JANUARY 2012

The “Better Business” Publication Serving the Exploration / Drilling / Production Industry Improves Bakken Results

By Kevin O’Connell, NPE is drilling and developing two blocks, in Divide, Williams and McKenzie coun- David Skari, aggregating approximately 50,000 net acres ties. Wells are being drilled to target zones Aaron J. Wheeler in the heart of the Bakken Shale in Divide, located between 9,000 and 11,000 feet and Allan Rennie Williams, Dunn and McKenzie counties, true vertical depth. The horizontal pro- N.D. (Figure 1). Led by a highly experienced, ducing sections of the wells average 8,000 DENVER–Developing and technologically focused management team, feet of lateral, which is cased, perforated gas-bearing formations often requires a the company prides itself on customizing its and fractured in multiple stages. The two dense pattern of wells with long lateral drilling and completion methods to the primary intervals targeted within the oil sections. To produce such fields econom- unique geological and geophysical charac- reservoir are a clean dolomite member of ically, producing sections of wells must teristics of its core project blocks. the Three Forks formation and a 15-foot be positioned accurately within the targeted zone below a tight limestone within the Drilling History intervals, while drilling costs are kept to Bakken Middle Member. a minimum. Since early in 2010, Ensign Rigs Nos. Initially, the horizontal production wells A cost-effective solution has been de- 89 and 118 have been working for NPE required drilling a vertical pilot hole that veloped that includes predrill modeling was sidetracked, deviated from vertical of logging-while-drilling measurements FIGURE 1 to build the curve, then drilled laterally along the trajectory of a planned well to North Plains Energy LLC Area of within the producing zone. Wireline logs compare with real-time LWD data. This Operations in North Dakota and cores were run in the initial pilot provides the ability to support geosteering hole to determine the landing point for to and within the target formation. This the sidetrack and to evaluate the optimal geosteering technique has been utilized interval within the reservoir to target. to develop Bakken Shale oil assets. The There was limited regional structural wells have been navigated to land consis- control in planning the laterals. The initial tently in the reservoir, and have successfully well required a sidetrack because it inad- maintained position within the primary vertently drilled into the Upper Bakken target zone for more than 90 percent of Shale. NPE decided that a single geosteered the lateral sections. well trajectory would be more cost effec- North Plains Energy LLC (NPE) is a tive, and the resulting smoother well Denver-based company focused on ac- profile should reduce the risk of losing quiring, developing and enhancing oil the bottomhole assembly. It also would and gas assets within the continental make the completion less problematic. In United States. NPE operates acreage in addition, using LWD tools in the region part of the Williston Basin on the west would provide valuable experience and flank of the Nesson Anticline. A 2008 knowledge about the subsurface geology U.S. Geological Survey assessment of the of the target formations while drilling. undiscovered resources in the Upper De- vonian-Lower Mississippian Bakken for- Geosteering Partnership mation of the Williston Basin Province in Prior to geological steering methods, Montana and North Dakota estimated the success of a oper- mean undiscovered volumes of 3.65 billion ation depended largely on steering the barrels of oil, 1.85 trillion cubic feet of well through a target reservoir with an associated , and 148 million assumed position fixed in geometric space. barrels of natural gas liquids. However, a success in geometric terms

Reproduced for with permission from The American Oil & Gas Reporter www.aogr.com Oil & Gas Shales

