An offshore gas field uses a membrane acid gas removal unit (AGRU) to remove H2S from the sales gas and condensate stream to meet low specification and operate reliably. A stringent pre-treatment specification is a must to ensure reliability and integrity of the system. With high H2S concentration in condensate from the pre-treatment regeneration cycle, it is imperative to treat both gas and condensate stream to meet gas sales specification. This paper covers process engineering and flow assurance design implemented for gas and condensate H2S removal system and determining sour service operating envelope necessary for pipeline material selection utilizing multiphase transient simulation modelling.