Abstract

Hydrogen sulfide is naturally occurring gas that can be found in gas reservoirs, dissolved in hydrocarbon, water, or even liquid Sulphur. H2S can also be produced by microbiological processes, for example the reduction of sulfates by anaerobic bacteria such as sulfate reducing bacteria (SRBs). The existence of hydrogen sulfide even at low concentration yielded in localized corrosion and cause stress cracking. In addition, H2S causes damage to the pipes, valves and surface equipment.

Hydrogen sulfide is naturally occurring gas that can be found in gas reservoirs, dissolved in hydrocarbon, water, or even liquid Sulphur. H2S can also be produced by microbiological processes, for example the reduction of sulfates by anaerobic bacteria such as sulfate reducing bacteria (SRBs). The existence of hydrogen sulfide even at low concentration yielded in localized corrosion and cause stress cracking. In addition, H2S causes damage to the pipes, valves and surface equipment.

The objective of this study is to assess the using of copper nitrate as a catalyst for drilling fluids that can be used in drilling sour horizontal and multilaterals reservoirs. In addition, the effect of copper nitrate in rheological properties and the corrosion rate of the pipe will be evaluated.

The obtained results showed that adding copper nitrate with 1lb/bbl for the drilling fluid enhanced the rheological properties and H2S scavenging. The yield point/plastic viscosity ratio was increased by 20% without affecting the stress-strain behavior of the drilling fluid. The corrosion rate of the drilling fluid with the copper nitrate was very small (0.00060 lb/ft2 after 6 hrs) and (0.00084 lb/ft2 after 24 hrs) at 100°C. The standard corrosion (H2S + CO2, N2) test of the developed formulation showed that the corrosion rate was 0.00077 lb/ft2 after 6 hrs at 100°C. Breakeven experiments for base fluid, fluid with conventional Triazine scavenger, and the developed fluid showed that the drilling fluid with copper nitrate has three times the sorption capacity to H2S as compared to the drilling fluid with Triazine. The sorption capacity of the drilling fluid with copper nitrate is 5143 mg H2S/ml fluid, while that of both Bases and Base with Triazine fluids are 503 mg H2S/ml and 1666 mg H2S/ml, respectively.

The developed technique for H2S scavenging is very cheap and non-corrosive and will help the drilling engineer to drill multilateral and deep horizontal wells with safe and environmentally friendly method.

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