H2S Risk Management Plan For A Semi-Submersible Drilling Rig

Hydrogen Sulphide (H2S) is one of the main hazards involved with Oil and Gas operations, posing significant risks to people and assets. In the past years, due to the limited availability of deep water rigs, operators often found themselves with limited choices when procuring drilling rigs. This meant that sometimes the operator had to intervene to upgrade the rig to meet the specific company needs. This paper presents the activities carried out to prepare a conventional semi-submersible rig for an exploration drilling campaign on HP/HT wells with an estimated H2S concentration up to 6%. The significance of the expected H2S concentrations, the intrinsic uncertainty of the exploration wells and the typical constraints of an offshore environment required a comprehensive approach that goes beyond the design envelope and the normal operating modes of conventional rigs. As a result, different measures were developed together with the rig contractor, targeting rig equipments, operating procedures, training and awareness of the personnel. This paper aims at disseminating the process followed, the protection principles adopted and the cost-effective solutions implemented, whose validity is general and can be extended to similar contexts