The companies have been among the main beneficiaries of difficulties created for Iran's oil and gas sector by the US-led international sanctions of recent years.
A huge demand for onshore and offshore rigs has fuelled massive investment by private companies and by the existing state drillers in new rigs from abroad and from Iranian manufacturers.
Last month's sailaway of the jack-up Aban VIII from its Sembawang yard in Singapore to the site of the South Pars Phase 12 development illustrated Iran's continuing, even if somewhat limited, ability to charter rigs from abroad.