could be a failure in economic terms if were utilized to calculate the expected urements. Because these measurements the assumed and actual geometric locations LWD response of formations into which were similar to wireline resistivity meas - of the reservoir differed. horizontal wells were to be drilled. LWD urements, the LWD logs were correlated Effective well placement in horizontal data types typically modeled included with similar wireline logs to locate im - drilling requires that geological changes gamma ray, resistivity, density-neutron portant geological features. Because the be detected quickly, and that the well (imaging), and sonic measurements. wave propagation measurements were plan be adjusted in a timely fashion. With The objective of geological steering well characterized, the LWD log response this challenge in mind, a dependable ge - depends on the section of the well. In the was predictable under most conditions ological steering partnership was developed build section, where the deviation increases observed. between NPE and PathFinder, a Schlum - from the kickoff point until the well enters The LWD resistivity tools have multiple berger company, for providing directional the reservoir, the goal is to steer the well transmitter-receiver spacings and multiple drilling and MWD/LWD services, sup - so that it enters the reservoir at a desired frequencies. The resistivity measurement ported by the company’s PayZone Steer - inclination and direction. In the lateral from each spacing and frequency responds ing™ services at the well site. The real- section, the goal is to position the well’s differently to a resistivity interface located time forward modeling software assists path to optimize well bore exposure to away from the well bore. Since the nature in geologically steering deviated well tra - the reservoir. of the resistivity interface is known from jectories by combining petrophysical data These goals have been achieved con - the offset well logs, multiple resistivities from LWD logs run in offset wells, the sistently through interpreting real-time can be leveraged to obtain a profile to geological earth model, and the directional LWD measurements, gamma ray in the help maintain the well’s position within well plan to create a model of the forma - build section, and gamma ray combined the target interval at a distance from the tions being drilled. with resistivity in the lateral section. These interface. During the early stages of the project, LWD measurements were selected by During drilling, an experienced service company staff, working in close evaluating the log response characteristics geosteering field engineer compared the consultation with the operator’s technical within and adjacent to selected target measured LWD responses with the mod - team, focused on learning the geologic zones of the Bakken Middle Member and eled synthetic responses to determine the setting in the area. Effective communica - Three Forks formations. position of the well’s path within the ge - tions among the team allowed it to as - ological sequence. The engineer also ref - semble local earth models based on avail - LWD Resistivity erenced all other relevant information, able seismic data, structural information, Electromagnetic wave propagation re - such as cuttings sample observations from and information from selected offset wells. sistivity tools delivered the standard deep- the geologist, to support the geosteering interpretation. Wireline and LWD data from offset wells sensing LWD array wave resistivity meas - The resulting geologic interpretation, which incorporated observed differences FIGURE 2 between expected and measured LWD Prewell Model of the Projected Landing Point (Holland No. 9-19H) responses, combined with additional drilling-related data, was communicated GAPI CHMM CHMM 1,000 RT_RHTE to NPE to allow the drilling and geology RSPH_M 9,690 RMPH_M team to make time-critical decisions effi - 100 RDPH_M y t i

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t ciently about adhering to or modifying s i s e R

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e the well plan. l

Upper Bakken e d o M The team was able to adjust the drilling 1 Modeled Resistivity Response 9,720 plan as the horizontal well was drilled,

GAPI ORR_S using actual well bore trajectory data and

120 LWD logging measurements. In consul - P

O tation with NPE, the team incorporated R / y a 80 R

9,750 a interpretations to reconcile the local geo - m m a G logic model with real-time data, allowing D

V 40 R Modeled Gamma Ray Response the well bore position to be maintained

0 within the target zone. feet 9,690 9,780 Lower Bakken Refining Results

9,720 Planned Well Trajectory Real-time LWD data acquired from

9,750 Projected landing point within the zone of interest not only were D V

T at 9,806 feet TVD based 9,810 correlated with the synthetic model, but on initial geologic model 9,780 Three Forks target interval also were back-correlated with previous identified by red lines and well plan measured data from the same well as the 9,810 trajectory moved upstructure or down - structure within the target formation. All feet 0 40 80 120 1 10 100 1,000 9,760 9,840 9,920 10,000 10,080 Gamma Ray Resistivity decisions regarding changes to the well Oil & Gas Shales

FIGURE 3 trajectory considered BHA capabilities, Geologic Interpretation Displaying the Well Bore Position the original directional well plan, and Within the Three Forks Formation Target Interval completion requirements in consultation with NPE. Continuous control of the well

API OHMM OHMM 1,000 RT_RHTE bore trajectory delivered reduced tortuosity Vertical Depth Correlation RSPH_A y t i v i t

1s 00 and dogleg severity, leading to quicker i RMPH_A s e R

RDPH_A e

m well bore completion and production. i 10 RDAL_A 9,740 T - l a e

Upper Bakken R LWD data and forward modeling in - 1 Real-Time Resistivity Measurements terpretation results were delivered at the OHMM 1,000 Modeled Resistivity Response RT_RHTE well site and remotely, using secure Web- RSPH_M y t i

