Basic NMR Physics and MRIL® Tool Physics Outline Nuclear Magnetism Origin of the NMR signal Spin echoes and the CPMG pulse technique Relaxation times: T1 and T2 Commercial probe designs and investigation characteristics Experiment timing, nomenclature, and basic data flow MRIL - Principles and Applications 9/18/2018

Pulsed NMR Log Measurement Principle ... the basic NMR “experiment” ... N 1. Permanent magnet in tool polarizes hydrogen nuclei signal 2. Transmit train of RF pulses and records returning spin echo signals time This cartoon illustrates the basic NMR log measurement principle. Essential components of the basic NMR sensor or “probe” are 1) permanent magnet and 2) rf antenna Permanent magnet polarizes hydrogen. rf pulses from antenna used to manipulate magnetization so it can be measured. Can think of single NMR experiment consists of four steps 1. Build up hydrogen nuclear M in response to Bo. Note that build up is not instantaneous but takes finite amount time. Time constant for build up is called T1 and has an important influence on logging speed. 2. Transmit series of rf pulses. 1st pulse is unique; reorients M. Subsequent pulses are identical and generate spin-echo signals that are recorded by tool. 3. While tool is pulsing, peak amplitudes of spin echo signals received in antenna are recorded. 4. Finally, have to wait for magnetization to build back up again before starting next measurement. Echo amplitudes processed for two key pieces of information. Maximum signal ampl at zero decay time -> HI -> NMR porosity relaxation time distribution -> pore size, fluid prop’s -> flow prop’s S RF pulses 3. Wait for recovery hydrogen magnetization maximum signal amplitude µ fluid-filled porosity signal decay time µ pore size, fluid prop’s, flow prop’s MRIL - Principles and Applications 9/18/2018

MRIL - Principles and Applications The Resonance Effect z Excite transitions between spin states by irradiating at Larmor frequency: Bo z M y x z at equilibrium y x 90x° pulse now have eqm magnetization but how do we measure? done with secondary magnetic field set up by rf pulse two key requirements for resonance expt 1. B1 orthogonal to magnetization 2. frequency of ocillation = Larmor frequency B1 is an oscillating field generated by applying ac current to coil - can view B1 as exerting torque on M; causes M to rotate - modern NMR devices use rf pulses - most pulse NMR expt’s use 90 and 180 deg pulses Adsorption of resonant freq energy produces orient change in lab ref frame, M undergoes complex, spiral motion called precession: rotation about z and x - rotation freq about x determined by magnitude of B1 << Bo in ref frame rotating at Larmor freq, see simple rotation about x - rotation angle depends on duration of pulse - rotation freq about z = Larmor freq ~ Bo - 90 deg pulse shown here after pulse is turned of M precess about z, inducing signal (FID) in coil y B1 x rf pulse generates magnetic field B1 B1 oriented normal to Bo B1 oscillates at Larmor frequency precession in xy plane induces FID signal in coil MRIL - Principles and Applications 9/18/2018

MRIL - Principles and Applications T1 Polarization T 1A 1 1B 1S = + Relaxation Mechanisms for T1 Bulk Relaxation - intrensic property of fluid T1B = f (temperature, little pressure effect (liquids)) Surface Relaxation - Fluid-Rock interface T1S = f (S/V ratio (pore size) , relaxivity ) MRIL - Principles and Applications 9/18/2018

often estimated as a multiple of T1 Polarization 1.00 0.95 Polarized @ 95% often estimated as a multiple of 3 X T1 M(t)/Mo 0 1 2 3 4 5 sec. Polarization Time / T1 MRIL - Principles and Applications 9/18/2018

MRIL - Principles and Applications T1 and T2 B0 ML RF MT T1 characterizes the rate at which longitudinal magnetization builds up T2 characterizes the rate at which transverse magnetization decays MRIL - Principles and Applications 9/18/2018

MRIL - Principles and Applications A Single Spin Echo 90° 180° RF field time signal amplitude free-induction decay (FID) signal spin-echo signal time t 2t adapted, with permission, from Akkurt, 1990. MRIL - Principles and Applications 9/18/2018

Carr-Purcell Gradient Field Relaxation Rate  TE D = Intrinsic Relaxation Rate (sec) = Static Magnetic Field Gradient (gauss/cm) = Gyromagnetic Ratio (0.678 radians/gauss) = Pulse Echo Spacing, 2 (sec) = Diffusion Coefficient (cm2/sec) MRIL - Principles and Applications 9/18/2018

