Chapter 6Williston Basin Province—Interpretation of 2-D Seismic Data, Mountrail County, North Dakota

By Lawrence O. Anna, John J. Miller, and Ofori N. Pearson

Chapter 6 of 7 Assessment of Undiscovered Oil and Gas Resources of the Williston Basin Province of North Dakota, Montana, and South Dakota, 2010 By U.S. Geological Survey Williston Basin Province Assessment Team

U.S. Geological Survey Digital Data Series DDS–69–W

U.S. Department of the InteriorU.S. Geological Survey

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U.S. Department of the InteriorKEN SALAZAR, Secretary

U.S. Geological SurveySuzette M. Kimball, Acting Director

U.S. Geological Survey, Reston, Virginia: 2013

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Suggested citation: Anna, L.O., Miller, J.J., and Pearson, O.N. 2013, Williston Basin Province—Interpretation of 2-D seismic data, Mountrail County, North Dakota, chap. 6 of U.S. Geological Survey Williston Basin Province Assessment Team, Assessment of undiscovered oil and gas resources of the Williston Basin Province of North Dakota, Montana, and South Dakota, 2010 (ver. 1.1, November 2013): U.S. Geological Survey Digital Data Series 69–W, 6 p.

iii

Contents

Introduction.....................................................................................................................................................1Interpretation ..................................................................................................................................................1Seismic Reflection Data Acquisition and Processing .............................................................................1

Data Acquisition ....................................................................................................................................1Data Processing ....................................................................................................................................1Identification of Reflectors ..................................................................................................................2

Acknowledgments ........................................................................................................................................6References Cited............................................................................................................................................6

Figures 1. Seismic lines, major producing areas, and major lineaments ..............................................2 2. Seismic line 100-14 Synthetic and includes synthetic seismogram .....................................3 3. Seismic line 100-14W/100-14E ....................................................................................................3 4. Seismic line 100-9 .........................................................................................................................3 5. Seismic line NEW-228 ..................................................................................................................4 6. Seismic line GR-414 ......................................................................................................................4 7. Seismic line 100-13 .......................................................................................................................5

Table 1. Seismic acquisition parameters .................................................................................................5

Introduction

Six seismic reflection lines from Mountrail County, N. Dak., were acquired to document the relation between mapped surface lineaments and to interpret structure related to oil and gas production. The longest line, 100-14W/100-14E, extends east–west over the Parshall producing area (fig. 1), which produces from the Bakken Formation. Line 100-14E is an eastern extension of line 100-14W and extends over Plaza and Wabek fields that produce from the Mississippian Mission Canyon Formation. Both lines were merged during reprocess-ing (fig. 1). Line 100-9 is a north–south line that ties with lines 100-14E and 100-14W. Lines NEW-228, GR-414, and 100-13 (fig. 1) were used to supplement structural and stratigraphic interpretations of the study area.

Interpretation

The history of the Precambrian basement of the Williston Basin is critical to understanding the basin’s evolution, struc-tural configuration, and sedimentation and thermal patterns. Geophysical methods used to map Precambrian structures include gravity and magnetic surveys, which define large- scale Precambrian fault blocks (Brown and Brown, 1987; Anna, 1986) including their orientation and block length that are important attributes to help interpret structural and sedi-mentation trends. Seismic data were used to refine the gravity and magnetic interpretations. Interpretation of the six, two-dimensional (2-D) seismic lines included the delineation of the Red River Formation, Bakken Formation, Madison Group, and Spearfish Formation (figs. 2–7), and the mapping of numerous faults, most of which are thought to be rooted in Precambrian basement. These faults were interpreted as approximate or inferred because net offsets are small and are difficult to map at the seismic scale. There is also uncertainty as to how far the faults propagate upward through the stratigraphic section. A minor number of structural anomalies may be attributed to salt dissolution.

