Shale Shaker Vol 70, No 4 July- August

$15.00 U.S.


The Discovery and Geology of the Potato Hills Gas Field Favorite Thin Section: Caney Sandstone from Philip’s Creek Favorite Outcrop: The Great Dakota Sandstone Wall

And Much More.

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The Journal of the Oklahoma City Geological Society Volume 70 Number 4

The Shale Shaker The Shale Shaker is published under the oversight of members of the OCGS Publications Committee, who are responsible for all of the editorial and technical content. Publication production assistance provided by: ART DIRECTOR, PRODUCTION AND DESIGN Theresa Andrews, Visual Concepts and Design, Inc. OCGS Board Officers President – Stephen Ladner Vice President /Membership Chair – Patrick Kamann Secretary – Cole Hinds Treasurer & Finance Committee Chair – Drew Dressler Councilor & Governance Chair – Herb Martin Social Committee Chair – Galen Miller Education Committee Chair – Rosie Gilbert Website Chair – Julian Michaels Shale Shaker Editor/Publications Chair – Dan Costello

Directors Doug Bellis Lesley Evans Eric Kvale Britni Watson Mallory Zelawski OCGS OFFICES 10 NW 6th St. Oklahoma City, OK 73102 Phone: (405) 235-3648 | Fax: (405) 235-1766 Website:

AAPG Mid-Continent Section Representative H.W. (Dub) Peace, Geologist and AAPG Mid-Continent Section Past President Past President – John Brett

July ~ August 2019 | Page 147

The Journal of the Oklahoma City Geological Society Table of Contents

Shale Shaker Features

150 Coming Attractions ; Steve Ladner, President, OCGS Board of Directors

182 My Favorite Outcrop: The Great Dakota Sandstone Wall, The Day The Earth Shook, White Smokers, The Colorado National Monument, And Viniculture On The Western

151 Letter from the Editor: Staying Balanced; Dan Costello, Editor

Slope: A Colorado Journey ; S.J. Mazzullo, Geological Consultant and Professor Emeritus, Wichita State University; Chellie S. Mazzullo, Petroleum Geologist, Wichita, KS


Upcoming Events


OCGS Membership & New Members

191 Announcement: OCGS 27th Annual Shrimp Boil


What You Missed: 2019 Golf Tournament

156 The Discovery and Geology of the Potato Hills Gas Field, Latimer and Pushmataha Counties, Oklahoma; P. Paul Denney, Independent Geologist, Colorado Springs, CO 168 My Favorite.....Thin Section: The Caney Sandstone from Philip’s Creak-One of Rick Andrews’ Favorite Outcrops; Andrew Cullen, Warwick Energy

192 State of the Industry; Dan Costello


Advertisers Index

About the Cover

Theresa Andrews created the cover of the Shale Shaker. COVER PHOTO: The cover photo is a chromite-bearing harzburgite from the Dun Mountains in New Zealand, type location for Dunite - an ultramafic rock with >90% olivine. The high relief, strongly birefringent, grains are forsterite olivine crystals (Mg0.9Fe0.1)SiO4) encased by poikilitic orthopyroxene (enstatite). The opaque octahedral chromite grains (MgFe) Cr2O4) impart a chiaroscuro effect to this microscopic canvas. Chromite deposits are often associated with layered ultramafic complexes, Stillwater Complex, Montana;

Bushveld Complex, South Africa. In southwest Oklahoma, the Cambrian-age Glenn Mountain igneous suite has layered ultramafic rocks, such as troctolite and anorthosite. Anaconda Minerals conducted a limited exploration program appraising the platinum potential of the Glenn Mountain complex. Minor platinum anomalies were found in rock and sediment samples, but they were deemed insufficient to warrant further appraisal (see Cooper pages 65-72 in OGS Guidebook 23, 1986).

Page 148 | Volume 70 Number 4

ISSN: 0037-3257 Shale Shaker is the registered trademark of the Journal of the Oklahoma City Geological Society. The Shale Shaker (USPS 000- 771) is published bi-monthly from January through December by the Oklahoma City Geological Society, 10 NW 6th Street, Okla- homa City, OK 73102. Annual membership dues for the Oklahoma City Geological Society are $100.00 and a subscription to the Shale Shaker is included with each membership. For non-members, the subscription rate is $60.00 in the U.S.A. and $80.00 for- eign per year. Layout and typesetting by Theresa Andrews, Visual Concepts and Design Inc., Oklahoma City. Send email address changes to: Shale Shaker , 10 NW 6 th Street, Oklahoma City, OK 73102 or All materials herein are copyrighted by the Oklahoma City Geological Society. The purpose of the Shale Shaker is two-fold: To keep members informed of the activities of the Society and to encourage the ex- change and dissemination of technical information related to the geological profession. The Shale Shaker welcomes contributions from all sources, but does not intend to adopt any position nor endorse any specific policies through this publication; instead, it endeavors to provide a neutral forum for exchange of ideas and technical discussions amongst professionals serving the geosci- ences. It is committed to serve the geoscience community with scientific, technical and other related information, so to encourage professional development while not endorsing specific policies. DISCLOSURE AND DISCLAIMER: The views, comments, and opinions expressed in the articles and columns of the Shale Shaker are those of the respective authors and not necessarily those of the OCGS or the staff of the Shale Shaker . Neither the OCGS, nor the staff of the Shale Shaker , make any representation as to the accuracy or correctness of the material presented within the Shale Shaker .

