Sustainable Casing Design for Water Supply Wells: Fewer Casings, Faster Drilling, and Protected Aquifers

Abstract

Water supply wells often require large open-hole intervals across aquifers to deliver high yields with high-capacity pumps, which traditionally necessitates heavy multi-string casing. This abstract presents a new casing configuration that streamlines the well design by using two successive open-hole sections in place of conventional cemented casing strings. The result is a technically innovative and more sustainable well architecture that meets all performance and integrity requirements with fewer materials and operations. The new design places a 13 3/8″ casing above the first aquifer, then drills a continuous 12 1/4″ hole through both aquifers down to the well's total depth. A 9 5/8″ pre-perforated liner is installed across the upper aquifer, and two 9-5/8″ swell packers are used to isolate the shale layer between aquifers. This eliminates the need for a second cemented casing string and avoids under-reaming operations, simplifying the well architecture. The new casing design meets all water well requirements using only one cemented section plus two open-hole sections with different hole sizes. It provides a full-size 12-1/4″ hole below the liner shoe without any under-reaming, improving operational efficiency. Unlike the previous heavy design (which required multiple cemented casings and caused cement invasion that sometimes damaged the aquifer formation or nearby wells), the new design avoids such reservoir damage by using an off-bottom perforated liner at the upper aquifer, while the lower aquifer is produced through a large open hole. The pump setting depth remains unchanged, preserving production performance. This simplified configuration reduced drilling time by 30% through the elimination of an entire casing string and its associated cementing and perforation operations. It also lowered the rig capability requirements, allowing the use of a smaller rig for additional cost and emissions savings. By using fewer steel casings and less cement, the design minimizes material consumption and environmental footprint. This paper provides detailed analysis from engineering and planning through execution, field results, and key lessons learned for future applications. This is a first-of-its-kind implementation where open-hole completion techniques (a pre-perforated liner and swell packers) fully replace a cemented casing string in a water supply well. The paper delivers a novel methodology that greatly improves well construction efficiency and sustainability (significantly less steel, cement, and energy usage) without compromising well performance, thus expanding the industry's drilling design toolkit.