diameter) above the mudline, which is used to mount a Christmas tree (control panel with valves). diameter) is a topside structure of the drilling casing (typically 36-in. įlowline Connection Figure 1.1.1 Subsea System.Subsea System The subsea system can be broken into three parts as follows: Dry trees are useful for top tension risers (TTRs) or fixed platform risers and provide reliable well control system, low workover cost, and better maintenance. Wet trees are commonly used for subsea tiebacks using long flowlines to save cycle time (sanction to first production). If the wellhead is located on the seafloor, it is called a wet tree if the wellhead is located on the surface structure, it is called a dry tree. įigure 1.2 Offshore Field Development Components.Each element (system) is briefly described in the following sub-sections. 6Offshore field development normally requires four elements as below and as shown in Figure 1.2. Figure 1.1 Worldwide Deepwater Exploration and Production The deepwater exploration and production (E&P) is currently very active in West Africa which occupies approximately 40% of the world E&P (see Figure 1.1). By the year 2005, Statoil’s Kristin Field in Norway holds the HP/HT record of 3,212 psi (911 bar) and 333oF (167oC), in 1,066 ft of water. Currently, subsea systems of 15,000 psi and 350oF (177oC) have been developed. The deepwater flowlines are getting high pressures and high temperatures (HP/HT). The longest oil subsea tieback flowline length is 43.4 miles (69.8 km) from the Shell’s Penguin A-E and the longest gas subsea tieback flowline length is 74.6 miles (120 km) of Norsk Hydro’s Ormen Lange, by 2006. The deepest flowline installed is 2,743 m (9,000 ft) in the Gulf of Mexico (GOM). Improved geology survey and E&P technologiesĪ total of 175,000 km (108,740 mi.) or 4.4 times of the earth’s circumference of subsea pipelines have been installed. More investment cost (>~20 times) but more returns Relatively larger (~20 times (oil) and 8 times (gas)) offshore reservoirs than onshore Limited onshore gas/oil sources (reservoirs) Deepwater developments outrun the onshore and shallow water field developments. INTRODUCTION Deepwater means water depths greater than 1,000 ft or 305 m by US MMS (Minerals Management Service) definition. PIPELINE PROTECTION – TRENCHING AND BURIAL. Even though the exact sources are quoted and listed in the references, please use this note for engineering education purposes only. It should be noted that some pictures and contents are borrowed from other companies’ websites and brochures. Unlike other text books, many pictures and illustrations are enclosed in this note to assist the readers’ understanding. Readers are encouraged to refer to the references listed at the end of each section for more information. The author’s nearly twenty years of experience on offshore pipelines and risers along with the enthusiasm to share his knowledge have aided the preparation of this note.
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PREFACE This lecture note is prepared to introduce how to design and install offshore petroleum pipelines and risers including terminologies, general requirements, key considerations, etc. Introduction to Offshore Pipelines and Risers