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£¤52

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UV5

UV50

UV5

UV28 UV256

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North Da kota Geologica l SurveyGeologic Investigation No. 211

Adjoining 100K Maps

Inyan Kara Sandstone Isopach MapMohall 100K Sheet, North Dakota 2017 Ma gnetic North

Declina tion a t Center of Sheet

6o 38'

Edw ard C. Murphy, Sta te GeologistLynn D. H elms. Director Dept of Minera l R esources

2018INTRODUCTION

THE DAKOTA GROUP

Merca tor P rojection Sta nda rd P a ra llel 48°30'0"N

North America n 1983 Da tum Centra l Meridia n 101°30'0"W

0 1 2 3 4

Miles

Ma p Sca le 1:100,000

ISOPACH OF INYAN KARA FORMATION SANDSTONES

Mohall 100K Sheet, North Dakota

Jeffrey W. BaderTravis D. Stolldorf

Kenm are Bottineau

Stanley Minot Velva

CONTROL WELL TYPES/RESERVOIR QUALITY

!(

W ell/Sa ndstone > 100 ft < 5% very fine sa nd to silt,a nd/or la tera lly continuous

!(

W ell/Sa ndstone 50-100 ft, 5-10% very fine sa nd to silt,a nd/or la tera lly continuous

!(

W ell/Sa ndstone 5-50 ft, 10-20% very fine sa nd to silt,a nd/or la tera lly discontinuous

Significa nt volumes (> 1-million barrels/day) of co-produced water are genera ted da ily during productionopera tions for oil a nd gas in North Dakota . Most produced wa ter is brine (sa ltw ater), with very highconcentrations of tota l dissolved solids. P roduced wa ter ha s historica lly been considered a wa ste in the oil a ndgas industry. Subsurfa ce injection is the industry-preferred a lternative for produced water disposa l. Becauseproduced water is brine, produced wa ter disposa l wells are referred to a s sa lt water disposa l wells (SW Dwells).

Geology of the area is the major fa ctor in determining if injection is a via ble option for produced waterdisposa l. The W illiston Basin of North Dakota has a n idea l sequence of geologic units (Dakota Group) presentat a n optima l depth for produced wa ter disposa l. The low er Creta ceous Dakota Group consists of fourformations in descending order (see Cross-Sections A-A' and B-B'):

• Mowry Formation - marine sha le• Newcastle Forma tion - margina l marine sandstone• Skull Creek Forma tion - marine sha le• Inyan Kara Formation - margina l marine a nd non-marine sa ndstone and sha le

O verlying the Dakota Group are severa l thousa nd feet of Creta ceous marine deposits including the P ierreFormation, a very thick, impermea ble sha le. The Jurassic Swift Formation uncomformably underlies theDa kota Group a nd consists of margina l marine sha le with interbedded limestone. The Dakota Group isa pproxima tely 570 ft (175 m) thick at depths of approximately 2,650-3,220 ft (810-980 m) in the center of theMoha ll 100K Sheet.

These Creta ceous a nd Jura ssic units provide a complete succession of rocks for produced water injection. O fspecific importance is the Inyan Kara Formation, which consists of sandstones a nd sha les deposited in incisedva lleys a long the coastline of the Creta ceous W estern Interior Sea w ay. These va lleys were cut by north-northwesterly flowing rivers that dra ined into the sea w a y from highla nds in southern North Dakota, Minnesota ,and Ca na da. The va lleys formed as the Creta ceous seaw ay regressed from North Dakota twice over a period ofa pproxima tely 10 million years. The sea w ay tra nsgressed ba ck into the area forming estua ries, and sands weredeposited in the va lleys a s sea-level rose, a ga in in two tra nsgressive events. Eventua lly the sea completelyflooded a ll of North Dakota and the overlying marine units were deposited.

