Page 264 - Geology of Carbonate Reservoirs

FRACTURED RESERVOIRS 245

Ridl 19–1
T 140 N
Jilek 1–29
JV-P Elbert 1
Frenzel 79 Filipi 76 Dickinson
Duck Creek Karsky 35–2 State 74
Kadrmas 36–1 Kadrmas 75 Lodgepole Unit
Steffan 1–35
State A-83
Walton 84
Gerber 1–6
Kadrmas 3–1 Steffan 2–2
Shjeflo 1–6 Northland 1–5
Privratsky 77 Hiline
Knopik 1–11 Dinsdale 1–10 Field
LR 1–10 Privratsky 2–12
Ridl 1–11 Privratsky 12A–3
RG 1–10
KR 1–11 JN Patterson
Eland Lake 31–13 Kestling 1+17 Julie 1–14
Dvorak 16–1 Gress 1–14 T 139 N
Steffan 1–14 MOI Fee 44–13 Binek 1–18 R 95 W
Hondl 15–1
Gruman 20–2
Kudma 1–21 Klein 1–23
Ranchos 2–24
Frochlich 1–19
Roller 1–24 Schmaltz 1–20
T 139 N Haller 1–29
Patterson 1–24 Gruman 20–1
Hondl 30–1 Krank 1–28 Wolf 28–1
Haller 29–1
Dobson 50°
Saskatchewan Manitoba
Butte F.
Dvorak 43–31 (Silurian) Canada
Dvorak 34–1
Fromberg+Brockton Fault Z
Kostelecky 1–32
Airport 32–4 Nesson
Vogel 11–3 Anticline 48°
Veverka 5–1 Anticline Little North Dakota
Billings
Anticline
Cedar Creek Knife Lodgepole
0 1 mi Anticline Play Area
Montana
Discovery well 46°
Lemmon
0 1 km
Anticline
Williston
T 138 N Margin
Basin
Black
0 50mi
Hills
R 97 W R 96 W 0 50 km Uplift 44°
Wyoming South Dakota
100° 100°

Figure 8.17 Location of the Dickinson area fields, Williston Basin, North Dakota. Note that

there are nine individual fields encompassing several large “ reef mounds. ” (From Mont-

gomery ( 1996 ).)
1000 BOPD and individual wells may produce over 1 million barrels of oil. Primary

recovery has been estimated to be about 28% with original oil in place calculated
to be between 70 and 100 million barrels. The Lodgepole mounds produce from
moderately low porosity (average 5%), which consists of a complex mixture of
depositional, diagenetic, and fracture pore types (Figure 8.18 ). Depositional porosity
consists mainly of stromatactoid vugs in the mounds and grainstones interbedded
within the mound complex. Diagenetic porosity includes leached interparticle
porosity in grainstones and rather extensive burial dissolution that enlarged vugs
and fractures within the mudstone and wackestone mound facies. Vugs and fractures

enlarged by late dissolution are also commonly filled or partly filled with saddle
dolomite, similar to the type observed in the Hardeman Basin wells discussed
earlier, although the stromatactoid vugs in the Dickinson mounds are rare in the
Hardeman Basin examples. Fractures are common in whole cores from Dickinson

area wells, they are recognized on image logs, and by their influence on reservoir
performance pressure transient testing.
Several types of fractures exist in the Dickinson mounds and they formed at dif-
ferent times during mound burial history and subsequent tectonism. Compaction
fractures are common in the thin - bedded, lower mound zones where the mound