July ~ August 2019 | Page 149

Letter from the OCGS President

By: Steve Ladner, President, OCGS Board of Directors

Coming Attractions

ing a Mudrocks Seminar, also on Oct 1, OCGS will be hosting an  Open House for its members,  come by and have a drink; It’s a good time to visit and meet some old friends and make some new friends. We will also be sponsoring another Mentoring Opportunity, “Stump the Chump”. We will have a panel of experts open to all sorts of questions from geology to man- agement.   November will bring our fall clay shoot on November 8, and a field trip to the Ar- buckles. Fall brings so many great events including OCGS events, please sign up and be a part of the society, meet some new people and have some fun.

With the August heat, comes the hope for fall with cooler weather, football, and the seasonal changes.  Fall also brings another season for OCGS events.  The OCGS will be resuming their programs in September. The Annual Shrimp Boil will be the first Friday in September,   along with our first luncheon on Wednesday, September 25. There will be a core workshop on Sep- tember 17 at Chesapeake  We will also be holding mock interviews for OU students on Sept 4,  if you would like to volunteer please feel free to contact us. October brings Jeff May  on  Oct 1-2 do-

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Page 150 | Volume 70 Number 4

Letter from the Editor

By: Dan Costello, Editor

ingly with other teams. The Land team remains as important as ever – even if you have a great prospect, you can’t start on it until you have drilling rights. The promi- nence of data science teams has risen in many organizations, and we have a wealth of data in geoscience that these teams can help for managing and utilizing. As capi- tal efficiency becomes more important, we need to work closer with finance and accounting to ensure our data acquisition is focused and appropriate business-wise. The other side of the “integration” coin is not losing our geoscience skills. In re- cent years, especially in horizontal plays, many of the breakthroughs have come on the engineering side such as maximizing or optimizing completions. As we move many resource plays to development drill- ing, we have a much greater density of production data points relative to well log control points. It can be difficult to keep geology relevant at this phase of a field, but it is our job to ensure we don’t forget about the rock. So how best to manage the move towards integration – learning more about the oth- er aspects of the industry while not letting up on the geology side? A good place to start is by spending time with our counter- parts’ on the job, learning what their con- cerns are and understanding what drives their decisions. These sessions can easily

lead to breakthroughs as to how our geo- logic knowledge of a field can impact their operations, and vice-versa. The local SPE chapter has monthly luncheons and occa- sional continuing education opportunities. Similarly, there are many ways to keep our geologic skills sharp. Perhaps you’ve heard the saying, “Whoever sees the most rocks wins”. The same is true for well logs, geochemical data, thin sections, etc. Every exposure to the subject adds to our inter- nal database for future projects. When I’ve been working on the same field/formation for months/years, I’ve found it useful to take a break and map a nearby play. Try- ing to understand what drives production there can provide insight to other projects. In the wider scheme of development and growth, there are continuing educa- tion classes available. While in the past many of these courses required travel to Houston, we at the OCGS have doubled- down on education and now aim to pro- vide 6-8 short courses a year. I have been impressed how much the instructors of these classes have worked with us to build a comprehensive curriculum and keep prices manageable. Be on the lookup for upcoming announcements for classes on topics ranging from core workshops to petrophysics to risk assessment.

Dan Costello

Staying Balanced One of the common buzzwords in the oil and gas industry (and maybe all indus- tries) has been integration . We hear calls for “breaking down silos” and “seamless communication” between teams. This is an obvious good idea, but comes with a handful of challenges. The first potential issue can understanding the details of other disciplines outside ge- ology, which we typically did not study as much in school. In most companies, ge- ologists are expected to collaborate with varying engineers – drilling, completions, production, and reservoir – and increas-

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July ~ August 2019 | Page 151

OCGS Events






Page 152 | Volume 70 Number 4

OCGS Membership & New Members

SOCIETY MEMBERSHIP _____________________________________________________________________________ As of 8/3/19 OCGS 439 Active 77 Associate 11 Emeritus 9 Honorary _____ 536 TOTAL NEW MEMBERS _____________________________________________________________________________






Mike Wood Sales Manager Mobile: (580) 819-3988

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July ~ August 2019 | Page 153

WhatYou Missed



Page 154 | Volume 70 Number 4

Thank You To Our Sponsors:

July ~ August 2019 | Page 155

By: P. Paul Denney, Independent Geologist, Colorado Springs, CO Oil and Gas Exploration

The Discovery and Geology of the Potato Hills Gas Field, Latimer and Pushmataha Counties, Oklahoma

Foreword I ended my relationship with the GHK Company in 2008 after consulting for 10 years. Much of that time involved the de- velopment of the Potato Hills gas field. Since 2010, the field was sold and resold to four different operators. In 2018, I was engaged by one of these companies to relate my recollections of the develop- ment and geology of Potato Hills. I was surprised to learn that little geologic infor- mation had been released; few new wells drilled and no maps published. Sanguine Gas Exploration, Tulsa, OK is the present operator.