Inyan Kara sa ndstones deposited in these va lleys are thick, porous (20-30% porosity), and permea ble (Darcylevel) enough to a ccept the injected wa ter a nd the la tera l continuity of the units a llows for injected wa ter tomove into the forma tion (see Cross-Sections A-A' and B-B'), especia lly a long va lley trends. Although somela tera l continuity is importa nt, these units must ha ve good sea ls a bove to protect sha llow aquifers. Theoverlying Creta ceous sha les provide such a sea l a nd, a long with the underlying Swift Formation, a llow forexcellent confining la yers tha t will vertica lly conta in injected brines within the Inya n Kara. The Inya n Kara ispresent only in the subsurfa ce of the W illiston Basin in North Dakota extending a cross most of the sta te. Theformation ranges in thickness from a pproximately 230-440 ft (70-135 m) in the Moha ll 100K.

This map presents thickness contours (isopa chs) of interpreted injecta ble sa ndstone bodies present within theInya n Kara Forma tion in the Moha ll 100K. The map and associated cross-sections w ere prepa red in order toidentify favora ble areas where the potentia l for encountering sa ndstone bodies for injection of produced wateris grea ter. Geographica l fea tures such as roa ds and cities are a lso presented to better a id in well pla cement. Thema p and cross-sections were prepared using wireline logs (gamma ray a nd resistivity) from 834 wells a crossthe Moha ll 100K tha t were a va ila ble for interpreta tion a nd a ssessment of sa ndstone thicknesses and latera lcontinuity. V a lley trends (yellows), oriented to the northwest, ca n be identified on the map. In between theseva lleys in the interfluve area s (darker brown), sandstones are thinner, much less continuous, a nd have lowerporosity and permea bility tha n incised va lley sandstones. Therefore, interfluve sa ndstones are less desira ble forinjection of produced water. R eservoir qua lity ra nges using physica l data (e.g., thickness, gra in size) from ea chwell are presented. H istoric SW D well injection/pressure data from a ctive a nd ina ctive SW D wells are a lsoincluded.

Note: Text modified from Ba der, J.W . and Nesheim T.O ., 2016, Inya n Kara Sa ndstone Isopa ch Map, P a rsha ll 100K Sheet,North Dakota: North Da kota Geologica l Survey, Geologic Investiga tion No. 194.

Control points are included with contour lines and cross-sections to assist the user in evaluating general trends of potentiallyinjectable sandstone bodies. Please note, lateral variability of sandstones can be very great with thickness changes of hundredsof feet in less than 1/2 mile. Therefore, this map should be used only to verify areas of greater sandstone thickness/trends ratherthan absolute values, especially away from control points. Wireline logs in the area should be accessed and evaluated prior tomaking final decisions.

A'

B'A

B

CROSS-SECTIONS

Cross-Section V ertica l Sca le: .75 inches = 200 feet

EXPLANATIONCorrela tion LineCorrela tion Line - InferredCorrela tion Marker H orizonU nconformitySa ndstone Body

Cartographic Compilation: Navin Tha paDrafting: Ken U rla cher

-101°0'

-101°0'

-102°0'

-102°0'49°0' 49°0'

48°30 ' 48°30 '

50

100

150

200

250

350

300

250

150

0

50

INYAN KARA SANDSTONE - ISOPACH INTERVALS (feet)

AVERAGE MONTHLY INJECTION(barrels/one pound per square inch)

") Active SW D W ell: > 150 bbls/psi") Active SW D W ell: 50-150 bbls/psi") Active SW D W ell: < 50 bbls/psi

#* Ina ctive SW D W ell: > 150 bbls/psi#* Ina ctive SW D W ell: 50-150 bbls/psi#* Ina ctive SW D W ell: < 50 bbls/psi

Active Sa lt W ater Disposa l W ellP erfora ted Interva l

P a ved R oa d

£¤2 Federa l H ighw a y

U npa ved R oa d

State H ighw ayUV1804

Other Features

R iver/StreamStream - Intermittent

W a terCity