The QAS thermal development is one of the most productive fields in the Sultanate of Oman. The field's fractured reservoir has got a gas cap within excess of 3% H2S which makes it PDO's riskiest asset to be attended by well engineering operations. This paper will introduce two of the most innovative design optimizations which were implemented for the first time: Semi-Flush 5.5" Steam Completion and 7" Steam Completion

The main challenges that were mapped out and tackled during the implementation were, the 7-production casing ID limitation and the gas cap procedures and mitigations (Known as Natih requirement). In order to overcome the above challenges, a detailed engineering design was carried out for the casing string, connections and the tubing hanger. This paper will explain the detailed engineering approach from design to execution. The main elements discussed are, the design aspects of the 7" and Semi-Flush 5.5" strings, the annulus fluid replacement for annulus pressure build and using retrievable seal bore packer with bore extension under total losses.

In the initial 2 trials for the 5.5" steam completion, steam capacity was increased by 50%. This design will be applied to the full remaining scope of 15 existing wells. Also, the 7" steam injection completion was trailed in 2 wells. As a result, extra steam injection capacity has been added to fleet by converting gassed out producers to steam injectors. The highlight of the project was that with the 7" injection tubing, the steam injection capacity increased significantly and eliminated the need of drilling 4 new steam injectors, marking a considerable cost saving to the company. Avoiding the need of drilling new injectors also reduced the HSE exposure that is associated with high-risk wells with a risk of encountering sour shallow gas. Also, eliminating the dynamic fill for the upper part of the completion reduced Natih type operations which in turn reduced HSE exposure for future workovers significantly.

The Semi-Flush tubular with premium connections were used for the first time in the steam application to accommodate the limited annulus clearance between the steam injection tubing and the production casing strings. As well, repurposing of legacy gassed-out oil producers to 7" steam injectors whereby the 7" thermal completion was run for the first time. Also, deployment of thermal Retrievable Seal bore Packers enables future interventions without exposure to the sour gas cap from a naturally fractured carbonate reservoir.

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