Abstract Horizontal well drilling and production have been increasingly important to the oil industry in recent years. The potential of significant increase in oil or gas production from a horizontal well will be very attractive as drilling and completion costs diminish and new technologies are developed to address problems concerning wellbore stability and formation damage. This paper presents a successful case analysis on borehole stability conducted before an openhole recompletion was performed in an existing cased hole for increased oil production. The North Sunshine May No. 4 well located in the Big Horn Basin of Wyoming, was originally completed as a vertical well in 1977. In late 1987, the well was sidetracked and laterally extended to a nearly horizontal wellbore. The 1000-ft lateral extension exposed 850 ft of the reservoir sands for production. The pay zone was cased with 4-1/2" liner. However, the production rate was not as high as originally anticipated. A decision was made to explore the possibility of pulling the slotted liner from the well and leave as an openhole completion after cleaning the reservoir portion of the hole. Based on rock mechanics principles, we conducted openhole stability analysis using high-angle drilling and core recovery data from the well. The analysis also considered the effect of reservoir depletion on openhole stability. The results predicted that the rock strength for the reservoir sands was great enough to keep the horizontal section open with little or no formation support during oil production, following the openhole recompletion operation. Field results after removal of the slotted liner have confirmed this finding. Some detail about the completion for oil production is also described herein.