Thermal Maturity of the Marcellus Shale and the Line of Death : NE Pennsylvania Conducted by Ethan Shula Department of Science & Mathematics Cedarville University, Cedarville, Ohio eshula@cedarville.edu
Objective: The objective of the study was to identify characteristics of the Marcellus Shale along the Line of Death and determine the principal factors influencing production. Thermal maturity, porosity, clay mineralogy, structural geology, completion procedures play varying roles in the success or failure of unconventional operations. Resolving discrepancies in the location of the Line of Death has the potential for significant economic benefits for operators located in the area.
Study Area Study Area: Susquehanna Co., PA Wyoming Co., PA A total of four wells were included in the study. Chief Oil & Gas LLC : Noble Unit 1H Squier Unit B-2H Harvey Unit 6H Jerauld Unit 1H
Introduction: The Marcellus Shale has developed into the nations most productive unconventional shale play since its emergence in 2004. Drilling efforts have increased exponentially since 2007 and have been primarily located in NE and SW Pennsylvania 8,341 unconventional wells have been completed since 2007 The formation is found within the Appalachian Basin at depths between 4,000 and 9,000 ft. and ranges in thickness from 20 to 250 ft.
EIA Productivity Report Gas production Mmcf/day Region Apr-15 May-15 Bakken 1,549 1,528 Eagle Ford 7,532 7,487 Haynesville 7,118 7,162 Marcellus 16,706 16,716 Niobrara 4,680 4,630 Permian 6,437 6,441 Utica 1,972 2,007 Total 45,994 45,971 Data reported in EIA s April 2015 Drilling Productivity Report.
EIA Productivity Report
Figure 1. Map depicting the depth to the Marcellus Shale (Marcellus Center for Outreach and Research, 2010).
Figure 2. Isopach map of the Marcellus Shale.
Geologic Setting: Line of Death Line of Death (Line of Demarcation) Operators have approximated the location of the line which marks the southern most limit of drilling operations due to the lack of production. Operators point to the region s heightened thermal maturity as the key factor in poor production. High thermal maturation is believed to be the result of extreme thermal and tectonic conditions associated with the Pennsylvania anthracite region to the south. Lackawanna Synclinorium located directly to the southeast
Geologic Setting: Line of Death The Lackawanna Synclinorium is a 110 km long crescent-shaped anthracite basin located in portions of Columbia, Luzerne, Lackawanna, Wayne, and Susquehanna Counties. Anthracite basins threaten natural gas development because of the high thermal conditions necessary for their development and the corresponding degradation of the surrounding strata. Anthracite is the highest rated coal Over 87% carbon content Associated with increased metamorphism
Prepared by Bureau of Topographic and Geologic Survey. Third Edition, Revised, 2000; Third Printing, 2008.
Anthracite Deposition Four Major Anthracite Fields: Northern, Eastern Middle, Western Middle, and Southern Upper Mississippian/Pennsylvanian Strata Coal seems found in the Pottsville and Llewellyn Formations Dominant lithology is sandstone and conglomerate Pottsville includes up to 14 coal beds (many discontinuous) Llewellyn includes up to 40 mineable coal beds Pennsylvanian age strata are time equivalent to the Bituminous fields of Western Pennsylvania
Anthracite Deposition Three Major Orogenic Events: Taconic Orogeny ( 450-500 Ma) Acadian Orogeny ( 360-400 Ma) Allegheny Orogeny ( 230-260 Ma) Allegheny Orogeny (Permian) responsible for the development of the anthracite fields Estimated coalification temperatures: 170 280 o C Estimated geothermal gradients: 33 55 o C/km Estimated burial depths: 4.5 7 km
Anthracite Deposition Hydrothermal Alteration No significant igneous intrusions in close proximity to Lackawanna Synclynorium USGS Open Field Report #92-568 states: orogenic uplift on the eastern flank of the Appalachian basin during the Alleghanian orogeny created a gravity-driven flow system that flushed hot basinal fluids out of the core of the Alleghanian orogen toward the west and northwest Theory that the synclinorium were formed as a result of Upper Silurian Salina salt-collapse structures. Alleghanian fluid or foreland-directed salt migration Resistive sandstone ridges of the synclinal basins protected against erosion of Pottsville and Llewellyn Formations
Previous Work: Thermal maturity values of Devonian strata in the Appalachian Basin have been well documented. Vitrinite Reflectance (%R o ) and Conodont Alteration Indexing (CAI) %R o CAI Vitrinite reflectance is a measurement of the percent light reflectance off the vitrinite maceral at 500x magnification in oil immersion. Conodont alteration indexing utilizes the fossil remains of chordates included in the stratigraphy.