1v 00 i RMPH_M t based applications. This enabled real- 9,760 s i s

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l 10 RDAL_M time collaboration from directional drillers, e d o M geologists, and other experts in multiple 1 locations. A final post-well analysis depicts GRC_A 9,780 ROP_A log evaluations and further refinement of 150 P

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y the local model to obtain the best fit, re -

a GRR_S R

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m GRCA_A R sulting in a close-modeled approximation m a G 50 of the actual measured formation prop - 9,800 Real-Time Gamma Ray (Green) versus Modeled Gamma Ray & ROP 0 feet erties.

9,720 The enhanced model was incorporated Lower Bakken Well Bore Trajectory into the plan for the next well, delivering 9,740 an increasingly refined result. Observations 9,820 of the results are compiled and documented 9,760 D

V for use as a future frame of reference to T Three Forks target interval 9,780 identified by red lines further optimize drilling procedures.

9,840 Directional drilling, measurement- and 9,800 logging-while-drilling (M/LWD), and for - Landing Pl.

9,820 ward-modeling steering services, combined Real-Time PZS Structural Interpretation with the extensive experience of the NPE 0 50 100 150 1 10 100 1,000 10,000 11,000 12,000 13,000 14,000 15,000 16,000 17,000 feet Gamma Ray Real-Time Resistivity MD drilling team, have enabled consistent po - sitioning of the horizontal wells in zone. Success in this geological well positioning FIGURE 4 partnership has been achieved through close teamwork and timely communica - Correlation Displaying Character Difference tions, while continually building on the Between Top and Base of Three Forks Target Formation knowledge gained from each well to ac -

API OHMM OHMM cumulate an ever-increasing understanding 1,000 RT_RHTE y t i RSPH_A

Vertical Depth Correlation v i 9,840 t s of subsurface conditions and the optimal 1i 00 RMPH_A s e R

RDPH_A e

m drilling parameters required to effectively i 10 RDAL_A T - l a e

R and efficiently conclude the geologic in - 1 Real-Time Resistivity Measurements 9,842 OHMM terpretation. 1,000 RT_RHTE RSPH_M y t i v i 1t 00 RMPH_M s i s

e RDPH_M Geosteering Support R

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9,844 e d o

M Since July 2010, the PZS service has 1 Modeled Resistivity Response

API been used to support geosteering new pro - GRC_A ROP_A

1P 50 duction wells on NPE’s acreage in Divide,

9,846 O

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1 00 D Williams and McKenzie counties. The a V m R GRCA_A m a

G 50 software has provided a platform for in - Real-Time Gamma Ray (Green) versus Modeled Gamma Ray & ROP 9,848 0 terpreting log response to characterize key feet 9,745 horizons in each well, typically focusing Real-Time PZS Structural Interpretation 9,750 on either the Middle Member or Three

9,850 9,755 Forks and their adjacent formations. Well Bore Trajectory

9,760 The service has leveraged and utilized D V T 9,765 the diverse experience of all members of 9,852 9,770 a multidisciplinary team, including NPE

9,775 drilling engineers and geologists, the rig Three Forks target interval 9,780 identified by red lines crew, mud logger, well site geologist, di - 9,854

0 50 100 150 1 10 100 1,000 13,800 14,000 14,200 14,400 14,600 14,800 15,000 15,200 15,400 16,600 feet rectional drillers, M/LWD geological steer - Gamma Ray Real-Time Resistivity MD ing field engineers, expert log analysts, and off-site geosteering operations per - feet deeper). gamma ray, resistivity, and directional sonnel. A communication workflow was Seven-inch casing was set to 10,202 data, combined with geological in formation established that has met the challenges of feet, then the lateral producing section from mud logging, to advise NPE on delivering efficient decision protocols while was drilled using a 6-inch PDC bit, 1.5- steering the well within the planned ob - involving all members of this diverse team. degree adjustable steerable G2 mud motor, jective, following the dip of the formation 3 Between August 2010 and August slim (4 ⁄4 inches) advanced wave propa - (Figure 3). 2011, the PZS service was used to consult gation resistivity and The inclination of the lateral ranged on 17 wells on NPE’s acreage. In these tool, and an MWD positive pulse telemetry between 89 and 93 degrees, reacting to wells, approximately 130,000 feet of system. While drilling the lateral, the the regional dip changes. Accurate well lateral section were drilled after entering geosteering field engineer used real-time positioning was achieved by characterizing the primary target zone(s), and 120,000 feet (92 percent) of those lateral sections FIGURE 5A were positioned within the primary target Real-Time Structural Interpretation Conducted at the Well Site zone(s). (Middle Bakken Formation) Holland No. 9-19H API OHMM OHMM RT_RHTE y t i

