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
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
19.
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