Idealized CPMG Spin-Echo Train envelope of spin-echo amplitudes µ TE Importance of TE in general, want as many echoes and as short a TE as possible more echoes => higher snr more echoes at early times => capture fast components more echoes at late times => resolve slow component (e.g. vugs) making TE short also reduces diffusion-induced rlxn .......... for typ grad’s, diffusion fx effectively eliminated with TE < ~1 msec limitation on echo spacing is mainly instrumental one Rick C talk on hardware will explain the problem and remedies time, t 2t 4t 6t 8t 90º pulse 180º pulse 180º pulse 180º pulse 180º pulse Shortening inter-echo spacing (TE) ... reduces diffusion-induced shortening of T2 improves resolution of short T2 components Increasing number of echoes ... increases signal-to-noise (SNR) improves resolution of long T2 components MRIL - Principles and Applications 9/18/2018

MRIL - Principles and Applications Data Acquisition ... 1. Record CPMG trains in phase-alternate pairs (PAPs) 2. Stack adjacent echo trains to improve signal-to-noise (SNR) + running average - ..... Basic data flow ... 1. record CPMG trains in phase-alt pairs at each depth 2. use standard method of stacking adjacent echo trains to improve signal-to-noise. snr improved bya factor = sqrt(#stacks) alternate phase of first (p/2) pulse corrects for baseline offset, drift reduces interference from ringing one tool also alternates frequency MRIL - Principles and Applications 9/18/2018

Relaxation Times: T1 , T2 , and T2* Pulse has two effects: 1. Increases thermal energy (spin temperature) 2. Introduces phase coherence at equilibrium 90° pulse After pulse is switched off ... rapid loss of phase coher- ence, time constant = T2* decay of transverse magnetization, time constant = T2 recovery of longitudinal magnetization, time constant = T1 pulse has two effects 1. impose increase spin temperature 2. impose phase coherence after 90 deg pulse, get rapidly decaying signal called FID immed after pulse, phases of spins have common phase after pulse is switched off, three things happen 1. spins rapidly loose phase coherence => T2* - dephasing due to spatial variations in Bo 2. decay of component of magntzn in xy plane => T2 3. recovery of component of magntzn along z: => T1 T1 and T2 due to underlying molecular processes - diffusion and fluid-solid interaction on pore surface can’t measure true relaxation with just 90 deg pulse - spins have just dephased but magntzn remains to measure T1 also must tip long mag into transverse plane - recall, can’t detect mag that has no component in xy plane T2 of primary interest for logging, can be meas faster than T1 T2 can be measured faster and thus is more practical for logging applications than T1 MRIL - Principles and Applications 9/18/2018

MRIL - Principles and Applications NMR Experiment Timing Mo T1 = 400 msec M || to Bo (longitudinal component) TW Mo T2 = 250 msec M ^ to Bo (transverse component) TE TX B1 RF field 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 time, seconds adapted from Murphy, D.P., World Oil, April 1995 MRIL - Principles and Applications 9/18/2018

MRIL - Principles and Applications Data Acquisition Tw time Tw = wait time Te = interecho time Ne = Number of echoes RA = running average time Te MRIL - Principles and Applications 9/18/2018

Effects of Pore Fluids on T1 Solids Fluids clay matrix capillary bound water BVI clay bound water movable water rock matrix hydrocarbons Invisible to NMR Variability in T1 due to Fluid Types Clay Bound Water Capillary Bound Movable Water Polarization (ideal) Hydrocarbons Time in sec. 0.3 1 3 10 MRIL - Principles and Applications 9/18/2018

Effects of Chemistry and Texture on T1 and T2 (water filled) Low Porosity Clean Cgr Sandstone T1 Build-up T2 decay Low Porosity Shaly Fgr Sandstone Higher Porosity Shaly Cgr Sandstone Time, sec. MRIL - Principles and Applications 9/18/2018

Rule of Thumb for T1 build-up 95 % Polarization Must use the correct Tw (wait time) to see full porosity MRIL - Principles and Applications 9/18/2018

