American Oil and Gas Reporter - February 2022 - 59

the SRV. To be an economic target, these
zones need to have the development of
matrix porosity over a contiguous zone
of sufficient thickness, while between
these zones, reservoir quality is typically
much lower, corresponding to much less
moveable fluid. Although the composition
may vary significantly within lower-quality
zones, they ultimately will not contribute
significantly to produced fluids.
In contrast, within target zones that
exhibit contiguous (mappable) matrix
porosity, both oil and water diagenesis
will be subject to similar fluid migration
history, charging, maturity and fluid diagenesis.
In better-quality reservoirs with
FIGURE 4
Water and Oil Allocation TLG Summary Charts
D-1XNH Water Allocation
100%
90%
80%
70%
60%
50%
40%
0%
10%
20%
30%
8_12_19
8_20_19
8_26_19
9_1_19
100%
90%
80%
70%
60%
50%
40%
First Oil Sample
9_13_19
D-1XNH Water Allocation
100%
90%
80%
70%
60%
50%
40%
0%
10%
20%
30%
8_12_19 8_20_19 8_26_19 9_1_19 9_13_19
100.0
90.0
80.0
70.0
60.0
50.0
40.0
0.0
10.0
20.0
30.0
8_8_20
8_10_20
Frac Water
8_14_20
8_21_20
8_28_20
M Turner
9_4_20
9_18_20
U Turner
10_30_20
100%
90%
80%
70%
60%
50%
40%
First Oil Sample
10_4_19 10_16_19 11_20_19 12_18_19 1_15_20 4_17_20 7_13_20
D-1XTH Water Allocation
100.0
90.0
80.0
70.0
60.0
50.0
40.0
0.0
10.0
20.0
30.0
8_8_20
8_10_20
Nio Shale
8_14_20
8_21_20
Nio " C "
8_28_20
9_4_20
9_14_20
Nio " B " Chalk
FEBRUARY 2022 59
9_18_20
0%
10%
20%
30%
10_4_19
10_16_19
11_20_19
12_18_19
W-1XNH Oil Allocation
1_15_20
7_13_20
0%
10%
20%
30%
10_4_19
10_16_19
10_4_19
10_16_19
D-1XNH Oil Allocation
higher productivity, all the factors that
affect fluid diagenesis-whether for oil
or water-lead to more homogenous fluids.
These factors seem to explain why
mixing models of produced fluids generally
are solvable using relatively few endmember
components. Stated another way,
for produced fluid composition, the potential
target zones within the SRV are
dominant, and within these zones, the
moveable fluids are much more homogenous
and lack fine vertical distinctions.
Figure 4 shows water and oil unmixing
results for TLG studies of three wells. In
the first two wells (D-1XNH and D1XTH),
early oil samples were destroyed
during shipment and the green inverted
triangles mark the time on the water allocation
summary chart where the first
oil sample analysis was available. For D1XNH,
the quantity of water had decreased
greatly and was not sampled after Oct.
16, 2019, as shown by the blue inverted
triangle on the oil allocation summary.
The green-filled area of the water allocation
summary corresponding to the Niobrara
Shale composition is probably representative
of both Niobrara A and C formation
waters. In the oil allocation summary
chart, however, the Niobrara C composition
is represented by the olive-green filled
area and the green-filled area corresponds
Last Oil Sample
11_20_19
12_12_19
12_18_19
1_2_20
D-1XTH Oil Allocation
1_18_20
3_18_20
4_6_20
Percent (%)
Percent (%)
Percent (%)
Percent (%)
Percent (%)
Percent (%)
American Oil and Gas Reporter - February 2022

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