Amirhossein Molayee - Iranian Offshore Oilfield Company, SPE

The majority of the wells which have been drilled in Iranian offshore oilfield in Persian golf include a build and tangent section in 8 ½ hole section, landing the well at same section and drill a 6 ⅛ horizontal section through reservoir. Most of these wells have been drilled by the conventional steerable mud motor assemblies.In Foroozan oilfield in Persian golf due to presence of famous Ahmadi and Nahr Umr formation which has unstable shale lithology, steerable motor is relatively inefficient process with associated problem.To provide directional control in build and tangent section, considerable oriented drilling has been required. Oriented drilling has proved to be time consuming and would often result in poor borehole quality. On top of this, slow ROP and bit hanging up during sliding are other factor which impact drilling performance.In order to minimize the effect of these issues, rotary steerable system has been deployed in one well in Foroozan oilfield in Persian golf for 8 ½ section drilling by Iranian Offshore Oil Co. over the past year.This paper looks at a range of specific applications where the change from steerable motor to rotary steerable system has been both technically and commercially successful in offshore Foroozan oilfield. Through the case history, this paper will demonstrate both tangible and intangible benefits resulting from the use of rotary steerable systems that have led to a step change in overall drilling performance