Is NMR technology used anywhere against laminated reservoirs keeping in view of the vertical resolution of different tools in the industry?
AK Saikumar Kakani
Advisor-Petrophysics, HLS Asia Ltd, Independent Petrophysics Consultant
Thanks to all for your valuable inputs. I have another question. If we are using a mandrel type of tool one being centered and another eccentered what will be affect of Te?
For ex: If I use Te of 3.6 ms in case of centred tool, will the same Te give the same results in case of eccentered tool?
I feel it will not be same…In that case whether Te should be higher in case of eccentered tool? Appreciate your explanation on this
Virtual PPS Reply
Forward model T2 CPMG single relaxation time of 1 msec.
Note: This example is theoretical and does not contain noise.
This was chosen as a sensitivity of the impact of tool TE in fast relaxing formations, i.e. shale.
The three figures below represent a T2 decay for the current commercial logging tools with minimum TE values of 0.2, 0.6 and 1.2 msec respectively.
Firstly, the impact of TE can be seen by the amplitude of the first echo relative to the 30% porosity modelled formation: 82%, 55% and 30% for the three figures.
What if: Processing the data excluding echo 1? Then the second echo amplitude relative to the formation porosity is 67%, 30% and 9% of the porosity. A long way from the starting amplitude.
In carbonate formations with low surface relaxivity, there will not be much sensitivity, or missing porosity due to running tools with higher Te. However in clastics with a proportion of clay minerals, it is likely there will be missing short (fast) T2 components resulting in a porosity lower than the formation porosity with these higher Te tools.
Figure 1, Te 0.2msec, T2 1msec: CMR+
Figure 2, Te 0.6msec, T2 1msec: MREX, MagTrak(lwd), ProVision+(lwd)
Figure 3, Te 1.2msec, T2 1msec: MRIL Prime, MRILWD
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