In 2015, I donated my field files to a local University, those files have subsequently been lost. However, I had retained a Pow- erPoint presentation originally given at a sectional AAPG meeting in Tulsa in 2006. From that presentation I have recovered important geologic displays which have not been viewed since. Fortunately, these were of high quality graphics; unfortu- nately, they are small scale. I have an- notated wells and added explanations to make them comprehensible without mag- nification. Additionally, maps have been updated for recent drilling.

In 2006, GHK had restricted me from revealing the target prospect on the then active GHK #2-34 Mary test well (a pros- pect idea generated by a third party geo- physicist). I am no longer under that con- fidentially restriction, so an interpretation showing that deep well is included with this paper. A final note, I must acknowledge the late Greg Cook’s contribution of management and drilling techniques in the develop- ment of the field. It was wonderful to have been his partner in this enterprise.

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Abstract Shallow production at the Potato Hills gas field was discovered by the Sinclair #1 Reneau in 1960, completed for 1.33 MMcfgd (110.4M cu-m/d) from Ordovi- cian Bigfork Chert, Figure 1. However, it wasn’t until the completion of the GHK et al #1-33 Ratcliff in September 1998 that a major gas accumulation was rec- ognized. The GHK #1-33 Ratcliff well (c W/2 sec.33 T3N R20E) was completed for 35.77 MMcfgd (1.01MM cu-m/d), from the “Ratcliff Sandstone”, a unit of the Morrowan Jackfork Formation. This paper presents information developed dur- ing the GHK Corporation’s development of the Potato Hills Gas Field. The data suggest that Miser, 1929, whose interpre- tation of a fenster of older rocks viewed through a “window” in the north directed Potato Hills thrust fault (PHTF) is essen- tially correct, although simplified. Observations confirm: 1) the Potato Hills were formed by erosion through the Po- tato Hills thrust plate and into the hang- ingwall of the Windingstair thrust fault (WSTF). The outermost outcrop rides on the Potato Hills thrust, the inner outcrop rides on imbricates in the hangingwall of the Windingstair thrust fault 2) late Penn- sylvanian folding of the PHTF and WSTF, is evidence of the emplacement of a fault block in the footwall of the basal Choctaw Thrust fault (CTF), 3) the top of the Jack- fork is an unconformity, 4) the basal sur- face of the Ratcliff Member is an erosional unconformity, 5) recognition of basement- involved extensional faults deforming rocks of Ordovician to Mississippian age beneath the Potato Hills structure.

Figure 1 Stratigraphic Column for the Arkoma Deep-Water basin

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The Discovery and Geology of the Potato Hills Gas Field, Latimer and Pushmataha Counties, Oklahoma, cont. Oil and Gas Exploration

Figure 2 Top Ratcliff Sandstone (Jackfork) Member Structure Map

History of the Potato Hills Gas Field Discovery The Potato Hills Gas Field (Figure 2) was discovered in 1960 with the completion of the Sinclair #1-32 Reneau from 140’ (43m) interval of Big Fork Chert. A con- firmation attempt, the Sinclair #1-33 Mat- tice (section 33 T3N R33E), was drilled

and abandoned in 1961. The near-surface “old rocks”, Ordovician Womble upwards through the Mississippian Arkansas No- vaculite are hard silicates, alternating with soft shale making them seismically reflec- tive. Because of the tight folding, seismic reflections are “brilliantly” dissipated. This is especially true in areas where they are described as a foreland dipping

duplex. The small, tightly folded shal- low Arkansas Novaculite-Big Fork Chert structures make a difficult seismic explo- ration targets. In 1996, the Potato Hills Gas field was rediscovered by the Amoco/ GHK #1-33 Ratcliff. GHK staff, led by Robert Hefner with geologists Russ Cunningham and

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Greg St. Clair, recognized that dipmeters from the Sinclair #1-32 Reneau well and the America Quasar #1-11 Cabe, section 11, T2N R20E, showed opposing dip, indicating an anticline at depth. Because of the surface cover of highly reflective, intensely deformed rocks, seismic record quality is poor and extremely difficult to interpret. The GHK/Amoco #1-33 Ratcliff was drilled on sub-surface geology and spotty, discontinuous seismic reflections. Development of Field: In 1997, prior to production testing, Amo- co elected not to participate in completion of the Ratcliff #1-33. Additionally, Hefner took his exploration team to a new play in Columbia, S.A. To develop Potato Hills, Greg Cook was hired as GHK Operations Manager and the author was engaged as consulting geologist/geophysicist to recommend de- velopment drilling. During these person- nel changes, the Ratcliff well (which had initially tested 3.9MMcfg/d (110.4M cu- m/d)), was frac-treated and came on flow- ing 35.77MMcfg/d (1MM cu-m/d). The well also tested gas from untreated deep Big Fork (Ordovician-age) Chert, and the Cedar Creek (Jackfork) sand. Structure: The field was initially spaced on 640 acres. Considering the anticipated struc- ture and the absence of quality seismic data, this required relatively “long step outs” which were chosen based on a geo- logic model and dipmeter analysis. The simple fold geometry involving Atoka rocks in fields north of Potato Hills, Lynn Mountain, Talihina Northwest and Buffalo Mountain gas fields provided the geologic model. At this time, dipmeters were avail-