%R o vs CAI Figure 6. Table displaying the conodont alteration index and associated temperatures in comparison with %R values and % fixed carbon (McCarthy et al., 2011).
Figure 4. Correlation of Coal Rank, %Ro, TAI, etc. (Repetski et al., 2008).
%R o vs CAI %Ro vs CAI: Window %Ro CAI Oil 0.5-1.2 1-2 Condensate 1.2-1.8 2-2.5 Dry Gas 1.8-2.5 2.5-4 Overmature >2.5 4-5 Study Area %Ro values: 2.5-3.0 Study Area CAI values: 4.5-5.0 (according to the USGS Professional Paper #1708 by Repetski et. al. 2008)
Figure 4. Devonian %R o(max) isograds of Pennsylvania and New York (Repetski et al., 2008).
Figure 5. Devonian CAI max isograds of Pennsylvania and New York (Repetski et al., 2008).
Clay Diagenesis The concept of shale diagenesis is a significant factor in determining the thermal maturity of the underlying strata. Quantitatively, the most important diagenetic clay reaction in shale is the progressive transformation of smectite into illite via mixed layer illite/smectite (I/S) This reaction is also commonly referred to as smectite diagenesis or smectite illitization, (Pollastro, 1993). Clay mineralogy indicative of thermal maturation
Illite vs %Ro Illite content of Illite-Smectite mixed layer clay minerals*: Ro = 0.5% approximately corresponds to 25% Illite Ro = 0.5-1.0% approximately corresponds to 25-50% Illite Ro 1.5% approximately corresponds to 75% Illite *From Jiang, S., 2012, Clay Minerals from the Perspective of Oil and Gas Exploration: Clay Minerals in Nature Their Characterization, Modification, and Application, Chapter 2. Figure 6. Correlation of Reynolds and Howard s I/S notation and the Hoffman and Hower model (Pollastro, 1993)
Methods: Each well s completion report was reviewed in order to determine the target zones and lithologic sequences encountered. Completion reports were used to determine the perfing records and to help identify specific intervals for sampling. Sample Summary: Sample # Noble Unit 1H 8 Squier Unit B-2H 8 Harvey Unit 6H 10 Jerauld Unit 1H 6
Well Summaries: API # Well County TD TVD Spud Date 37-115-20596 Noble 1H Susquehanna 10,385 ft 7,276 ft 12/16/2011 Formation TD TVD Upper Marcellus 6,886 ft 6,830 ft Purcell 7,086 ft 7,009 ft Hot Marcellus 7,254 ft 7,138 ft Sample Intervals Sample # Interval (TD) Weight (g) #1 9,490-9,520 5.2 #2 9,580-9,610 5.2 #3 9,670-9,700 5.2 #4 9,850-9,880 5.2 #5 9,970-10,000 5.3 #6 10,060-10,090 4.8 #7 10,150-10,180 5.2 #8 10,270-10,300 4.5
