Successful Application of Viscoelastic Fluid Technology to Stimulate a Gas Storage Reservoir

Abstract

Abstract Columbia Gas Transmission operates two groups of natural-gas storage fields approximately 50 miles northeast of Columbus, Ohio. The Silurian-age Clinton sandstone formation in both fields varies significantly in thickness and reservoir quality. Although the gross Clinton interval is fairly uniform, it can include one to three separate sand members. Reduction in storage-well performance over time dictates the need to periodically stimulate, or even re-stimulate the wells. Fracture stimulation is often required to restore well performance. The objective of the hydraulic fracturing treatments in these wells is to obtain a short, highly conductive propped fracture past the damaged area. Fracturing models are used to determine the optimum tip-screenout treatment design based on individual well characteristics. Several fracturing fluids have been used in the attempt to achieve the optimum fracturing treatment. Previously, the best results were seen with borate-crosslinked fluids using nitrogen assist. With recent advances in fracturing-fluid technology, conventional borate-crosslinked fluids can be replaced with high-performance viscoelastic fluids, which reduce fluid damage to the proppant pack and formation. The viscoelastic fluid has excellent proppant-transport properties and predictable break times. Three wells, two in Group I and one in Group II, were selected as candidates for fracturing with the viscoelastic fracturing fluid. Fracturing models were used to design a treatment that would result in similar fracture geometry as the borate-crosslinked fluids. This resulted in up to 40% reductions in total fluid requirements and up to 65% reductions in pad fluid volumes. All three wells were fracture-treated with the designs obtained from the fracture models. Fluid volumes recovered, flowing pressures, and choke size were all recorded during flowback and compared to values from offset wells. This paper details the properties of the viscoelastic fracturing fluid, fracture designs, and post-fracture results of the wells stimulated with the viscoelastic fluid.