A joint research project between the Arkansas Geological Survey (AGS) and Shell Exploration & Production Company (SEPCO) was undertaken to report the findings of three exploration wells drilled by Shell during the 1980s in the Arkansas portion of the Ouachita Mountains. Shell recognized several potential targets in the Ouachita fold and thrust belt of Arkansas and drilled three wildcat wells to test their hydrocarbon potential. The three wells were designed to test the reservoir potential of the Carboniferous sandstones in the Jackfork and Stanley Formations (Rex Timber well, Clark County); the Lower Mississippian-Devonian Arkansas Novaculite and the Ordovician Bigfork Chert (Arivett well, Pike County); and the Ordovician Crystal Mountain Sandstone and Bigfork Chert (International Paper well, Hot Spring County) (Plate 1; Figure 1). The results and conclusions from these wells are published in a three part series of information-circulars at the AGS. As the final of the three publications, this report focuses on the International Paper No. 1-21 well located in S21-T4SR20W.