API # Well County TD TVD Spud Date 37-115-20614 Squier B-2H Susquehanna 11,992 ft 7,408 ft 11/3/2011 Formation TD TVD Upper Marcellus 7,260 ft 7,215 ft Purcell 7,580 ft 7,392 ft Sample Intervals Sample # Interval (TD) Weight (g) #1 8,080-8,110 5.3 #2 8,590-8,620 5.2 #3 8,950-8,980 5.2 #4 9,550-9,580 5.2 #5 9,970-10,000 3.7 #6 10,480-10,510 4.8 #7 10,990-11,020 5.2 #8 11,800-11,830 5.2
API # Well County TD TVD Spud Date 37-131-20353 Harvey 6H Wyoming 14,640 ft 7,896 ft 11/2/2013 Formation TD TVD Upper Marcellus 7,482 ft 7,395 ft Purcell 7,754 ft 7,608 ft Lower Marcellus 7,850 ft 7,661 ft Hot Marcellus 7,910 ft 7,696 ft Sample Intervals Sample # Interval (TD) Weight (g) #1 8,470-8,500 3.7 #2 9,100-9,200 4.8 #3 9,500-9,600 4.7 #4 10,200-10,300 5.1 #5 10,700-10,800 5.1 #6 11,200-11,300 4.7 #7 11,800-11,900 5.1 #8 12,300-12,400 5.2 #9 12,800-12,900 5.2 #10 13,300-13,400 5.2
API # Well County TD TVD Spud Date 37-115-20562 Jerauld 1H Susquehanna 11,343 ft N/A 7/12/2011 Formation TD TVD Upper Marcellus 7,220 ft N/A Sample Intervals Sample # Interval (TD) Weight (g) #1 10,375-10,400 4.1 #2 10,475-10,500 3.1 #3 10,675-10,700 5.2 #4 10,775-10,800 4.3 #5 10,925-10,950 5.2 #6 11,025-11,050 5.2
Production Trends
Noble 1H Year Month MCF / month 2012 2013 2014 2011-12 76,847 2012-01 64,190 2012-03 19,014 2012-04 18,401 2012-05 38,028 2012-06 36,801 2012-07 68,620 2012-08 68,620 2012-09 66,407 2012-10 68,619 2012-11 66,406 2012-12 68,619 2013-01 193,120 2013-02 174,431 2013-03 193,120 2013-04 186,889 2013-05 193,119 2013-06 186,889 2013-07 156,416 2013-08 156,416 2013-09 151,370 2013-10 156,415 2013-11 151,369 2013-12 156,415 2014-01 127,921 2014-02 115,542 2014-03 127,921 2014-04 123,795 2014-05 127,920 2014-06 123,794 2014-07 94,266 2014-08 94,266 2014-09 91,224 2014-10 94,265 2014-11 91,224 2014-12 94,265 Squier B-2H Year Month MCF / month 2012 2013 2014 2011-11 96,411 2011-12 77,556 2012-07 156,663 2012-08 156,662 2012-09 151,608 2012-10 156,662 2012-11 151,608 2012-12 156,662 2013-01 150,750 2013-02 136,161 2013-03 150,750 2013-04 145,886 2013-05 150,749 2013-06 145,886 2013-07 122,063 2013-08 122,063 2013-09 118,126 2013-10 122,063 2013-11 118,125 2013-12 122,062 2014-01 100,513 2014-02 90,786 2014-03 100,513 2014-04 97,270 2014-05 100,512 2014-06 97,270 2014-07 98,398 2014-08 98,398 2014-09 95,222 2014-10 98,397 2014-11 95,222 2014-12 98,397 Harvey 6H Year Month MCF / month 2014 2013-11 252,588 2013-12 249,539 2014-09 224,938 2014-10 232,436 2014-11 224,938 2014-12 232,435 *Closest proximity to the Line *Initially considered to be to the south of the line
Interpreted Zones of Production Susquehanna Co. Wyoming Co.
