f Tender Assist Drilling (TAD)

Platform rig is an immobile offshore structure from which development wells are drilled and produced. The degree of a platform rig has an important effect in the field development cost. In offshore, development wells can be drilled by a giant platform rig that can also has production and processing facilities as well as living accommodations for the people. Alternatively, these functions may be conducted on different platforms that are much smaller than a giant platform. This can be achieved by using Tender Assist Drilling (TAD) which has a split drilling unit. The unit that is immobile is a fixed platform and the other unit is mobile that provides logistic to fixed platform. TAD system requires employing a Tender Support Vessel (TVS) during the drilling phase of a well development to provide drilling utilities to the platform drilling equipment package. In the first years of the TAD’s, barges mainly were used as tender to fixed platforms in shallow water and good weather conditions but, it was seen that they easily became inoperable and unsafe in deep water and rough weather. Alternatively, in 1980’s, the use of the tender assist barges in harsh weather, existing mobile offshore drilling units (MODU), Semi-submersible platforms, were converted to Semi-Submersible tender for fixed platform. This study aims to review tender assist drilling (TAD) and its applications in the world. Besides, my goal particularly is to present an application of tender assist drilling performed by Turkish Petroleum Corporation (TPAO) in Turkey. TPAO constructed a fixed platform in Akçakoca Natural Gas Development Field, Düzce and a tender assist barge was chosen for that fixed platform.