able for three wells (#1-33 Ratcliff, #1- 32 Reneau and #1-11 Cabe) in the early Potato Hills field. The construction of dip vs. azimuth plots on these three wells, (Bengston, 1981) defined the structure as an asymmetrical fold with increasingly steep dip, toward the NNW (see Figure 2). Bengstoms Statistical Curvature Analysis Technique (SCAT) also indicated ENE plunge in the Cabe well. With step out drilling, it would take two years to determine that this anticline ex- tended nearly 10 miles in an east-west direction. Early on, it was observed that a common gas-water contact at -5350’ (1631m) was present in the Ratcliff and Cedar Creek zones. During the first three years, only one dry hole was drilled, the GHK #1-Georgia (section 36 T2n R 20E), a penetration determined to have a tight Ratcliff reservoir, although nearly 300’ (92m) above the G-W contact. The generalized description of the seis- mic data across the Potato Hills structure is characterized as poor quality. GHK purchased available existing data for re- processing and recorded confidential data using high-resolution recording parame- ters and equipment. Data quality was little improved, although the spotty migrated seismic events became more useful as ad- ditional wells were completed and used to control geologic interpretation of the seis- mic data. Development drilling proceeded on both ends of the field simultaneously, based on acquisition of new seismic, well data results and dipmeter analysis. Dip di- rection and dip magnitude are shown on figure 2, “Top Ratcliff Member Structure Map”. In contrast to the overlying Potato Hills tightly folded surface structure, the Potato Hills Ratcliff zone reservoir is a relatively

July ~ August 2019 | Page 159

The Discovery and Geology of the Potato Hills Gas Field, Latimer and Pushmataha Counties, Oklahoma, cont. Oil and Gas Exploration

Figure 3a Structural Cross-section A-A’ Potato Hills Gas Field. Early 2006 construction before Chesapeake/GHK #2-34RE Mary was drilled

simple, asymmetric anticline, Figure 3a. On the northern side of the field, the old Sinclair #1-33 Reneau dips 60˚N. Off structure toward the south, the America Quasar #1-11 Cabe well dips 38˚-50˚S. At the # 1-33 Ratcliff discovery location, the dip is 25˚N, increasing with depth. Miser’s, 1929 shallow interpretation is

displayed by Figure 3a. The imbricated Potato Hills thrust fault (PHTF) present on the hangingwall of the WSTF has been eroded through to reveal a north verging duplex structure beneath. The steep north dip beneath the WSTF is caused by roll- over onto the Wigington normal fault (described in the next paragraph). The Cabe #1-11 and the Four Star #1-19 wells

control the south dip panel in the footwall of the WSTF. Dip increases from the top of the structure southwards to 60˚ in the Cabe and even steeper at total depth in the Four Star. These two wells overlie a ramp, above a suspected fault block of foreland facies rocks beneath the basal Choctaw thrust fault.

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Figure 3b Structural Cross-section A-A’ Potato Hills Gas Field Revised 2019

Figure 3b is revised interpretation of Fig- ure 3a, accounting for the re-entry and deepening of The Mary #2-34. In this view, the encounter of a normal sequence of Mississippian-Ordovician foreland fa- cies rocks is depicted. At depth, along the northern side of the anticline, the Wigington normal fault, vis-

ible on Figure 4 positions an upthrown “sliver” of near-vertical Womble thru No- vaculite rocks between the Potato Hills field and the north-dipping Stanley por- tion of the Buffalo Mountain syncline. In the hangingwall of the Ti Valley (?) thrust fault, is a sliver of Ratcliff broken away from and elevated into a vertical position of the Buffalo Mountain syncline floor.

These Ratcliff and Big Fork/Novaculite “fault slivers” had drilling shows and test- ed productive but were of limited extent. The Wigington fault was first recognized in the Wigington #1-1 (section 1 T2N R19E), and has since been drilled in 11 wells. The fault is recognizable as missing section on well log correlations associ-

July ~ August 2019 | Page 161

The Discovery and Geology of the Potato Hills Gas Field, Latimer and Pushmataha Counties, Oklahoma, cont. Oil and Gas Exploration

Figure 4 Structure Contours on Wigington Normal Fault at Potato Hills Field

ated with the increasingly steep north dip onto the Ti Valley thrust fault. Displace- ment is upthrown toward the north. The fault shows imbrications into as many as three branches (GHK 1-25 Triple TMS) and the Wigington into two branches each showing a combined 1700’ (523m) of missing section. The #3-33 Cedar Creek well shows the greatest missing section of

