determines the pore fabric of sediment samples by saturating the pore network with a magnetic fluid, then using anisotropy of magnetic susceptibility (AMS) measurements to define the preferred orientations of pore long and short axes. The full 3-D permeability anisotropy of the sample can be predicted from the results, particularly the anisotropy degree and directions of maximum and minimum permeability. The reliability of the method has been confirmed by comparing magpore data with directly-measured 3-D permeability anisotropy on sets of test samples. Examples will be shown that illustrate applications of the method to determining matrix porosity anisotropy in a range of different hydrocarbon reservoir facies. Results demonstrate that, in addition to the well-documented difference between vertical (KV) and horizontal (KH) permeability, many formations also exhibit azimuthal permeability anisotropy (ie variations in KH) of 10 to 20% or more, which is large enough to exert a significant influence on the fluid-flow properties of the reservoir. A particular attribute of the magpore method is that 3-D pore fabric measurements can be made directly on individual samples ranging in size from a few mm to several cm and on groups of samples spanning several metres or more. Thus, the method can provide permeability anisotropy data on spatial scales ranging from individual thin beds to metre-scale sand bodies. Applications of magpore for characterising microfracture fabrics in fracture reservoirs will also be illustrated. Laboratory loading experiments monitored by magpore measurements demonstrate that penetrative microfracture fabrics may develop at applied stresses well below the catastrophic failure stress of the rock (at which visible mesofractures appear). These microfracture networks can be characterised by the magpore method and potentially make a significant contribution to the porosity and permeability properties of these reservoirs.</jats:p>