Abstract

There are aggressive wells in Canada, Germany, and the Middle East that have high temperature, high H2S and CO2 content, and which produce several tons of elemental sulfur each day. These wells must be produced with co-injection of sulfur solvents to prevent the plugging of the well bore. As one might expect these wells can also be highly corrosive and chemical products must also include corrosion inhibitors to extend the lifespan of the wells. Qualification of sulfur solvents with corrosion resistant properties is the key to mitigating the risk of these assets. The qualification process can be challenging since laboratory testing under so harsh conditions requires addition of liquid H2S and liquid CO2 to the autoclaves at room temperature. This process requires equation-of-state calculations to model the contents of the autoclave at room temperature to achieve at-temperature conditions.

This paper addresses one such qualification where the field conditions were predicted to be extremely sour with 35% of H2S, 9.5% of CO2, and a total pressure of 3400 psi at bottom hole. Temperatures were expected to exceed 300°F. The wells are also expected to produce significant amounts of elemental sulfur (>100 lb/MMScf). A combination sulfur solvent with corrosion inhibitor product was developed specifically for this sour gas field. The sulfur uptake, boiling point, emulsion tendency and the corrosion inhibition performance of the new product were evaluated in the laboratory.

Introduction

Many operating companies are reluctant to produce sour gas fields because of the high cost of treating the gas to remove H2S and other contaminants to meet the gas specification for sale. However, as sweet fields are being depleted, more and more sour oil and gas wells are being developed. At high H2S concentration and high temperature, H2S may dissociate and form elemental sulfur. ¹

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