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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. Stratigraphy. “False Bakken”. Lodgepole Formation. Pelmatozoan limestone.
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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
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 MemberPrairie Salt Prairie Salt ft Contour Interval Montana NorthDakota
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)
StratigraphyBakken Limit in North Dakota South North Mississippian Lodgepole Formation Upper Shale Member Transitional Facies – L5 Upper (Productive) Mississippian Bakken Formation Lithofacies 2 DevonianThree Forks Lower Transitional Facies - L1 Lower Shale Member
StratigraphyCentral Bakken Basin in North Dakota Mississippian Lodgepole Formation South North Upper Shale Member Transitional Facies – L5 Lithofacies 4 Mississippian Bakken Formation Lithofacies 3 Central Basin Facies Lithofacies 2 Transitional Facies - L1 Lower Shale Member Devonian Three Forks
Bottom & Top Seals Devonian Three Forks Fm Mississippian Lodgepole Fm 10562 ft. 10608 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 Canada Antelope Structure Lower Bakken Shale ? ? Montana Heart River Fault ?
FracturingUpper Bakken Shale SWSW Sec. 5, T43N, R99W HF/E M VF/E Montana North Dakota
Balcron Oil - #44-24 VairaSESE Sec. 24, T.24N., R.54E. GR DensityPorosity Lodgepole Fm. 10000 upper Bakken Fm. middle Three Forks Fm. Neutron Porosity
Shell Oil Company - #32-4 Young Bear BIASWNE 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?
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?
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?
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?
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?
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.