Preliminary Investigation of Ground-Water Occurrence in the Atoka Formation of Pope and Faulkner Counties, Arkansas

Abstract

One hundred and twelve wells having drillers\u27 logs were studied in Pope and Faulkner counties. Sixty-six of the wells produced water from shales and siltstones of the Atoka Formation while 46 produced from interbedded Atoka sandstones. Drillers\u27 estimated well yields ranged from 1 to 100 gpm, but the median yield was only 9 gpm. Well depths ranged from 30 to 337 feet with a median depth of 100 feet. Ground-water is usually obtained from a series of low-producing confined aquifers of low artesian pressure. Pressure head and production were shown, statistically (a = .01), to decrease with increasing well depth. This indicates that fractures and bedding-plane partings become more tight with depth associated with the increasing lithostatic pressure. Ground-water flow directions are generally to the south towards the Arkansas River with static water levels strongly conforming to the topography (a = 0.001). A resistivity study was performed near Guy in Faulkner County to investigate the hypothesis that production is largely controlled by fracture porosity. The tri-potential resistivity technique was utilized to verify the presence of suspected fractures delinated from aerial photographs. Existing wells in the area produce estimated yields of 1 to 20 gpm. The well located in this study on verified fractures produced 120 gpm

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