Abstract: Atoka Gas in Southern Cottle and Northern King Counties, Texas
H. S. Edwards
The Atoka gas production in southern Cottle and northern King Counties, Texas, occurs on the flanks of the pre-Pennsylvanian northwest-southeast trending "Masterson arch." The arch is named for the Masterson Ranch in the extreme western part of the Baylor basin near the Knox and King County line. This structural trend becomes progressively deeper northwestward through the Juniper, JY, Providence, Prudence, Stescott, Tippen, Prothro (Ramsey structure) and Wilie fields where it joins the east-west Matador arch at the structure known as Narcisso on the Cottle and Motley County line.
The producing Atoka sandstones or conglomerates consist of medium to coarse predominantly subangular quartz grains with traces of glauconite. These sands which form stratigraphic traps were deposited as offshore sand bars on the northeast and southwest flanks of the Masterson arch. The Atoka conglomerates are erratic because of deposition on a steeply dipping erosional surface with abrupt changes in dip. The entire Atoka Formation from the base of the Caddo Limestone to the top of the Mississippian limestone consists of very hard, dark gray to black calcareous shales with the conglomerate present anywhere within this section. The Atoka shale is very thin and void of conglomerate on the axis of the arch, although basinward the section thickens and conglomerates are present.
The Providence gas field in extreme southeast Cottle County was discovered in October 1973, with the successful completion of the "Gus" Edwards 1 J. J. Gibson. The discovery well was a natural completion for an absolute open flow of 10,200 MCFD (289 M cu m) from perforations at 6,134 to 6,140 ft (1,869 to 1,871 m) and 6,151 to 6,161 ft (1,875 to 1,878 m); GOR of 50,750:1; gravity 65°; surface shut-in pressure of 2,132 lb and BHP at 6,150 ft (1,874 m) 2,649 lb; Btu content on dry basis of 1,211. Development to date reveals a gas column of 141+ ft (43 m) with no indication of water. However, water is present at different subsea depths in the other gas fields on this trend. The absolute open flow for the 14 producing gas wells ranges from 890 to 66,500 MCFPD (25 to 1,883 M cu m) wit an average of 11,600 MCFPD (328 M cu m). The porosity ranges from 15 to 21% with average pay thickness of 18 ft (5.5 m).
AAPG Search and Discovery Article #90970©1977 AAPG Southwest Section Meeting, Abilene, Texas