Julie A. LeFever North Dakota Geological Survey Horizontal Drilling Potential of the Middle Member Bakken Formation, North Dakota Julie A. LeFever North Dakota Geological Survey

Williston Basin AB SK MB ND MT SD WY North Dakota Study Area

Pelmatozoan limestone Stratigraphy “False Bakken” Lodgepole Formation Pelmatozoan limestone Mississippian upper Bakken Formation middle lower Devonian “Sanish” Three Forks Formation

Isopach Map of the Middle Bakken Member Contour Interval: 5 ft

Bakken Middle Member Prairie Salt ft Contour Interval Montana North Dakota

Lithofacies of the Middle Member Upper Shale Lithofacies 5 - Siltstone Lithofacies 4 – Interbedded Dark Grey Shale and Buff Silty Sandstone Lithofacies 3 - Sandstone Productive Lithofacies 2 – Interbedded Dark Grey Shale and Buff Silty Sandstone Productive Lithofacies 1 - Siltstone Lower Shale (From LeFever and others, 1991)

Stratigraphy Bakken Limit in North Dakota South North Mississippian Lodgepole Formation Upper Shale Member Transitional Facies – L5 Upper (Productive) Bakken Formation Mississippian Lithofacies 2 Devonian Three Forks Lower Transitional Facies - L1 Lower Shale Member

Stratigraphy Central Bakken Basin in North Dakota Mississippian Lodgepole Formation South North Upper Shale Member Transitional Facies – L5 Lithofacies 4 Bakken Formation Mississippian Lithofacies 3 Central Basin Facies Lithofacies 2 Transitional Facies - L1 Lower Shale Member Devonian Three Forks

Devonian Three Forks Fm Mississippian Lodgepole Fm Bottom & Top Seals Devonian Three Forks Fm Mississippian Lodgepole Fm 10608 ft. 10562 ft. 10564 ft. SESW Sec. 13, T.23N.,R.56E.

Lower Bakken Shale Member Contour Interval: 5 ft NESE Sec. 27, T150N., R97W

Upper Bakken Shale Member Contour Interval: 5 ft NESE Sec. 27, T150N., R97W

Middle Member Bakken Porosity Matrix porosity Primary Secondary Fracture porosity Related to Tectonics Regional Salt tectonics Related to HC Generation

Regional Fractures Lower Bakken Shale Heart River Fault Canada ? ? ? Antelope Structure Lower Bakken Shale ? ? Montana An example of how basement features has possibly affected the overlying rocks can be seen on this diagram. The Heart River Fault that defines the Richardton-Taylor fields displaces basement rocks. The fault falls on trend with an easily mappable trend apparent in the lower Bakken shale. The mappable trend is present due to fluid movement along the fault resulting in the dissolution and subsequent collapse of the overlying rocks at the time the shale deposition. Subsequent dissolution and collapse can easily result in repeated episodes of fracturing throughout the overlying section. This can also be related to additional changes in depositional environments, distribution and thicknesses of facies present. Heart River Fault ?

Fracturing Upper Bakken Shale SWSW Sec. 5, T43N, R99W HF/E M VF/E Examination of the cores of the Bakken shale through North Dakota reveals that in areas of intense hydrocarbon generation, the common fracture pattern within the shales is vertical. As the rocks become more immature, fracturing changes from a vertical orientation to a horizontal orientation and ultimately to a non-fracture, massive shale. Montana North Dakota

Balcron Oil - #44-24 Vaira SESE Sec. 24, T.24N., R.54E. GR Density Porosity Lodgepole Fm. 10000 upper Bakken Fm. middle Three Forks Fm. Neutron Porosity

Shell Oil Company - #32-4 Young Bear BIA SWNE Sec. 4, T148N, R92W GR GR Den L3 L2 Bakken Formation

Conoco, Inc. - #17 Watterud “A” SENW Sec. 11, T160N, R95W GR Res Lithofacies 3 Central Basin Facies Upper L2 Facies

Bakken Formation Highly overpressured – 5500 to 5800 psi Migration Bakken Source System Hydrocarbon Generation High volumes – 200 to 413 billion bbls (ND + MT) Bulk volume change in the rock Formation of micro- and macro- fractures Common in zones with higher organic content Producers High Gravity Oil – 39 to 46o API No water

Differences – MT to ND ND bottom hole temperature is higher ND is clastic versus carbonate ND bottom hole pressure is higher (.50-.58 psi/ft) Bakken shale open hole is not stable Rock properties Naturally fractured Oil wet Swelling and migrating clays

Non-confidential Drilling Results to Date Ten (10) wells total Single lateral - Open hole re-entry (1) Re-Entry – Open hole – Lodgepole liner uncemented (1) Dual lateral – Open hole or perforated liners – Lodgepole liner uncemented (4) Proppant fractured (3), Unstimulated (1) Single lateral - Perforated liner (4) Dual lateral - Co-planar – Perforated liners (0)

Results Single lateral - Open hole re-entry (1) IP 332 BO / 34 BW / 95 MCFD (Cum BO – 25,000) Marginally successful 1st Attempt Hole stability problems in the upper shale? Proppant fracture growth into Lodgepole? Single lateral - Open hole re-entry (1) IP 332 BO / 34 BW / 95 MCFD Proppant Fractured almost immediately 87 BO / 146 BW / 150 MCFD Current 43 BO / 10 BW / 89 MCFD 25,000 cumulative BO; Breakeven at $22/BO Problems and Questions 1st ND attempt – marginally successful Hole stability in upper shale? Proppant fracture growth into Lodgepole?