2500’ (769m). Eleven wells have encoun- tered the Wigington (missing section and northward displacement) always becom- ing shallower in depth toward the north. Most of these well encounters have unde- terminable large missing sections. The origin of the Wigington fault is not well understood. It may be an overturned

reverse fault as is found on the northeast side of Wilburton field, or more probable it is a late relaxation feature forming in early Pennsylvanian. A similar feature is prominent at Ryckman Creek field in the Wyoming thrust belt. Figure 5, is a structure contour map on the WSTF. This map was constructed by con-

Page 162 | Volume 70 Number 4

Figure 5 Structure Map on Top Surface of the Windingstair Thrust Fault

touring the easily identified contact of Or- dovician Womble Shale with either Johns Valley or Jackfork formation. The WSTF map shows similar structural closure and plunge to the Ratcliff structure map. Both these maps also correspond closely to the area occupied by the surface Potato Hills outcrop. Taken together, all three maps are suggestive of a deep block uplift beneath

the Potato Hills. A similar block uplift involving the Simpson-Arbuckle forma- tions produces at Wilburton field. This deep structure was the GHK/Chesapeake target, in drilling the #2-34 Mary. They found their objective, but missed the crest. Uplift of Wilburton field probably oc- curred during a rifting event prior to

thrusting, but the flattening of thrust faults across the field and northward dip on those faults, implies the block uplift was renewed in late Pennsylvanian.

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The Discovery and Geology of the Potato Hills Gas Field, Latimer and Pushmataha Counties, Oklahoma, cont. Oil and Gas Exploration

Figure 6 Stratigraphic Cross-section B-B’ of Jackfork Formation

Stratigraphy: The Ratcliff Member reservoir zone is a blocky sandstone with an abrupt lower contact. The cross-section Figure 6 reveals southward thinning (an unconformity) from South Panola field across the Potato Hills gas field. The reservoir is interpreted as a regressive channel deposited across

Carboniferous turbidites. Porosity greater than 10% was determined as necessary for sustained production. Fractures were equally important for production. Maxi- mum fracturing is present along the crest of the anticline and are oriented approxi- mately N-S. GHK took rotary sidewall cores targeted off porosity logs. The pres- ence of fractures was determined from ro-

tary sidewall cores, sonic logs, dipmeters and drilling indications. Northeastward, in the Hope and Princess boreholes, the Ratcliff becomes more shaley. In addition, underlying strata is truncated as the Potato Hills feature is ap- proached. In the gas field, the Ratcliff is a sub-aqueous channel facies that changes

Page 164 | Volume 70 Number 4

Figure 7 Ratliff Member Litholofacies (for GHK # 1-12 Edmonds)

into a shelf sand as one moves north-east- ward toward South Panola field. Romero (2004) studied cuttings and logs from the GHK #1-12 Edmonds, (Figure 7). From her study she describes two li- thologies in the upper Jackfork, 1) fri- able channel sandstones changing into 2) quartz cemented shelf sandstones. These two lithologies are evident on the resis- tivity log of the subject well. Laterally, shaley splays develop at the top of the thick channel sand and grade laterally into the quartz cemented layered sheet sand- stone. Eustatic sea level changes caused by Pennsylvanian glaciation resulted in lowered sea levels and the regression of depositional facies (Romero, 2004). Suneson (2012), extrapolates Romero’s subsurface interpretation and applies it to his surface studies. Suneson recognizes both the friable channel facies and the lay-

ered sheet sands on the surface. He calls these, respectively, turbidity channels and sheet sands. The Ratcliff looks to be a sub-aqueous regressive channel sand body that moved southward across a deltaic shelf that ex- tends into a deep-water fan environment (personal communication, John Coughlon, March, 2019). Figure 6 shows the Upper Jackfork (Ratcliff) at Potato Hills field to be a massive sand with an abrupt lower contact. In fact, the lower contact is an angular unconformity. Laterally toward S. Panola field, this sand becomes increas- ingly shaley and grades into what Romero and Suneson call the layered sheet sand. Across this display, the thickness of the Ratcliff is relatively constant (authors note: the Cabe well has been displayed with vertical scale reduced to account for steep dip).

The GHK #1-33 Ratcliff is herein for- mally designated as the type section of the economically important, Ratcliff Member of the Jackfork Formation. The sand in that well is found between 5100-5400’ md (1555-1646m ) in the GHK #1-33 Ratcliff gas well as shown in Figure 6. Interpretation of the Potato Hills Struc- ture The deep Chesapeake/GHK #2-34 Mary re-entry drilled 9600’ (2926m) of Stanley formation overlying reworked Arkansas Novaculite and 5300 feet (1615m) of Mis- sissippian through Ordovician rock before encountering the Ti Valley thrust fault at 19400 feet (5913m) measured depth (Re- fer to Figure 3). The well repeated Novac- ulite-Missouri Mountain-Big Fork before cutting the Choctaw Thrust Fault at 22500 feet (6860M).