Type of Measurements by MRIL® f: MRIL Porosity Effective porosity T2: Transverse Relaxation Time Differentiates capillary bound water from free fluids; important for permeability estimate. T1: Longitudinal Relaxation Time Identifies hydrocarbon fluids in the non-wetting phase. D: Fluid Diffusivity Differentiates between gas phase and liquid phase. D T1 MRIL - Principles and Applications 9/18/2018

Resonant Frequency F = g B0 Field Strength diminishes with increased distance from magnet. Proton “spin” rates are proportional to Magnetic Field Strength. F = g B0 For Hydrogen: g = 4258 Hz / Gauss F = Frequency (Hz) B0 = Field Strength (Gauss) Applying a radio frequency signal equal in frequency to the proton “spin” rate causes the protons to resonate. N S Magnetic Resonance occurs only where the rate of “spin” of the protons of hydrogen is equal to the frequency of an applied RF signal that is emitted from the tool. Hydrogen protons spin at a rate that is proportional to the strength of the magnetic field in which they reside. Since the MRIL tool contains a powerful permanent magnet, the magnetic field strength around the tool is a function of the distance from the magnet. Therefore, the rate of spin of hydrogen protons is proportional to the distance from the magnet. When the RF signal is emitted from the tool, magnet resonance occurs at a fixed distance around the tool. strength field distance MRIL - Principles and Applications 9/18/2018

MRIL Gradient Magnetic Field Sensitive Volume Formation Borehole Wall Magnet Antenna mud enables selective detection of fluid signal at fixed radius from tool axis MRIL unaffected by washout less than diam of investigation standard diam = 14 inch slim (10.5 inch) and deep-investigating (18 inch) tools also available gradient magnetic field also enable diffusion measurement (more later on this) Frequency Bandwidth B0(r) B0(r) B o @ 169 Gauss, G 17 Gauss/cm 6” 16” MRIL - Principles and Applications 9/18/2018 ã NUMAR Corp., 1996

Measurement Principle Damaged Zone Sensitive Volume typ. 12 cm Mud Cake MRIL - Principles and Applications 9/18/2018

MRIL - Principles and Applications MRIL in Wellbore Borehole MRIL Probe Sensitive Volume Cylinders (each 1 mm thick at 1 mm spacing) 24 “ This figure illustrates the MRIL tool in the bore hole and the sensitive volumes that are concentric with the tool. The three volumes are actually excited individually with only one volume being measured at a time. After being measured, the protons within a sensitive volume must recover for a period of time. During the recovery time for a given volume, the other volumes are investigated. By cycling between the sensitive volumes the MRIL gathers more data and can log faster than older designs which can only investigate a single volume. 16” MRIL - Principles and Applications 9/18/2018 ã NUMAR Corp., 1995

Using Multiple Frequencies Improves Logging Speed Increases Signal to Noise MRIL - Principles and Applications 9/18/2018

A New Multiband Generation of NMR Logging Tools MRIL-Prime Features 9 discrete measurement volumes Accelerated polarization - 12 sec in 6 sec more robust electronics and new sonde Benefits Single-pass, fast, total porosity & T2 distribution 24 fpm logging speed or Data quality of C tool x 3 Multi-parameter acquisition (T1 curve, etc.) Familiar outputs and interpretation MRIL - Principles and Applications 9/18/2018

MRIL - Principles and Applications MRIL-Prime Shells Borehole 9 Sensitive Volume Cylinders (each 1 mm thick at 1 mm spacing) MRIL Probe 760kHz 580kHz ~1” 24” 16” @ 250°F MRIL - Principles and Applications 9/18/2018

MRIL Diameter of Investigation 6” Probe 20 50° F. 19 100° F. 50° F. 18 150° F. 100° F. 17 200° F. 150° F. Diameter (Inches) 250° F. 16 200° F. 300° F. 15 250° F. 14 300° F. 13 12 500 550 600 650 700 750 800 850 900 950 1000 Frequency (kHz) MRIL - Principles and Applications 9/18/2018

MRIL - Principles and Applications MRIL Calibration Tank Side View End View Formation Chamber Faraday Cage Borehole Chamber MRIL Tool Sensitive Volumes MRIL - Principles and Applications 9/18/2018 ã NUMAR Corp., 1996

MRIL - Principles and Applications T2 Relaxation T 2A 1 2B 2S = + 2D MRIL - Principles and Applications 9/18/2018