The positions of the Stanley and Lonetree-Glenburn lineaments (fig. 1) (Anna, 1986) are interpreted from seis-mic lines, as well as the location of two major producing areas in Mountrail County, N. Dak. (North Dakota Oil and Gas Commission, 2009). Although the Parshall and Sanish producing areas straddle the two lineaments, it is unclear if the lineaments create an area of enhanced reservoir quality. Later-als from horizontal wells trend northwest–southeast, which indicates that operators are attempting to intercept northeast–southwest structural features.

Seismic Reflection Data Acquisition and Processing

Data Acquisition

The seismic data consist of six multichannel seismic reflection lines that the U.S. Geological Survey (USGS) purchased by contractual agreement from Seitel Data, Ltd., in 2007. Two of the lines (100-14W and 100-14E) were combined during reprocessing and interpreted as a single line (line 100-14W/100-14E; fig. 3). The data were originally acquired between 1974 and 1984 by Pacific West Exploration Company, Kemp Geophysical Corp., and Sefel Geophysical, Ltd. (table 1). The lines form a loose network covering a large part of Mountrail County, N. Dak. In total, 67 line-miles of data were purchased. The acquisition agreement for these data by the USGS included limited publication rights. Table 1 gives the field acquisition parameters for all of the lines.

Data Processing

The seismic reprocessing by the USGS was conducted to emphasize reflectors in the sedimentary column and to convert the seismic time structure into depth coordinates. This reprocessing consisted of a standard sequence of (1) auto-matic gain-control scaling, single-design window-spiking

Williston Basin Province—Interpretation of 2-D Seismic Data, Mountrail County, North Dakota

By Lawrence O. Anna, John J. Miller, and Ofori N. Pearson

2 Williston Basin Province—Interpretation of 2-D Seismic Data, Mountrail County, North Dakota

Plaza and Wabekfields

INSET MAP

SD

MT ND

Parshallproducingarea

Sanishproducingarea

Synthetic welllocation

102°

48°

NEW-228

100-

9

100-14E100-14W/GR-414

100-

13

MOUNTRAIL COUNTY

100-14 Synthetic

Stanley lineament

Lonetre

e-Glenburn lin

eament

{

Figure 1. Seismic lines, major producing areas, and major lineaments. Inset map is the Williston Basin Province. Line 100-14 Synthetic is a shortened version of line 100-14W/100-14E as shown by the brace.

deconvolution, datum statics using smoothed surface eleva-tions, velocity analysis, and surface-consistent residual statics; (2) a second velocity analysis; (3) normal move-out and stack; (4) shift to a horizontal datum equal to the average elevation of the line; (5) migration using a smoothed stacking velocity field and automatic gain control scaling; and (6) second-zero-crossing predictive deconvolution, and bandpass filter. Depth conversion was performed using the same smoothed stacking velocity field used for migration. After depth conversion, all seismic lines were shifted to an elevation datum of 2,100 ft above sea level.

Because the seismic lines were recorded by different companies, using different energy sources and recording parameters, the processing parameters used for each line were data dependent and were selected based on exten-sive testing. For example, the seismic energy sources were Vibroseis, dynamite, and land airgun (table 1), which made it necessary to vary deconvolution and bandpass filter parameters significantly. Another problem we encountered was that, although lines 100-14W and 100-14E overlapped, they were recorded in different years using a different

geophone group interval, which resulted in different horizontal trace spacing. Migration requires constant trace spacing, so to solve this problem each line was processed separately up to the point of migration and then combined. Before combining the lines, the trace spacing of line 100-14E was adjusted to match that of 100-14W by means of a Fourier trace interpola-tion algorithm. This allowed us to migrate the combined lines as a single line.

Identification of Reflectors

To tie the seismic data to well data, we created a synthetic seismogram using a sonic log recorded in Lear Petroleum, #1 School District, located in T. 152 N., R. 90 W., sec. 3. The location of this well is about 52,800 ft east of the west end of line 100-14W and a few feet north of the line at the loca-tion shown on figure 1. We were able to identify reflectors with a high degree of confidence between 3,500 and 12,500 ft depths. The synthetic seismogram was embedded in line 100-14 Synthetic (figs. 1 and 2), a shortened version of line 100-14W/100-14E (figs. 1 and 3).

