title: Emulation of petroleum well-logging D-T2 correlations on a standard benchtop spectrometer.
abstract: An experimental protocol is described that allows two-dimensional (2D) nuclear magnetic resonance (NMR) correlations of apparent diffusion coefficient D(app) and effective transverse relaxation time T(2,eff) to be acquired on a bench-top spectrometer using pulsed field gradients (PFG) in such a manner as to emulate D(app)-T(2,eff) correlations acquired using a well-logging tool with a fixed field gradient (FFG). This technique allows laboratory-scale NMR measurements of liquid-saturated cored rock to be compared directly to logging data obtained from the well by virtue of providing a comparable acquisition protocol and data format, and hence consistent data processing. This direct comparison supports the interpretation of the well-logging data, including a quantitative determination of the oil/brine saturation. The D-T(2) pulse sequence described here uses two spin echoes (2SE) with a variable echo time to encode for diffusion. The diffusion and relaxation contributions to the signal decay are then deconvolved using a 2D numerical inversion. This measurement allows shorter relaxation time components to be probed than in conventional diffusion measurements. A brief discussion of the numerical inversion algorithms available for inverting these non-rectangular data is included. The PFG-2SE sequence described is well suited to laboratory-scale studies of porous media and short T(2) samples in general.
authors.affiliation: Department of Chemical Engineering and Biotechnology, University of Cambridge, Pembroke Street, Cambridge CB2 3RA, United Kingdom.
authors.forename: J
authors.initials: J
authors.lastname: Mitchell
authors.forename: E J
authors.initials: EJ
authors.lastname: Fordham
mesh_terms: D000465:Algorithms; D004574:Electromagnetic Fields; D004578:Electron Spin Resonance Spectroscopy; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D010578:Petroleum / Q000032:analysis*; D016062:Porosity; D012987:Soil / Q000032:analysis
chemical_list: D010578:Petroleum; D012987:Soil