First Successful Application of Geosteering Drilling in Narrow TVD Window: A Case Study on a Deep Horizontal Gas Well in Bolivian Foothills

Abstract

Bolivia produces hydrocarbons from the Tertiary, Carboniferous, and Devonian formation systems. A horizontal well was planned to be drilled in a sand gas reservoir with reduced thickness to increase reservoir contact and gas production. The plan included an estimated 400-meter horizontal interval that was determined as the ideal length to be completed with sand control using 125-micron filters along its entire length. To achieve this plan and navigate through the reservoir with a 6-inch diameter bit, a vertical pilot well was drilled to acquire the necessary information, such as formation dip and petrophysical characteristics of the reservoir through wireline logs in an 8.5-inch open hole section. Various difficulties were encountered during the execution of the build section with an 8.5-inch bit, such as poor directional control, low ROP, high torque, and differential sticking, which were overcome through a detailed analysis of the unplanned events. This paper shows all the steps that led to successfully drilling a horizontal well through a Devonian sand formation with a narrow TVD window for the first time.