Seismic Reflection Data Acquisition and Processing 3

Figure 2. Seismic line 100-14 Synthetic and includes synthetic seismogram. This west–east line includes part of line 100-14W/100-14E. Red lines are interpreted faults. (Click here to open full-size, high-resolution image.)

0

2,500

5,000

7,500

10,000

12,500

15,000

17,500

0

2,500

5,000

7,500

10,000

12,500

15,000

17,500

ShotCMP

ShotCMP

260520

270540

280560

290580

300600

310620

320640

330660

340680

350700

360720

370740

380760

390780

400800

410820

420840

EASTWEST

Red River Formation

Bakken Formation

Madison Group

Spearfish Formation

SyntheticLear Petroleum

Parshall School District #1T. 152 N., R. 90 W., sec3

Appr

oxim

ate

Dept

h, in

feet

0 miles 12 miles6 miles3 miles 9 miles

Figure 3. Seismic line 100-14W/100-14E. This west–east line is combined from line 100-14W and line 100-14E and ties with line 100-9. Red lines are interpreted faults. (Click here to open full-size, high-resolution image.)

Figure 4. Seismic line 100-9. This north–south line ties with Line 100-14W/100-14E. Red lines are interpreted faults. (Click here to open full-size, high-resolution image.)

ShotCMP

ShotCMP

170340

180360

190380

200400

210420

220440

230460

240480

250500

260520

270540

280560

290580

300600

310620

320640

330660

340680

350700

360720

370740

380760

390780

400800

410820

420840

430860

440880

450900

460920

470940

480960

490980

5001000

5101020

5201040

5301060

5401080

5501100

5601120

5701140

5801160

5901180

6001200

6101220

6201240

6301260

6401280

6501300

6601320

6701340

6801360

6901380

7001400

7101420

7201440

7301460

7401480

7501500

7601520

7701540

7801560

7901580

O-100 14syntheticO-100 14synthetic O-100 14synthetic O-100 14syntheticO-100 14synthetic O-100 14synthetic O-100 14syntheticO-100 14synthetic O-100 14synthetic O-100 14synthetic O-Line 100 9

Red River Formation

Bakken Formation

Madison Group

Spearfish Formation

Red River Formation

Bakken Formation

Madison Group

Spearfish Formation

Appr

oxim

ate

Dept

h, in

feet

Line

100

-9 T

ieSyntheticInserted

Here0 miles 37 miles18.5 miles14 miles 28 miles0

2,500

5,000

7,500

10,000

12,500

15,000

17,500

0

2,500

5,000

7,500

10,000

12,500

15,000

17,500

EASTWEST

Amplitude

ShotCMP

ShotCMP

210420

220440

230460

240480

250500

260520

270540

280560

290580

300600

310620

320640

330660

340680

350700

360720

370740

380760

390780

400800

410820

420840

430860

440880

450900

460920

470940

480960

490980

5001000

5101020

5201040

5301060

5401080

5501100

5601120

5701140

5801160

5901180

6001200

6101220

6201240

6301260

6401280

6501300

6601320

6701340

6801360

B

O-100 14wext and 100 14a combined

Spearfish Formation

Madison Group

Bakken Formation

Red River Formation

Spearfish Formation

Madison Group

Bakken Formation

Red River Formation

NORTH SOUTH20 miles0 miles 15 miles10 miles5 miles

Appr

oxim

ate

Dept

h, in

feet

0

2,500

5,000

7,500

10,000

12,500

15,000

17,500

0

2,500

5,000

7,500

10,000

12,500

15,000

17,500

4 Williston Basin Province—Interpretation of 2-D Seismic Data, Mountrail County, North Dakota

Figure 6. Seismic line GR-414. Red lines are interpreted faults. (Click here to open full-size, high-resolution image.)