Effective Porosity (MPHI) Irreducible (MPHI - MFFI) Idealized Echo Train Effective Porosity (MPHI) Free Fluid (MFFI) Amplitude T2R The resonant signal that is received from the sensitive volume is illustrated above. The initial amplitude represents the effective porosity of the formation and the rates of decay within the signal provide the irreducible and free fluid measurements. The free fluids are generally associated with the slow decaying portion of the measurement while the irreducible fluids are the rapidly decaying portion. The sample rate most commonly used with the MRIL tool is 1.2 milliseconds between samples and is referred to as TE (time between echoes). The rate of decay of the received signal is an exponential time constant and is called T2. After each measurement as shown above, time must be given for the hydrogen protons within the sensitive volume to recover. If sufficient time between experiments is not given, the amplitude of the next measurement will be too low. The rate of recovery of the affected protons is an exponential time constant that is called T1. Bulk Volume Irreducible (MPHI - MFFI) TE MRIL - Principles and Applications Time 9/18/2018 ã NUMAR Corp., 1995

Hydrogen in Matrix & Clay Bound Water Hydrogen in Clay Bound Water This figure amplifies the very early part of the received signal and clearly shows why any hydrogen present in the matrix or in clay bound water are not part of the measurement. Both these components of the signal decay extremely rapidly and are simply no longer present by the first sample taken by the tool. It would be possible to measure the clay bound water by using a sample rate (TE) that is much faster than is currently used. Hydrogen in Lithology MRIL - Principles and Applications 9/18/2018 ã NUMAR Corp., 1995

MRIL - Principles and Applications Pore Size and T2 (Water) T2 time T2 time T2 time T2 time T2 time MRIL - Principles and Applications 9/18/2018

Coarse Grain Response MPHI = 36, MFFI = 30, MBVI = 6, MPERM = 4200 md 40 35 30 25 Porosity 20 15 This figure illustrates the signal as it is received by a tool (x’s). The computer in the up hole unit computes the “best fit” to the data (black line) and provides the components that sum together to equal that best fit line. This example represents a pore system that is dominated by large pores (slow decay - large T2 values). 10 5 50 100 150 200 250 MRIL - Principles and Applications Time (ms) 9/18/2018 ã NUMAR Corp., 1995

Fine Grain Response MPHI = 36, MFFI = 6, MBVI = 30, MPERM = 6.7 md 40 35 30 25 Porosity 20 15 This figure illustrates the signal as it is received by a tool (x’s). The computer in the up hole unit computes the “best fit” to the data (black line) and provides the components that sum together to equal that best fit line. This example represents a pore system that is dominated by very small pores (fast decay - small T2 values). 10 5 50 100 150 200 250 -5 MRIL - Principles and Applications 9/18/2018 Time (ms) ã NUMAR Corp., 1995

MRIL - Principles and Applications MAP Processing Echo 1 = A1e-t/4 + A2e-t/8 + A3e-t/16 + A4e-t/32 + A5e-t/64 + A6e-t/128 + A7e-t/256 + A8e-t/512 + Noise Echo 2 = A1e-t/4 + A2e-t/8 + A3e-t/16 + A4e-t/32 + A5e-t/64 + A6e-t/128 + A7e-t/256 + A8e-t/512 + Noise Echo 3 = A1e-t/4 + A2e-t/8 + A3e-t/16 + A4e-t/32 + A5e-t/64 + A6e-t/128 + A7e-t/256 + A8e-t/512 + Noise Echo n = A1e-t/4 + A2e-t/8 + A3e-t/16 + A4e-t/32 + A5e-t/64 + A6e-t/128 + A7e-t/256 + A8e-t/512 + Noise MRIL - Principles and Applications 9/18/2018 ã NUMAR Corp., 1995

MRIL - Principles and Applications Data Processing MAP “Inversion” Processing Spin-echo data T2 Spectrum NMR porosity 2.00 Free Fluid - FFI 16 multiexponential fit to spin-echo amplitudes 14 1.50 12 Clay Bound Water - CBW Capillary Bound Fluid - BVI large-pore (mobile fluid) signal 10 Incremental Porosity [pu] Invisible Region 1.00 Cumulative Porosity [pu] 8 6 0.50 4 2 time 0.00 0.1 1 10 100 1000 10000 small-pore (irreducible fluid) signal T2 [msec] clay-bound water Water-saturated rock: rT2 = V/S “Invisible Region” is a function of signal to noise and echo spacing MRIL - Principles and Applications 9/18/2018

