The joint venture of Abu Dhabi National Oil Company (Adnoc) and Occidental Petroleum Adnoc Sour Gas, formerly known as Abu Dhabi Gas Development Company (Al Hosn Gas), has issued prequalification documents for two packages that form part of the $2.3bn project to build a sour gas facility at the Shah field.

One package is for the gas plant itself, and is estimated to be worth $2bn.

The deadline for the submission of prequalification documents for this package is 26 October, according to industry sources.

The scope of this package includes a new gas sweetening train, central refrigeration unit, a solvent regeneration train, an oxygen plant and other associated facilities.

The other package is for gas gathering and gas export pipelines. The scope of the package includes three wellpads, pipelines, three gas gathering trunklines, a sales gas export line and associated facilities.

The gas gathering trunklines will have a diameter of 24 inches and will extend for 27km, from wellpads in the Shah field to the Shah gas processing plant.

The export pipeline will have a diameter of 36 inches and will extend for 128km, from the Shah gas processing plant to the Habshan gas plant.

In July, Adnoc said is was considering the investment of $20bn in developing sour gas reserves at up to five offshore fields, the state-owned group revealed in a company update.

Adnoc completed its first major sour gas project at the Shah onshore field in 2016 and is looking at options to expand capacity at Shah as well as several other fields.

Sour gas contains significant amounts of hydrogen sulphide which must be removed before the gas is used, making sour gas projects often more expensive and complex to carry out.