ShotCMP

ShotCMP

230460

240480

250500

260520

270540

280560

290580

300600

310620

320640

330660

340680

350700

360720

Spearfish Formation

Madison Group

Bakken Formation

Red River Formation

Spearfish Formation

Madison Group

Bakken Formation

Red River Formation

NORTHWEST SOUTHEAST

0 miles 9.5 miles7.1 miles4.75 miles2.4 miles

Appr

oxim

ate

Dept

h, in

feet

0

2,500

5,000

7,500

10,000

12,500

15,000

17,500

0

2,500

5,000

7,500

10,000

12,500

15,000

17,500

Figure 5. Seismic line NEW-228. Red lines are interpreted faults. (Click here to open full-size, high-resolution image.)

ShotCMP

ShotCMP

13102620

13202640

13302660

13402680

13502700

13602720

13702740

13802760

13902780

14002800

14102820

14202840

14302860

14402880

14502900

14602920

14702940

14802960

14902980

15003000

15103020

15203040

15303060

15403080

15503100

Spearfish Formation

Madison Group

Bakken Formation

Red River Formation

Spearfish Formation

Madison Group

Bakken Formation

Red River Formation

NORTHWEST SOUTHEAST0 miles 5.0 miles3.75 miles2.5 miles1.25 miles

Appr

oxim

ate

Dept

h, in

feet

0

2,500

5,000

7,500

10,000

12,500

15,000

17,500

0

2,500

5,000

7,500

10,000

12,500

15,000

17,500

Seismic Reflection Data Acquisition and Processing 5

ShotCMP

ShotCMP

7401480

7501500

7601520

7701540

7801560

7901580

8001600

8101620

8201640

8301660

8401680

8501700

8601720

8701740

Spearfish Formation

Madison Group

Bakken Formation

Red River Formation

Spearfish Formation

Madison Group

Bakken Formation

Red River Formation

NORTH SOUTH

0 miles 5.0 miles1.25 miles 2.5 miles 3.75 miles

Appr

oxim

ate

Dept

h, in

feet

0

2,500

5,000

7,500

10,000

12,500

15,000

17,500

0

2,500

5,000

7,500

10,000

12,500

15,000

17,500

Figure 7. Seismic line 100-13. Red lines are interpreted faults. (Click here to open full-size, high-resolution image.)

Table 1. Seismic acquisition parameters.

LineShotpoint number

Geophone interval

(ft)

Trace interval

(ft)

Line length

(mi)

Energy source

Sub- surface

fold

No. of channels

Year recorded

Company

GR-414 235–363 330 165 9 land airgun 18 36 1983 Kemp100-9 656–215 220 110 20.08 dynamite 6 48 1977 Pac West100-13 877–747 220 110 6.16 dynamite 6 48 1977 Pac West100-14E 2,274–2,171 165 82.5 3.25 dynamite 6 48 1979 Pac West100-14W 164–716 220 110 23.0 dynamite 6 48 1974 Pac West100-14 (E & W combined) 110 26.25 dynamiteNEW-228 1330–1520 110 55 5.34 Vibroseis

8–100 hz30 120 1984 Sefel

6 Williston Basin Province—Interpretation of 2-D Seismic Data, Mountrail County, North Dakota

AcknowledgmentsWe thank Walt Johnson (Exploration GeoConsultants,

Inc.) for creating the synthetic seismogram and Kristen Lewis and Warren Agena (USGS) for their technical reviews.

References CitedAnna, L.O., 1986, Geologic framework of the ground water

system in Jurassic and Cretaceous rocks in the Northern Great Plains, in parts of Montana, North Dakota, South Dakota, and Wyoming: U.S. Geological Survey Professional Paper 1402–B, 36 p.

Brown, D.L., and Brown, D.L., 1987, Wrench-style deformation and paleostructural influence on sedimenta-tion in and around a cratonic basin, in Peterson, J.A., Kent, D.M., Anderson, S.B., Pilatzke, R.H., and Longman, M.W., eds., Williston Basin: Anatomy of a cratonic oil province: Rocky Mountain Association of Geologists, p. 57–70.

North Dakota Oil and Gas Commission, 2009, Production map: North Dakota Oil and Gas Commission Department of Mineral Resources, Oil and Gas Division database, available at http://www.dmr.nd.gov/oilgas/feeservices/ getlogs.asp.

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