Spin Echo Attenuation by Diffusion in a Gradient Magnetic Field only stationary spins are completely rephased by p pulses in a CPMG expt spins diffusing in a gradient magnetic field undergo unrecoverable dephasing... Þ echo attenuation Þ transverse relaxation mechanism ..... two sources of magnetic field gradients ..... B0 B0+d B0+2d B0+3d cfluid B0 Grain Rock Grain Pore cgrain Rock Grain 2r pair of cpmg trains at two different TE’s diffusion “propagator” (D/12)(g××G×TE) fixed vs. pulsed field gradient nmr measurement of D Rock Grain Natural ... grain scale gradients arising due to magnetic susceptibility c contrast between minerals and pore fluids ... randomly varying at grain scale pore size and mineralogy dependent Applied ... MRIL uses strong gradient magnetic field to perform “slice selection” ... known, well-defined gradient gives predictable T2 shifts that depend only on diffusion MRIL - Principles and Applications 9/18/2018

MRIL - Principles and Applications Diffusion and T2D only effective for T2 relaxation (not for T1) 12 T 2D D when T2D = D . ( G .  . Te )2 T 2D e when D : Diffusion Coefficient of Fluid (cm2/sec) depends on Temp. (K) & Viscosity G : Magnetic Field Gradient (Gauss/cm) depends on Tool Freq. & Temp.  : Gyromagnetic Ratio (Hz/Gauss) = 4258 for Hydrogen Te : Inter-Echo Spacing (sec.) T 2D G when MRIL - Principles and Applications 9/18/2018

Effect of Oil on T2 Distribution Incremental Porosity % This figure illustrates the effect of oil in a rock sample. Each color indicates a different water saturation on a T2 Distribution. This particular rock sample has a very simple pore size distribution as seen by the white area (100% water saturation). Almost all of the porosity is represented by a narrow band on the T2 scale indicating a very uniform pore size. As oil saturation is increased, the amplitude of the water filled portion of the distribution gets smaller due to the decreased volume of water. As this happens, the oil peak grows in amplitude due to the increasing volume of oil. Also, since the surface to volume ratio of the water signal is changing (same surface area but reduced volume of water) the T2 value for the water filled portion also goes down - decays faster. In other words, when the formation is 100% saturated with water, the T2 value is centered at about 26.6 milliseconds. But when the water saturation is reduced to 56.9% the T2 for the water filled portion is down to 7.4 milliseconds. This explains why the short T2 part of the signal represents the irreducible fluids. The short T2 values represent either fluids that are trapped in very small pores or the water filled part of the porosity that remains when hydrocarbons are present. Note also that the oil signal is very constant with respect to the T2 axis. This is because the system is “water wet” and the oil is not affected by the surface of the rock’s pore system. The oil signal is simply its bulk T2 value (related to viscosity). Sw = 56.9% Sw = 65.4% Sw = 84.3% Sw = 100% T2 Distribution MRIL - Principles and Applications 9/18/2018 ã NUMAR Corp., 1995

Partially Saturated Water Wet Rock Behavior Sw = 100 % T2 T2 Sw < 100 % MRIL - Principles and Applications 9/18/2018

Viscosity & Diffusion vs T2 @ 80 ° F. MRIL - Principles and Applications 9/18/2018 ã NUMAR Corp., 1995

T2 Distributions & Incomplete Recovery The long end of T2 distributions - indicative of hydrocarbons - can be associated with very long T1 times. If standard recovery times TR are used, that portion of a T2 spectrum will be depressed by 50% or more. correct T2 spectrum incomplete recovery P (T2) T2 MRIL - Principles and Applications 9/18/2018 ã NUMAR Corp., 1995

MRIL - Principles and Applications Viscosity vs. T2 for oils 10000 T 2 = 4T / h 1000 T2 (ms) 100 100 F T2cutoff 300 F T2 Oil adopted from Looyestijn et al, 1996 10 10 20 30 40 50 Viscosity (cp) MRIL - Principles and Applications 9/18/2018