v RSPH_A i Vertical Depth Correlation t s

i 10 The Holland No. 9-19H well, drilled s RMPH_A e R RDPH_A 10,860 e m i during January-February 2011, is typical T RDAL_A - l a e R of wells drilled for NPE leveraging the Real-Time Resistivity Measurements OHMM forward-modeling geosteering technology. Modeled Resistivity Response RT_RHTE y t

i RSPH_M v i

10,890 1t 00 s

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Prior to drilling, local geological models s e

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d e l were constructed based on log data from e d o five offset wells, including one of the M 10,920 pilot wells drilled early in the project, GRC_S 120 SLBD_A

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Bank of St. Paul. The geological objective G R of the new well was to land and maintain 10,950 30 Real-Time Gamma Ray (Green) versus Modeled Gamma Ray & ROP 0 10,840 position within the dolomitic section of feet ActualW ActualW the Three Forks formation. 10,880 The regional structural map of the 10,980 Upper Bakken Upper Bakken Shale top horizon predicted 10,920 Middle Member target D

V Well Bore Trajectory the target zone would have an upward T interval identified by red lines apparent dip of 0.6 degrees in the direction 11,010 10,960 proposed for the lateral. The drilling team 11,000 was made aware of the initial drilling Landing Pl. Real-Time PZS Structural Interpretation 11,040 plan and possible alternate scenarios, Lower Bakken 11,040 0 30 60 90 120 1 10 100 11,000 12,000 13,000 14,000 15,000 16,000 17,000 18,000 19,000 feet along with their inherent uncertainties. Gamma Ray Resistivity MD Figure 2 displays the prewell geologic model with the anticipated logging response along the proposed well path. FIGURE 5B After drilling vertically to 8,300 feet Correlation Displaying LWD Measurements Character total depth, the PZS service was initiated As Utilized for Geosteering Decisions to complement geological and mud logging API OHMM OHMM Upper Bakken RT_RHTE

y RMPH_A information for picking the kickoff point. t i v

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11,000 s e RDAL_A Building the curve started at 9,280 feet, R

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m RSPH_A i T - l using a 2.5-degree bend, PathFinder G2 a e 3 3 R Real-Time Resistivity Measurements 4 4 mud motor, an 8 ⁄ -inch PDC bit, and 6 ⁄ - OHMM 11,005 RT_RHTE

y RSPH_M t i v inch gamma ray logging and directional 1i 00 t RMPH_M s i s

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tools. The real-time geosteering technology d e l e

11,010 d o was managed by an experienced field en - M Modeled Resistivity Response gineer on site. Prewell modeling, remote GRC_S 120 SLBD_A support during operations, and post-well y GRCA_A 11,015 a

R 90

a ROP_A m analysis were performed in Lafayette, La. m 60 a D G V Formation changes were logged and R 30 Real-Time Gamma Ray (Green) versus Modeled Gamma Ray & ROP

