Innovative Oil Offloading System for Deep Water

Abstract

Offshore oil production with the employment of FPSOs (Floating, Production, Storage and Offloading) unit faces the challenge of increasing well volumes, processing and storage capacity and ultimately oil offloading and transportation. Following the natural activity development in some oil fields, the number of spread-moored FPSOs and the employment of Dynamic Positioning Shuttle Tankers increased, however represent altogether a bottleneck for the production capacity and considerable transportation cost increment. The need to implement alternatives for the use of larger and conventional tankers is evident, and several attempts and use of technology are being tested and proposed. The work presents preliminary numerical and cost analysis of an innovative Oil Loading Terminal (OLT) for deep water. Based on field data, metocean studies and extensive practical experience, the OLT should allow direct offloading from the FPSOs onto conventional shuttle tankers including VLCCs. The OLT concept allows the transfer of oil from an FPSO to a conventional tanker moored in CALM Buoy through submerged oil offloading lines (OOLs) supported by a tethered submerged buoy. The conventional tanker will receive the oil through a floating hose string. The cornerstone of this OLT concept is the subsurface buoy application to support the OLLs and consequently de-coupling the FPSO and CALM Buoy motions simultaneously. As a result, the OOLs loads and fatigue efforts under the CALM Buoy also decrease. The paper evaluates an OLT specific conception for the Brazilian offshore pre-salt area and results related to the numerical analysis carried out are presented considering one submerged buoy connected to a FPSO and CALM Buoy via flexible offloading lines respectively. The results appoint to a technically feasible solution that can be complementarily laboratory and field tested. Further, the solution cost impact has been assessed and initial figures demonstrate that the final testing, construction and installation of one system will need investment that cost a fraction of tanker lifting costs currently requiring Ship-to-Ship oil transfers. The economies assessed with the use of this innovative solution include total avoidance of Ship-to-Ship costs; cuts transportation cost per ton in up to 50% (fifty percent), eliminates offloading bottlenecks allowing better use of FPSO storage and plant processing capacity, and ultimately decreases the number of tanker offloading operations with considerable benefit to operational safety by reducing risk exposure.