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The Discovery and Geology of the Potato Hills Gas Field, Latimer and Pushmataha Counties, Oklahoma, cont. Oil and Gas Exploration

The Mary #2-34 requires a comprehen- sive discussion. Refer back to Figure 3b: Wells drilled to 26,000 feet (8000 m) are rare, especially those drilled far south into and through the Ouachita facies of rocks. The resistivity log shows the well drilled an unusually long section of Arkansas No- vaculite-Big Fork Chert in the footwall of the Wigington fault before cutting a basal thrust detachment into shelf facies Simp- son-Arbuckle rocks. The long panel of Arkansas Novaculite was also encountered in the lower section of the GHK #1-19 Four Star well. In the two wells, these rocks lie on the down- thrown side of the Wigington fault and with the wells deviating southward, the bit followed the bedding. Undulations in dip caused the Mary well to drill in and out of Novaculite and Big Fork rocks. The upthrown block of Novaculite-Big Fork was encountered by the GHK #1-26 Leonard at 13,000 feet (4000 m) where it tested gas. Beneath the deep-water Or- dovician rocks, the Leonard drilled near- vertical Jackfork in the hangingwall of the Ti Valley fault and the overturned limb of the Buffalo Mountain syncline. References Bengston, C. A. 1981, Statistical curva- ture analysis techniques for structural interpretation of dipmeter data. Bul- letin of the American Association of Petroleum Geologists, 65, 312-332 McClay, K.R., 1981, Thrust and Nappe Tectonics, Geological Society Special Publication, No. 9

Below the Choctaw thrust fault (CTF), the wellbore found shelf facies Caney Lime- stone-Woodford Shale section. A small thrust fault at -22500 feet md (-6923 m) repeated a 748’ (728m) section of Caney andWoodford and continued into a normal section of Hunton-Sylvan-Viola-Simpson. Below the Simpson 800 feet (244m) of Arbuckle formation was drilled. The up- per Arbuckle, West Spring Creek Mem- ber was tested and determined to be tight, shaly dolomite. Although the Mary #2-34 tested tight, there is potential for production. Wilbur- ton field is not a structure filled to the spill point. Wilburton has a 1350 foot (411m) gas column with at least 750’ (229m) clo- sure beneath the G/W contact at -13250’ (4039m). Permeability was found to be a “crinkle” facies (karsted collapse brec- cia) enclosed in non-permeable dolomite. Figure 3b shows that the Mary reached the Arbuckle in the footwall of a 748’ (229m) thrust fault. A lateral move can gain 750’ (229m) of structure in the hangingwall block. Additional structural advantage can be found on the true crest of this deep structure. As with all of the Potato Hills, seismic reflectivity is of limited use.

Sub-surface geology using all existing data (well data, dip indicators, and vari- ous types of available seismic), combined with innovative thinking will find the high point on this structure. Undiscovered Potential at Potato Hills The known gas-water contact limits the potential for passed-up Ratcliff. However, potential structural and stratigraphic traps down-dip have not been tested. Addition- ally, Novaculite and Big Fork potential is significant. The Sinclair #1 Reneau reportedly produced 3.4bcfg at 2400 feet (732m). Most penetrations into the shal- low hangingwall of the Potato Hills have probably been drained or pressure deplet- ed due to lack of an upper seal. However, the deeply covered area downdip around the Potato Hills has not been explored. A major gas field in an under-drilled area should attract exploration. However, the lack of understanding of the geology of Potato Hills has disguised the potential value. Two hundred fifty BCF produced and another 50 BCF proven. The oil equivalency of 50 MBO, is surely of inter- est to the industry.

Romero, G.A., 2004, Identification of Ar- chitectural Elements of Turbidite De- posits, Jackfork Group, Potato Hills. unpublished M.S. Thesis, University Oklahoma Slatt, R.M., A.M. Garich-Faust, G.A. Romero, 2005, Potential Stratigraph- ic Reservoirs in the Morrowan Jack- fork Group, Southern Oklahoma in Circular 111, Symposium, Andrews, R. Editor

Suneson, N.H.,et al, 2005, Stratigraph- ic and Structural Evolution of the Ouachita Mountains and Arkoma Ba- sin...., in Guidebook 34, Oklahoma Geologic Survey Suneson, N.H. Shale Shaker, July/August 2012 ogy/pdf/neilarkomabasinshaleshake. pdf

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Biographical Sketch P. Paul Denney studied geology at Univ. California, B.A. 1965, and Univ. Arizona, M.S.1967; his first position in the oil and gas industry was with Standard Oil of Texas (an affiliate of Standard of California) in the East Texas Basin. The reorganization of Socal into Chevron, dissolved Sotex and brought Denney to Oklahoma City. In Oklahoma, his first assignment was in the NE Ardmore Basin working the frontal Wichita Mountains when the Mobil Towho wildcat was drilled at Apache Oil Field, proving a folded foreland-type structure as opposed to a thin-skinned overthrust. Denney mapped the impending Chickasha Marchand trend before it’s discovery but was disappointed when Chevron refused to lease. NE Verden (Marchand SS) field subsequently expanded into the 100MMbo Morrow-Springer-Chickashaw trend. Denney was marginally involved in the Hunton discovery at Mills Ranch and other Hunton fields in the western Anadarko basin.

