The Effect of Sulfur Deposition on Gaswell Inflow Performance

Abstract

Summary Deposition of solid elemental sulfur in the formation may significantly reduce the inflow performance of sour-gas wells. The key operational and reservoir parameters that influence the magnitude of impairment by sulfur deposition were identified through the derivation of an analytical expression for the rate of sulfur buildup assuming idealized flow conditions. A methodology for the use of conventional, black-oil reservoir simulators was subsequently developed to permit the investigation of sulfur-deposition processes for specific reservoir descriptions and well operations. The rate of sulfur buildup in the formation was shown to be inversely proportional to the square of the radial distance from the well. As a consequence, the magnitude of sulfur deposition is highly sensitive to well skin— the lower the skin, the farther away from the well the deposition occurs and the lower the sulfur-buildup rate. Nonuniform deposition over the pay interval (owing to reservoir layering or uneven stimulation) was shown to accelerate the impact of sulfur deposition. A field case involving early decline in well production caused by sulfur deposition was successfully history-matched with the simulation model developed in this study.