The agreement for the asset sale was signed in August 2018.
The FCA assets are located in San Juan and Rio Arriba counties in New Mexico, as well as La Plata, Colorado. The assets include 3,700 miles (5,954km) of pipeline, two gas processing facilities, and a carbon dioxide treatment facility.
Williams is a natural gas processing and transportation firm, while Harvest Midstream Company is a midstream service provider that is an affiliate of Hilcorp Energy. Both firms are based in the US.
The sale proceeds will be used for capital growth and investment.
Shell CAPSA has sold its downstream business located in Argentina to Raízen for $916m.