P. Paul Denney

Chevron closed the OKC office in 1971 and Denney was assigned to the Rocky Mountain Division where he worked the Wyoming Thrust Belt as a geophysicist/geologist leading to the Chevron/Amoco discoveries in 1975, and later with The Anschutz Corporation at East Anschutz Ranch in 1979. Denney worked with Amoseas Indonesia (Jakarta) between 1975-78. Denney went on his own in 1980, consulting for majors and large independents mostly within the continental U.S. GHK hired Denney as a long term consultant for development of the Potato Hills gas field and exploration in the western Anadarko Basin in 1998. With retirement not a desired option, Denney has taught at the community college level for the past 3 years, while still working to identify gas prospects in the Arkoma Basin. For comments or questions email:

July ~ August 2019 | Page 167

By: Andrew Cullen, Warwick Energy My Favorite Thin Section My Favorite.....

Thin Section: The Caney Sandstone from Philip’s Creek- One of Rick Andrews’ Favorite Outcrops.

Prolog : I recently went through the last two decades of the Shale Shaker searching for the origins of the “My Favorite Out- crop” series. Charles Gilbert’s discussion of the development of tor topography in the Permian-age Post Oak Conglomerate in 2009 (Shale Shaker v.59) represents

the informal start of a nearly unbroken set of short articles specifically focused on outcrops. Credit for this features’ official start goes to Julie Chang for “My Favorite Outcrop - Dodds Creek Sandstone, Osage County, OK” in the July-August 2010 is- sue, volume 61. Julie’s name should be

familiar to most Oklahoma geologists, as she and Tom Stanley with the Oklahoma Geological Survey have co-produced 15 quadrangle geological maps in the State. In this issue the Shale Shaker staff are thrilled to rebrand this long-running

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technically informal series as “My Fa- vorite You-Fill-The Blank .” Submis- sions could include, but are not limited to, thin sections, seismic lines, wells, and SEM images. We seek your involvement and want to share what our members think is insightful, exciting, cool or quirky from entire spectrum of the Geosciences. It is only fitting that in the first installment in this revamped series a thin section from one of Rick Andrews’ favorite outcrops takes center stage (Andrews, 2012). Overview : Philips Creek incises the south limb of the Arbuckle Anticline and empties into the Caddo Creek Reservoir (Figure 1a). Heading south towards Ard- more, I-35 cuts through classic ridge and valley topography formed by differential weathering of Early Paleozoic carbon-

ate and clastic strata, respectively. The Mississippian-age Sycamore Formation is well exposed on the last ridge on the back limb of the Arbuckle Anticline (Miller and Cullen, 2018). On the west side of I-35 coming down the dip slope of that last ridge outcrop there is a modest iso- lated hill, hereafter informally referred to as Philips Hill (Figure 1b). Philips Creek and feeder gullies cut into the east end of Philips Hill exposing approximately 300ft of the Mississippian-age Caney Shale. This is unarguably(?) the best exposure of Caney Shale in the entire State. Andrews’ 2012 article includes a measured section with hand-held gamma ray log and a brief discussion of the stratigraphic succession in which he notes that the lower Caney is mud-rich but has a distinct thin sandstone bed; up section the Caney becomes more siliceous and has several thin siltstone and chert beds. The basal section at Philips Creek is probably correlative with Ahloso Member of the Caney Shale which is Low- er Visean in age (Boardman et al., 2009). The organic-rich mudrocks in the Caney Shale, which are correlative with the Bar- nett Shale in the Fort Worth Basin and the Fayetteville Shale in Arkansas, were tar- geted in the early phase of in shale-gas ex- ploration in Oklahoma but were generally too ductile to be commercially stimulated (Andrews, 2007). Recently, however, as completion technology has progressed, there have been encouraging well results in Johnston and Love Counties. Caney Sandstone – Philips Creek : I first visited Philips Creek to sample the Caney Shale for a research seminar with the Uni- versity of Oklahoma that addressed the provenance and delivery of the volumi- nous amount of silt-sized angular quartz to the lower Mississippian intervals of central and southern Oklahoma. Several samples of carbonaceous silty mudrock were collected from a nicely developed cut bank (Figure 2a). The sandstone sample was taken from one of the many blocks of float on a point bar where blocks of Caney mudrock are also present (Fig-

