NMR logging uses nuclear magnetic resonance to infer properties of rock formations such as porosity, permeability, and fluid distributions. It works by applying a magnetic field to align hydrogen proton spins, then measuring the decay of the signal as the spins relax. This decay provides information about pore sizes and fluid types. Main advantages are lithology-independent porosity and improved permeability estimates compared to conventional well logs. Limitations include cost, speed, and shallow depth of investigation. Recent advances aim to improve resolution and differentiate fluid and rock properties.

1. BY MARIE WALKER

2. • Introduction
• Principles of NMR
• Interpretations of Raw Data
• The NMR Log
• NMR Tools
• Advantages and Disadvantages of NMR Logging
• Advances in NMR Logging
• Future of NMR Logging
• Summary

3. • Nuclear Magnetic Resonance (NMR) is the phenomenon
whereby a magnetic nuclei absorbs and emits energy in the
presence of a magnetic field
• The first NMR Logging Tools were developed in the early
1960’s
• Plagued with problems so it was retired in the 1980’s
• Re-emerged with the advent of pulsed tools
• NMR allows for the calculation of:
 Porosity
 Permeability
 Pore-space distributions
 Producible fluids and Irreducible Fluids
 Reservoir Quality
 Hydrocarbon Quality

4. • All subatomic particles (neutrons, protons, electrons)
have the intrinsic property of spin
• This spin corresponds to a small magnetic moment
• In the absence of a magnetic field the moments are
randomly aligned
• When a static magnetic field, Bo is applied this field acts
as a turning force that aligns the nuclear spin axis of
magnetic nuclei with the direction of the applied field

5. • When a torque is applied to a spinning object, the
axis of the object moves perpendicularly to the
applied torque in motion called precession
• So the nucleus will precesses around Bo with a
frequency called the Lamour frequency
• This proton can be in 2 energy states depending
on the orientation of the axis
• The difference between the number of protons in
each state gives the bulk magnetization which
provides the signal measured by NMR devices

6. • The alignment of these protons is called polarization but
this does not happen immediately it grows with a time
constant called longitudinal relaxation time T1
• After T1 an oscillating magnetic field is applied, sending
pulses of radio-frequency energy into the formation
• The initial pulse is perpendicular to Bo and aligns the
spins in the transverse direction in phase with one
another
• As the pulse dies, the magnetisation caused buy the
precession decreases as the spins return out of phase
and the signal seen in the receiver decays
• This very rapid decay is referred to as free induction
decay (FID)

7. • To re-phase the protons a 180° pulse can be applied
• This pulse re-energizes the spins until a peak
magnetization signal is achieved called a spin echo.
• A series of these 180° pulses is sent into the formation at
a fixed time interval called TE
• The spin echo signal decreases with each pulse.
• This decay of the series called a CPMG series (Carr-
Purcell-Meiboom-Gill) is referred to as transverse
relaxation time, T2

8. • Total Porosity
 Initial amplitude of the decay curve is a measure of
the amount of polarized hydrogen in the pore fluid
• Pore size distribution
 T2 is smaller at surface area of grains than in pore
space therefore smaller T2 values mean smaller
grain sizes
• Producible porosity and Bulk Volume Irreducible
 Assuming that producible fluids reside in large pores
and non-producible in small pores, T2 distribution
curves can give the values for producible porosity of
a formation

9. • Permeability
 Based on scientific models that show permeability
increases with porosity combined with core data
• PropertiesCoates Model:
of Reservoir Fluids
 Based on T1 and T2 times which indicates pore
sizes. Clay-bound water, capillary-bound
water,Perm= [total brine, hydrocarbons can all be
movable water,
differentiated based 2(producible sizes
porosity/C) on various pore
porosity/Bulk irreducible
volume)]2

10. The NMR Log
Sandy
Interval

11. • Introduced by Numar in 1991
• Composed of a permanent magnet and antennae
• Magnet generates a static magnetic field
• Antennae sends bursts of radio-frequency energy into the
formation in the form of an oscillating magnetic field
• Antennae acts as a receiver for decaying echo signal

12. • Introduced by Schlumberger in 1995
• Uses a bowstring to press against borehole
• Antennae sandwiched between two permanent magnets
• Creates a sensitive zone of about 6 by 1 inches in the
formation
• Used for high resolution data and high-precision

13. • Only fluids are visible to NMR technology
so porosity measurement is independent of
the lithology
• Producible zones with high percentage of
clay-bound water can be identified
• A better measurement of permeability is
possible than traditional plots
• In-situ measurement of oil viscosity
• Differentiation of oil/gas zones

14. • Any diamagnetic or paramagnetic ions present
in the formation can affect the tool response
• Expensive
• Slower logging speeds
• Slimhole tools are not available
• Shallow depth of penetration
• Permeability measurement is actually an
empirical measurement and should only be
used to compare to permeabilities

15. • Schlumberger MRX eXpert
 Contains multiple antennae that enable multiple
depths-of-investigation over a broad range and it
has a magnetic field gradient
 Eliminates the need for multiple passes through
zones of interest
 Suitable for carbonate formations and low-resistivity
pay zones

16. • High- Resolution NMR- allows for the evaluation of
producibility of thinly laminated beds
• Lithology Independent NMR Total Porosity- NMR is the most
accurate tool for measuring the porosity of heterogeneous
formations
• Density/ Magnetic-Resonance Method- combines density and
NMR log to predict gas-bearing formation total porosities
• Multi-dimensional NMR Fluid Characterization- composes 2D
and 3D maps used to visually identify fluids present in the
reservoir on the basis of contrasts in relaxation time

17. • Imaging reservoirs the same way MR is used to image
the human body
• Inferring rock wettability from NMR
• Pressure/Volume/Temperature properties of reservoirs
• Define rock/pore-space connectivity and structure

18. • NMR Logging uses the energy given off from
hydrogen protons as they precess in a magnetic
field to infer measurements of a formation’s
porosity, permeability, pore space distribution, etc.
• Logs can be used to interpret zones of high
porosity and producibility
• Main tools used are the Halliburton’s MRIL and
Schlumberger’s CMR tool
• Gives lithology independent porosities but is more
expensive than conventional tools

20. • Coates, G. R., Xiao, L. and Prammer, M. G. - NMR
Logging Principles and Applications
• Darling, Toby-Well Logging and Formation Evaluation
• David Allen et al- Trends in NMR Logging
• David Allen et al- How to Use Borehole Nuclear Magnetic
Resonance
• Ellis, Darwin V. and Julian M. Singer- Well-Logging for
Earth Scientists
• Freedman, Robert- Advances in NMR Logging