MRIL - Principles and Applications Viscosity vs. D0 for oils 0.01 0.1 1 10 100 D = 2.5T / 300 h Diffusion coefficient (x10e -5 cm2/s) 100 F 300 F adopted from Looyestijn et al, 1996 10 20 30 40 50 Viscosity (cp) MRIL - Principles and Applications 9/18/2018

MRIL - Principles and Applications MRIL Response MRIL - Principles and Applications 9/18/2018

MRI Log Processing & Interpretation Conductive Fluids Matrix & Dry Clay Clay Bound Water Capillary Bound Water Moveable Free Water Oil Gas MCBW MPHI MRIL MBVI MFFI PHIT MRIL Porosity MRIL =  . HI . ( 1 – e–tw/T1) MRIL =  . Sxo . HIw . ( 1 – e–tw/T1w) +  . ( 1 - Sxo) . Hlh . ( 1 – e–tw/T1h) MRIL - Principles and Applications 9/18/2018

MRI Log Processing & Interpretation Conductive Fluids Matrix & Dry Clay Clay Bound Water Capillary Bound Water Moveable Free Water Oil Gas MCBW MPHI MRIL MBVI MFFI PHIT MRIL Permeability MRIL - Principles and Applications 9/18/2018

Direct Hydrocarbon Typing Differential Spectrum Method Porosity Long Recovery Time (TR) Brine Gas Oil Short Recovery Time (TR) Difference 1 10 100 1,000 10,000 T2 Time (ms) ã NUMAR Corp., 1995 MRIL - Principles and Applications 9/18/2018

MRI Log Processing & Interpretation T.D.A. MRIL Time Domain Analysis Correcting MRIL Porosity for T1 effects Unique Liquid Phase Porosity TwLu Long Tw Short Tw TwSu 1 10 100 1,000 10,000 T2 Time (ms) MRIL - Principles and Applications 9/18/2018

MRI Log Processing & Interpretation TDA_COMP The Porosity Measured by MRIL is Subject to Hydrogen Index HI and Polarization T1 effects.  Tw =  . HI . ( 1 - e -Tw/T1)  : True Hydrocarbon Porosity Tw : Measured Hydroc. Porosity Tw : Wait Time HI : Hydrogen Index TwLu : Porosity from TwL of unique Fluid phase TwSu : Porosity from TwS of unique Fluid phase TwL : Long Wait Time TwS : Short Wait Time T1 estimation is based on the Ratio r =  TwLu /  TwSu  . HI . ( 1 - e -TwL/T1 ) r =  . HI . ( 1 - e -TwS/T1 ) 1 - e -TwL/T1 = 1 - e -TwS/T1 MRIL - Principles and Applications 9/18/2018

MRI Log Processing & Interpretation TDA_COMP gas is calculated by correcting for HIgas & T1gas g : Gas Porosity g * : Apparent Gas Porosity seen by echo difference HIg : Hydrogen Index of Gas o : Oil Porosity o* : Apparent Oil Porosity HIo : Hydrogen Index of Oil T1h : T1 of either Gas or Oil oil is calculated by correcting for HIoil & T1oil MRIL - Principles and Applications 9/18/2018

[ ] MRI Log Processing & Interpretation TDA_COMP Fully Polarized Liquid Porosity from Long Tw PhiFPL = MPHIA - [ g . HIg . ( 1 - e -TwL / T1g ) + o . HIo . ( 1 - e -TwL / T1o ) +  w . HIw . ( 1 - e -TwL / T1w ) ] Corrected Porosity for T1 and HI TDAMPhi = PhiFPL + g + o +  w MRIL - Principles and Applications 9/18/2018

Direct Hydrocarbon Typing Shifted Spectrum Method Short Echo Spacing Brine Gas Porosity Long Echo Spacing Porosity 1 10 100 1,000 10,000 T2 Time (ms) ã NUMAR Corp., 1995 MRIL - Principles and Applications 9/18/2018

Direct Hydrocarbon Typing Shifted Spectrum Method Short Echo Spacing Brine Oil Porosity Long Echo Spacing Porosity 1 10 100 1,000 10,000 T2 Time (ms) ã NUMAR Corp., 1995 MRIL - Principles and Applications 9/18/2018

MRI Log Processing & Interpretation DIFAN MRIL Diffusion Analysis MRIL data acquired using Dual Te Solves for Oil in the slice under investigation Does not solve for VERY Heavy Oil MRIL - Principles and Applications 9/18/2018