### T 2 – Relaxation time

```Strata Exploration, Inc.
Nuclear Magnetic Resonance Solutions
of Low Resistivity Pay
Charles H. Smith and
Layne Hamilton, Halliburton;
John R Kinney II, Strata
Exploration; Jon Christensen and
George A. Payne, Consultants
Solids….invisible to MRI
Fluids
irreducible moveable
water
clay bound
rock matrix
dry clay
oil
clay bound
T2 Relaxation
T1 Magnetization
0
1
2
3
4
5
6
time, sec.
8 9 10
11
12
13
14 …….
T2 – Relaxation
time
16 ms
Incremental Porosity %
100
80
60
40
20
0
0
100
200
300
400
T (ms)
Small pores and large pores all contribute to early time response
500
T2 – Relaxation
time
128 ms
Incremental Porosity %
100
80
60
40
20
0
0
100
200
300
T (ms)
400
500
T2 – Relaxation
time
8000 ms
Incremental Porosity %
100
80
60
40
20
0
0
100
200
300
400
500
T (ms)
Conclusion: To get a description or T2, you must measure a total of 8 seconds
- Distribution of the pores will affect ability of the reservoir to produce
T2 Bray-Smith Permeability Equation
T 2 Bphi 2048 ms


p
Bray  Sm ith Perm  MPHI  * (  wf * T Bphi/ BVI)
2


T 2 Bphi 4 ms
• Where :
Bray-Smith Perm = Bin calculated Permeability,
MPHI = NMR effective porosity,
wf = Bin weighting factor,
Bphi = Bin porosity
BVI = Irreducible porosity fraction.
Factors p and s are empirically derived constants
s
Solids….invisible to MRI
irreducible moveable
water
clay bound
rock matrix
dry clay
Very early time = clay
bound
Fluids
OIL
Early time = BVI
Middle time = free water
clay bound
Later time =
hydrocarbon
T2 Relaxation times
T1 Magnetization
0
1
2
3
4
5
6
time, sec.
8 9 10
11
12
13
14 …….
T1 is much less sensitive to fluid type – alignment time defines fluid type
Oklahoma MRIL Log Presentation
Big Bin Ratio
Oil Line
Big Bin Ratio Perm
2006 - 2008 Planning
Framework
11
Gas Line
T1 Hydrocarbon
Curve
Tool Comparison
Data volume acquired
Pad-Based NMR single sensitive volume ~ 43 cc
Mandrel-based NMR single sensitive volume ~ 778 cc
If all else is equal – a mandrel-based NMR acquires
18 times as much data as a pad-based design
Tool Comparison
Data volume acquired
Pad-Based NMR single sensitive volume ~ 43 cc
Mandrel-based NMR single sensitive volume ~ 778 cc
If all else is equal – a mandrel-based NMR acquires
18 times as much data as a pad-based design
When logging speed is increased, all else is not
equal! The ratio gets larger
NMR logs very slowly for T1- requires 12
seconds
T2 requires 8 seconds of measurement
Carbonate Section with Oil/Water
Contact
OIL
WATER
NO RESISTIVITY CHANGE
Carbonate Section with Transition
from Water to Hydrocarbon
TRANSITION TO HYDROCARBON
NO RESISTIVITY CHANGE
Miss Completion
DST 4718-4754. Rec 340 feet of gas in pipe w/oil flecks
Kinderhook Completion
DST . 4788-4802. Rec 95 feet gas in pipe, free oil on top of tool
Completed here, IP = 170 MCFD, 2-3 BOPD and 150 BWPD
Miss Completion
DST . 4792-4812. Rec 2340 feet GIP, trace of oil
Completed 4792-4812, IP 35 Bbl/day, produce 5 Bbl/day
Miss Completion
TCP Perforate 4804-4814. Test flowed 5 Bbl/hour. Production rate = 80
Bbl/day water free
Miss Completion
DST . 4786-4806. GTS in 4.5 min, oil to surface
Completed 4796-4806, IP 200 Bbl/day oil
Conclusions
• NMR data can be utilized to provide accurate
effective porosity and permeability
– Application of Bray-Smith permeability
• NMR T1 data can be used to indicate fluid type
independent of resistivity
```