ure 2b). The sandstone is a friable well- sorted, fine to medium-grained quartz ar- enite with limonitic weathering rinds. Our research program included detrital zircon dating, which at $2000 per sample dic- tated a prudent use of a limited analytical budget. The question immediately arose of whether the sandstone sample was truly from the Caney or just a “river rock” from one of the Simpson Group sandstones up- stream. I argued that because the Simpson sandstones tend to be weakly indurated, it was improbable that coherent blocks up to a foot long would survive transport more than a mile down creek in flash floods. Putting my money and mouth in the same place, I agreed to pay for the analysis of the sandstone sample. Nonetheless, I was challenged to find the lower Caney sand- stone in place and made two more visits to the Philips Creek area where I found sev- eral areas of colluvium about 200ft long and 10ft wide composed entirely of peb- bles and cobbles of sandstone similar to the sandstone blocks in the creek (Figures 2c and 2d). The only place where I have seen the Caney sandstones in place, how- ever, is on a steep dip slope at the south side end of Philips Hill (Figure 3) where the creek E-W after making an abrupt bend (Figure 1b). My Favorite Thin Section :At first glance, a thin section of the Caney sandstone ap- pears to be a geology student’s ideal easy answer. Even without looking through a petrographic microscope, it is apparent from the both the hand sample and thin section itself, that this is a well-sorted, rounded orthoquartzite with about 15% intergranular porosity (Figures 4a and 4b). XRD analysis (Figure 4c) confirms an extremely pure sandstone, 98.5% quartz! What could be easier on a test? Next ques- tion please. It is under the microscope that such simplicity is challenged by more de- tailed observations (Figure 5). 1. Note the beautiful and pervasive syn- taxial quartz overgrowths that rim the quartz grains. These rims grew into

Figure 1 a) Location map for Philips Creek and the Last Ridge outcrop. b) Topographic map of study area showing geological formations and features, including Philips Hill.

July ~ August 2019 | Page 169

My Favorite Thin Section The Caney Sandstone from Philip’s Creek- One of Rick Andrews’ Favorite Outcrops, cont.

Figure 2 a) Cut bank along Philips Creeks with Caney Shale exposure b) Cobbles of float on point bar on Philips Creek c) Block of sandstone in colluvium above gully feeding into Philips Creek d) Fresh surface on cobble from sandstone in colluvium.

open pore space and post-date depo- sition. The original grains were very well rounded, which suggests a re- cycled origin. 2. Many of the quartz grains are ellipti- cal, not spherical. Some of the grains were sutured into composite a grain before being deposited, which gives

them an elongate shape. This ob- servation indicates the grains were originally more deeply buried prior to uplift, erosion, and deposition as the Caney sandstones, again supportive of a recycled origin. 3. The cores of the grains are fractured and have numerous fluid inclusions,

whereas the rims are relatively free of inclusions and fractures. Quartz ce- mentation is generally interpreted to take place at elevated subsurface tem- peratures (~80 o C to 100 o C). RockEv- al data from three Philips Creek mu- drocks have a mean VRE from Tmax of 0.43% (Table 1, Warwick Energy unpublished data). Brian Cardott,

Table 1

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Figure 3 Photograph of dip slope of Caney on the south side of Philips Hill where two thin sandstone beds crop out, outlined in thin dashed lines.

personal communication, reports mean random vitrinite reflectance is 0.48% Ro with values between 0.43- 0.55% Ro (n=20). This low level of maturity suggests that quartz cemen- tation occurred at relatively low tem- peratures or that fluids with elevated temperature migrated through the Caney sandstones. 4. There are small amorphous brownish blebs in the pore space between some of the quartz grains and few blebs be- tween the rim and core. The compo- sition of these blebs is unknown, but

their shape and color strongly sug- gest they are oil or bitumen (Figure 6 and inset Figure 5). This would not be surprising; along the Philips Creek some of the Caney mudrocks have a faint hydrocarbon odor on freshly excavated surfaces. One sample has excellent quality source rock. Epilog - Additional Thoughts and Com- ments : Sampling for detrital zircons, cor- ing paleomagnetic sites, and cutting thin sections remind me of Forrest Gump’s maternal proverb about a box of choco- lates. “You never know what you’re gonna

get.” The sandstone thin section has very interesting features in what appears to be a boring rock; one only needs to look closely. With respect to zircons, I was also rewarded for the risk I took in agreeing to pay for the detrital zircon analysis of the sandstone. The sample yielded abundant zircons with age distributions indicating three distinct basement source terranes: Superior, Granite-Rhyolite, and Grenville (Figure 7). The Caney sandstone zircon age spectra bears resemblance to the Or- dovician-age Blakley and Crystal Moun- tain sandstones in the Ouachita Mountains (McGuire, 2017), but has an additional,

July ~ August 2019 | Page 171

My Favorite Thin Section The Caney Sandstone from Philip’s Creek- One of Rick Andrews’ Favorite Outcrops, cont.

Figure 4 a) Photo of the Caney sandstone sample b) Photo of sample of thin section c) XRD results of Caney sandstone.


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Figure 5 Photomicrograph, plain light, of Caney sandstone with blue epoxy in pore space. Dashed black lines show original grains; red dashed lines are fractures; S, grain sutures; R, quartz overgrowths; O, possible hydrocarbons; F, altered feldspar grain.

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July ~ August 2019 | Page 173

My Favorite Thin Section The Caney Sandstone from Philip’s Creek- One of Rick Andrews’ Favorite Outcrops, cont.

Figure 6 More detail photomicrograph of Caney sandstone sample showing probable oil droplet (O); note that several grains appear be composite strongly sutured grains from prior burial and exhumation.

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