Overview

The Caney shale in the Arkoma Basin is the stratigraphic equivalent of the Barnett shale in the Fort Worth Basin. The formation has become a gas producer since the large success of the Barnett play. Caney shale is primarly found in southern Oklahoma near the Texas border and equivalent to the Barnett shale, while the Woodford that is found all over Oklahoma is an older geological unit. According to an AAPG Explorer article, Brian Cardott says, “One of the reasons the Woodford has been so predominant over the Caney Formation, which is the equivalent of the Barnett shale in Texas, is that in Oklahoma the Caney has a clay-rich lithology that absorbs the fracture energy.” On the Oklahoma side of the Arkoma, the shale-gas plays are newer and less well defined. They target the Caney Formation, age-equivalent to the Barnett, and the older Woodford shale. Emphasis on shale-gas in the Midcontinent has come from the Barnett shale in the Fort Worth Basin. Barnett development began with vertical wells and big fracs, then moved to horizontal wells. Over the years, operators in the Barnett accumulated a wealth of knowledge about shale gas and now every Midcontinent exploration company has been looking for, quote, the next Barnett shale.

The Woodford was featured in an earlier UNGR feature, January 2007, so the information included in this issue for the Woodford is for the last year or two. Less has been published on the Caney but I have included selected references at the end. The explosion in the Woodford can be seen by the selected references just since 2007 after the Caney references. The most current and accurate data can be found on the Oklahoma Geological Survey website which includes presentations from past workshops and particularly from Brian Cardott’s publications and Dan Boyd’s yearly updates. For further in-depth information watch for Hart Energy’s Arkoma Play Book, which should be available the end of March or beginning of April.

U.S.G.S. Arkoma Basin Province (062) By: William J. Perry, Jr.

Introduction

The Arkoma Basin Province includes portions of west-central Arkansas and southeastern Oklahoma and includes an area of about 33,800 sq mi. The maximum length of the province is about 315 mi, east-west, and the maximum width is about 175 mi, north-south. In Arkansas the province is bounded on the north by the Ozark Uplift and in Oklahoma it is bounded on the north by the Cherokee Platform. The northern part of the province is a major foreland basin, the Arkoma

Basin, developed in front of and north of the Ouachita Fold and Thrust Belt. The exposed part of this fold and thrust belt forms the southern part of the province. The Arkoma Basin is characterized by down-to-the-south normal faults which affect Early Pennsylvanian and older rocks. The Ouachita folded and thrust-faulted sequence consists primarily of younger Paleozoic deep-water siliciclastic turbidites and older Paleozoic radiolarian cherts and shales. Sedimentary rocks in the Arkoma Basin range in thickness from 3,000 to 20,000 ft and consist primarily of pre-Mississippian carbonate shelf deposits, organic-rich Mississippian marine shales and Pennsylvanian fluvial deposits. Almost all of the Early and Middle Pennsylvanian section is represented in the basin. http://certmapper.cr.usgs.gov/data/noga95/prov62/text/prov62.pdf

Caney Shale, Arkoma Basin, Oklahoma By Forgotson, Jamas M.

Oklahoma University, Norman, OK

The Caney shale, Chesterian age, was deposited in the Oklahoma part of the Arkoma Basin one of a series of foreland basins that formed progressively westward along the Ouachita Fold Belt from the Black Warrior Basin in Mississippi to basins in southwest Texas. The Arkoma Basin in Oklahoma is in the Southeast corner of the state north and northwest of the Ouachita Mountains. The Caney thickens toward the southeast from 90' at its northwest edge to 220' along the Choctaw fault in the south. It can be subdivided into 6 intervals based on characteristics of the GR, density and resistivity logs. The Caney dips southward from a depth of 3000' in northern McIntosh County, Oklahoma to 12,000' just north of the Choctaw thrust. Reported average TOC values for the Caney Formation range from 5% to 8%. The TOC values range from 3% to 8% for different members of the Caney. The R0 values range from 1.7 at the northwest edge of the gas window to 3.4 just north of the Choctaw thrust. TOC values show linear correlation with density. Mud log gas shows have a strong correlation with desorbed gas values that range from 120 to 150 SCF/T. Estimates of GIP for the Caney range from 30 to 40 BCF/ section. Only one Caney completion reported an IP over 1000 Mcf/d. Other vertical completions have ranged from 50 to 100 Mcf/d. The Williams Layman 1-27 horizontal completion declined from an IP of 822 Mcf/d to 180 Mcf/d in one year and could produce at 80-100 Mcf/d for an extended period.

Woodford Shale Gas in Oklahoma By Charles W. Wickstrom

AAPG Annual Convention, San Antonio, Texas, April 20-23, 2008

Abstract

The Woodford shale in Oklahoma has produced hydrocarbons since 1939; however, it was not until 2004 that drilling and completion activity increased from an average completion of 2 wells per year to 35 Woodford completions. In 2007 over 200 horizontal Woodford wells have been drilled and completed. The majority of activity is in the Arkoma Basin with the most successful wells being drilled in Hughes and Coal Counties where the shale is 150' thick. The average maximum month daily rate is reported at 2.5 MMCFG/D and the expected ultimate recovery is estimated to be 3.0 BCFG/Well. The average cost of drilling and completing a horizontal well in the Arkoma Basin in $4.5MM. True vertical depths (TVD) range from 7,500’ to 8,500’ and the laterals average 2,500’ in length. The wells are completed with multi-stage high volume slick-water fracs and casing is cemented to TD. There are six pilot projects underway to determine if this area will be developed on either 80 or 40 acre spacing. In 2007 there are forty-two (42) drilling rigs active in the play in the Arkoma Basin, all drilling horizontal wells. The play is now being extended into two additional basins, the Ardmore and the Anadarko. In the Ardmore Basin the initial concern is that it may not be in the dry gas window. In the Anadarko Basin there are two concerns. The first is the thermally maturity and the second is the depth of burial, TVDs of 12,000’ or more. Vertical and horizontal wells are being drilled and completed in both of these basins and these questions should be answered by the time of this presentation in 2008.

First Crisman Report on Shale Gas in the Arkoma Basin, By Peter P. Valko, August 2008

http://www.pe.tamu.edu/valko/public_html/course_material/2008oct14sem/semsupp/ppt/FirstArkoma.pdf

In Oklahoma, gas shale reservoirs consist primarily of the Caney and Woodford shales. From these unconventional reservoirs most hydrocarbon production occurs in the southeast part of the state in the Arkoma Basin. In this province, the main producing corridor of gas shale occurs within a trend starting in Coal County and extending northward through Hughes, Pittsburg, McIntosh and Muskogee counties. Scattered oil and gas production also occurs in the southcentral part of the state in the Ardmore Basin (Andrews, 2007). The Woodford shale is of Devonian age and extends from southern Kansas, through Oklahoma and into west Texas. It is easily identified by a very high gamma ray streak and is 50- 300 ft thick. Completions have been made from depths of 900 ft in northeast Oklahoma to 13,000 ft in west Texas. The Caney Shale is a formal subsurface formation name and is largely equivalent to the Fayetteville Shale which crops out in the Ozark Uplift of northeast Oklahoma. Stratigraphically, it is roughly equivalent to the Barnett Shale of north Texas but is probably much different in composition. In the Arkansas part of the Arkoma Basin the most promising shale reservoir is Fayettevilleshale which lies between 2000 and 6000 ft deep and ranges between 75 ft and over 300 ft in thickness. The Fayetteville shale is Late Mississippian – Chesterian in age. Both the depth and thickness increase from the west to the east

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