Time Mcf/Month 1 77,088 82,806 83,365 94,034 114,557 6 164,037 208,038 200,588 197,838 200,924 196,656 12 202,041 151,222 137,603 150,147 147,421 155,280 18 154,440 91,969 90,243 89,793 91,177 89,793 24 85,734 75,695 75,695 73,253 75,695 73,253 30 75,694 EUR = 12.7 Bcf b = 1.7 Zero-Time Graph: Line Zone Note: EUR evaluation conducted using Halliberton Aries software
Time Mcf/Month 1 234,435 286,341 313,497 293,140 315,453 6 322,519 327,388 306,346 286,222 276,860 268,127 12 262,346 249,027 224,637 234,683 243,855 246,104 18 234,318 183,434 171,017 167,621 172,104 167,568 24 162,335 165,819 157,681 164,334 161,953 164,333 30 183,508 EUR = 24.6 Bcf b = 1.7 Zero Time Graph: Core Zone Note: EUR evaluation conducted using Halliberton Aries software
Methods
X-Ray Diffraction Individual samples were separated, hand ground, packed into micro powder holders, and placed in a goniometer which scanned the samples from 2-60 degrees (2θ). Clay separates, homogenized out of suspension, were placed in a second goniometer and scanned from 2-35 degrees (2θ). Clay separates included only those particle 5μm The same samples were then removed and placed in a container containing glycol vapors. This procedure is performed in order to identify expansive clays (smectite and layered illite/smectite)
X-Ray Diffraction: Results The findings reported by Calgary Rock & Materials Services Inc. were similar between the four sampled wells. Lithologies were comprised of quartz, plagioclase (albite), calcite, dolomite, pyrite, kaolinite, illite, chlorite, and insignificant/minor quantities of layered illite/smectite. The largest Weight % and Vol. Fraction were comprised of Quartz and Carbonate material (calcite/dolomite).
Noble 1H Mineral Mean Wgt. % Carbonate 48.0 Quartz 29.0 Harvey 6H Mineral Mean Wgt. % Carbonate 57.4 Quartz 26.1 Squier B-2H Mineral Mean Wgt. % Carbonate 71.7 Quartz 15.0 Jerald 1-H Mineral Mean Wgt. % Carbonate 33.0 Quartz 32.6 Phyllosilicate composition almost entirely of Illite clays Kaolinite and Chlorite also somewhat persistent
Bulk Sample: Air-dry Run
Clay Separates: Composite-run
Interpretation Peak shifting occurs in samples that contain expansive clays. Two curves are produced, the first (blue) represents the air-dried run, while the second (green) represents the glycolated run. The glycolated samples expand the interlayer distance of the phyllosilicate sheet structure due to the substitution of larger radii glycol molecules for the original H 2 O molecules. Where expansive clay mineralogy is present, the peaks of the blue and green curves will experience shifting.
Spectrum illustrating minor peak shifting occurring at 9θ of Noble Unit 1H #5 sample.
Spectrum illustrating major peak shifting signifying the presence of expansive clay mineralogy.
Photomicroscopy Photomicrograph analysis was conducted using both a Motic 2300 camera mounted on a Motic polarizing microscope and a Nikon Eclipse 50i Polarizing Microscope with NIS Element visual software. Sequential imagery was taken for individual samples and stacked using Helicon Focus Pro imaging software. Images were created from samples located in the treated lateral.
Photomicroscopy: Noble 1H (4x)
Noble 1H (10x)
Squier B-2H (4x)
Squier B-2H (10x)
Harvey 6H (4x)
Jerauld 1H (4x)
Jerauld 1H (10x)
Photomicrograph depiction of cuttings at 4x magnification. A= Squier Unit B-2H; B= Noble 1H; C= Jerauld Unit 1H; D= Harvey Unit 6H.
Conclusion: High carbonate and silicate mineral composition dominate the Lower/Hot Marcellus. Only two samples from the Noble Unit 1H included ordered illite/smectite content. XRD and photomicrograph analyses did not identify any significant differences in the composition of the samples. High % Illite in the clay species separate points to a uniformly mature shale devoid of expansive clays.
Future Consideration: Further evaluation should include: XRD, TOC%, RockEval, SEM Backscatter Imaging, etc. Addition of such data would reveal the type of hydrocarbons present, the quality of the organic matter, the internal pore structure controlling production, and the true thermal maturity of the unit. Significant funding and lab testing required to complete such an undertaking at the undergraduate level.
Acknowledgments: I would like to thank Mr. Terry Ward and Chief Oil & Gas Inc. for providing samples, drilling reports, and all geophysical logs included in the study. I would like to thank Mr. Ray Strom and Calgary Rock and Materials Services Inc. for advising and performing XRD analyses. Additionally, I would like to thank Mr. Keith Mangini and Huntley & Huntley Inc.. Without their help, this project would not have been possible. I would also like to thank Professor Rice and Dr. Whitmore for providing countless hours of work on the development, advisement and completion of the project.
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