11,020 0 10,970 observed differences to the original model feet ActualW ActualW Middle Member target were used to compute adjustments to 10,960 interval identified by red lines revise the landing point. At an angle close 11,025 to horizontal, the well successfully entered 10,990 the target zone at 9,805 feet TVD (10,096 11,000 D V T 11,030 feet TD) to reach the 9,808-foot TVD re - 11,010 Well Bore Trajectory vised landing point, 2.5 feet below the 11,020 top of the target clean dolomite within 11,035 Real-Time PZS Structural Interpretation the Three Forks formation. This compares Lower Bakken 11,030 Vertical Depth Correlation 11,040 with a planned landing point based on 0 30 60 90 120 1 10 100 13,000 13,500 14,000 14,500 15,000 15,500 16,000 feet the initial model at 9,815 feet TVD (seven Gamma Ray Resistivity MD Oil & Gas Shales

measured gamma ray and resistivity re - efficiency directional drilling programs excellent service. Maintaining consistency sponse differences between the top and for Bakken Shale oil targets in NPE’s of the team, particularly the on-site per - the base of the Three Forks formation North Dakota acreage. Offset well data sonnel, is valuable in building and retaining target interval. and other information provided input to knowledge and experience to continuously At the top of the target interval, the re - generate geologic models and synthetic improve the well-placement process, and sistivity is higher with more separation, in LWD responses of the planned well bore. to improve operational efficiency. combination with slightly lower gamma Real-time LWD measurements and In this example, for the 17 laterals ray measurements at the top versus the downhole samples have enabled a dedi - drilled between August 2010 and August base (Figure 4). Well total depth was cated, experienced team to accurately steer 2011, the partnership between the operator achieved at 17,739 feet MD, 9, 725 feet the wells to the required target zone and and service provider contributed to an TVD. Of the 7,643 feet of lateral footage drill the lateral sections, maintaining the average of 92 percent of the well bore drilled, 7,214 feet (94.4 percent) of the well position within the target formations. length being successfully positioned within well bore was positioned within the target Reliable reporting and effective lines the targeted intervals of the Bakken Middle interval. of communication among the multidisci - Member and Three Forks formations. r plinary team of on- and off-site, office- Lessons Learned based personnel are essential to providing The LWD log responses observed for the wells targeting the Bakken Middle Member were characterized in a similar KEVIN O’CONNELL is manager of agement, and a Ph.D. from Walden fashion as the Three Forks wells. The 15- operations at North Plains Exploration University. foot thick target interval below the tight with 29 years of experience in production, limestone maintains consistent, nondescript completions and drilling operations. AARON J. WHEELER is the PayZone gamma ray and resistivity characteristics His areas of work include most major steering adviser and geosteering oper - below the limestone, continuing down to basins in the lower-48 and Alaska, with ations manager for PathFinder, a the lower Bakken Shale. experience ranging from coalbed Schlumberger company. He has more The lack of character through the lower methane to deep drilling and completions, than 15 years’ experience working with half of the Middle Member formation along with horizontal well activities. MWD/LWD services for formation eval - presents a challenging interpretation. Before joining NPE, O’Connell served uation, geosteering and pore pressure Therefore, the cleaner gamma ray and as the operations manager for GMT evaluation. Wheeler received his B.S. slightly higher resistivity of the limestone Exploration Company. He has a B.S. in in civil engineering from Texas Tech directly above the target interval are engineering from the Uni - University. He is a member of the utilized as benchmarks to solidify the versity of Wyoming and is a registered Society of Petrophysicists and Well Log geosteering interpretation. professional engineer in Colorado. Analysts, and the Society of Petroleum The resistivity measurements begin to Engineers. separate and increase according to their DAVID SKARI is a geologist with respective diameters of investigation as North Plains Energy. He has 26 years ALLAN RENNIE is a business de - the well bore approaches the contrast in of experience in the . velopment manager and M/LWD product resistivity between the target interval and Prior to joining NPE, he was an area champion for PathFinder, a Schlum - tight limestone ceiling. Maintaining well and district manager for Smith Tech - berger company. He has been working bore inclination near to formation dip al - nologies, managing operations around for more than 20 years in technology and operations, developing and sup - lows the well bore position to be confirmed the world, including West Africa, the Middle East, the Far East and Russia. porting a wide range of M/LWD systems without drilling into the limestone (Figures Skari holds a bachelor’s in geology and services for well placement, for - 5A and 5B). from the University of Colorado at mation evaluation, geosteering, and Utilizing LWD measurements to ac - Boulder, an M.B.A. from the American downhole ranging (passive/active) ap - tively geosteer in real time is a cost- Graduate School of International Man - plications. effective way to support high-volume/high-