Page 125 - Fundamentals of Gas Shale Reservoirs

DISCUSSION 105
8 9 10
0.15
Normalized PV 0.1

0.5

0 0
12 13 14
0.15
Normalized PV 0.05
0.1

0 17 18 20
0.15
Normalized PV 0.05
0.1

0 21 23 0 24
0.15
Normalized PV 0.05
0.1

0 25 26 0 27
0.15
Normalized PV 0.05
0.1

0 0 0
0.01 1 100 0.01 1 100 0.01 1 100
Pore diameter (
m) Pore diameter (
m) Pore diameter (
m)
FIGurE 5.27 Pore diameter: NMR T ‐equivalent pore diameter extracted from Equation 5.13 and MICP pore diameter for selected gas
2
shale samples.
compared to the MICP‐derived result (Table 5.6). However,
1
MICPequiv T 2 c (5.15) a good trend was observed between MICP and NMR
SV)
2 (/ (Fig. 5.29).
The advantages of predicting capillary pressure from
3. Plot NMR T versus the weighted incremental pore NMR is that the capillary pressure readings can be continu­
2
volume (from NMR) and the MICP Pc‐equivalent T ously determined with depth (Volokitin et al., 2001), and
2
versus the normalized intrusion volume (from MICP) permeability models requiring capillary pressure can be
on the same plot. used to estimate permeability. The method is also nonde­
structive compared to MICP. On the other hand, deriving the
P MICPTh is the threshold pressure from MICP, P NMRTh is the T relaxation time from MICP data brings certain advan­
2
threshold pressure from T equivalent pressure, ρ is the sur­ tages, particularly in cases where it is difficult to obtain suit­
2
2
face relaxivity, and b and c are shifting factors. able core plugs for evaluating petrophysical properties of
For the majority of the samples, threshold pressure from reservoir rocks. The MICP technique measures the pore
the NMR‐derived capillary pressure was slightly higher volume directly and only requires a small rock cutting or