Results Re-Entry – Open hole – Lodgepole liner uncemented IP 263 BO / 0 BW / 177 MCFD (Cum BO – 23,000) Proppant Fractured after 4 months and 19,000 BO 304 BO / 0 BW / 172 MCFD Current 304 BO / 0 BW / 172 MCFD Successful! Liner maintained hole stability? Liner hanger packer kept proppant fracture in zone? Pressure drawdown kept proppant fracture in zone? Re-Entry – Open hole – Lodgepole liner uncemented IP 263 BO / 0 BW / 177 MCFD Proppant Fractured after 4 months and 19,000 BO 304 BO / 0 BW / 172 MCFD Current 304 BO / 0 BW / 172 MCFD 23,000 cumulative BO Problems and Questions This worked! Liner maintained hole stability? Liner hanger packer kept proppant fracture in zone? Pressure drawdown kept proppant fracture in zone? Good rock?

Results Dual lateral – Open hole or perforated liners – Lodgepole liner uncemented IP 51 BO / 171 BW / 44 MCFD (Cum BO – 11,000) Proppant Fractured immediately to after 1 month 134 BO / 179 BW / 125 MCFD Current 32 BO / 37 BW / 72 MCFD Not successful! Liner maintains hole stability? Proppant fracture growth into Lodgepole or higher zones? More pressure drawdown to keep prop fracture in zone? Dual lateral - OH or perforated liners – Lodgepole liner uncemented IP 51 BO / 171 BW / 44 MCFD Proppant Fractured immediately to after 1 month 134 BO / 179 BW / 125 MCFD Current 32 BO / 37 BW / 72 MCFD 11,000 cumulative BO Breakeven at $45/BO Problems and Questions This has not worked! Liner maintains hole stability? Proppant fracture growth into Lodgepole? One well has water salinity and H2S indicative of Mission Canyon 2 wells have isolated the lateral the uncemented through the Lodgepole leg (what to do with spacing?) Only the best rock and more pressure drawdown to keep prop fracture in zone?

Results Dual lateral – Open hole or perforated liners – Lodgepole liner uncemented IP 463 BO / 12 BW / 512 MCFD (Cum BO – 22,000) Not proppant fractured yet Current 172 BO / 0 BW / 166 MCFD Fairly Successful! Liners maintaining hole stability? Complicated mechanically? Pressure drawdown may keep proppant fracture in zone? Mechanical problems may prevent proppant fracturing? Dual lateral - OH or perforated liners – Lodgepole liner uncemented IP 463 BO / 12 BW / 512 MCFD Not proppant fractured yet (planned to wait – MECHANICAL) Current 172 BO / 0 BW / 166 MCFD 22,000 cumulative BO Breakeven at $18/BO Problems and Questions This worked (sort of) Liners maintaining hole stability? Complicated mechanically? Good rock? Pressure drawdown may keep proppant fracture in zone? Mechanical problems may prevent proppant fracturing?

Results Single lateral - perforated liner – Lodgepole cemented IP 275 BO / 107 BW / 264 MCFD (Cum 12,000 BO) Proppant Fractured immediately to after 3 months 179 BO / 110 BW / 183 MCFD Current 83 BO / 20 BW / 126 MCFD Fairly Successful! Casing maintains hole and stops fracture growth into Lodgepole? Mechanically simple? More pressure drawdown to improve keep proppant fracture in zone? Single lateral - perforated liner – Lodgepole cemented IP 275 BO / 107 BW / 264 MCFD Proppant Fractured immediately to after 3 months 179 BO / 110 BW / 183 MCFD Current 83 BO / 20 BW / 126 MCFD 12,000 cumulative BO Breakeven at $25/BO Problems and Questions This has worked (fairly well) Casing maintains hole and stops fracture growth into Lodgepole? Mechanically simple? Good rock? More pressure drawdown to improve keep proppant fracture in zone?

Conclusions The Lithofacies are present basinwide. Primary reservoir porosity may be enhanced by diagenesis, tectonic fractures, and/or fractures from HC generation. Porosity enhancement is not restricted to a single lithofacies within the Middle Member. Type of fluid used while drilling may have adverse effects on production. The presence of vertical fractures in areas of intense HC generation may affect the outcome of stimulation treatment.

Conclusions Production prior to fracture stimulation treatment may increase the potential of staying in zone Additional fracture stimulation treatments may increase reserves.