Assessment of Using Copper Nitrate for Scavenging Hydrogen Sulfide While Drilling Sour Horizontal Wells

Abstract

The solubility of hydrogen sulfide (H2S) is very high in different liquids such as water or liquid sulfur. The existence of H2S results in local corrosion and causes cracking to the steel even if the concentration of H2S is low. The objectives of this paper are to (1) evaluate copper nitrate as an H2S scavenger while drilling sour horizontal and multilateral wells and (2) investigate the effect of copper nitrate on the drilling fluid rheological properties and drill pipe corrosion. The obtained results showed that by adding the copper nitrate (1 lb/bbl) to the drilling mud there was no change in the shear stress–shear rate behavior, and the yield point (YP) plastic viscosity (PV) ratio was increased by 20% indicating good hole cleaning. In addition, the filtrate volume reduced by 26% and the filter cake thickness decreased by 50%. The new formulation of the drilling fluid with the copper nitrate is not corrosive (the corrosion rate was 0.00084 lb/ft2 after 24 h at 212 °F). Breakeven experiments showed that adding copper nitrate to the drilling fluid doubled the adsorption capacity when compared with triazine and tripled the capacity when compared with Scav1 when using I lb of the commercial H2S scavenger per bbl of the drilling fluid.