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The objective of this paper is to provide a review of the evolution of the flow assurance discipline over the years as it applies to the design of gathering and export pipeline systems. In the early days, pipeline design was essentially a job for one engineer when pipelines were on land or in shallow water, not in a new geological province, flowing temperatures / pressures were not abnormal, and had no multi-phase flow or contaminants. This paper will identify events or circumstances that affected how "~Pipeline Hydraulics" were designed. Flow Assurance Engineering has evolved from two fundamental pillars – thermo-hydraulic analysis of fluid flow in production systems, and production chemistry. Today, flow assurance engineers in a project not only provide predictions, but also prevention strategies, and remediation methods for: Fluid characteristicsFlow hydraulics and thermal behaviorsPerformance of the production systemGuidance of operation strategiesIdentification and management of solid deposition issues: hydratesparaffins (waxes)asphaltenesscales, etc. They interface with multiple disciplines involved with the project, including subsurface, pipeline and risers, subsea hardware, topsides process facilities, chemical vendors, the fluid laboratory, etc. Beginning in the late 1940s, pipelines began transporting hydrocarbons over long distances onshore (conversion of the Big Inch Crude and Little Inch product pipelines to natural gas service for example) when unforeseen flow problems began to occur. Exploration gradually moved to nearshore drilling, and finally, to shallow water. Additional flow problems increased in complexity and magnitude. To track how these increasingly complex flow problems affected pipeline design, this paper presents: The evolution of Flow Assurance from simple hydraulics calculations to a well-defined engineering disciplineThe critical responsibilities in current deepwater development - Greenfield and Brownfield projectsThe re-shaping of Flow Assurance Engineering by digital revolution and big data technologiesThe evolution of the discipline applying new technologies to unlock new reserves with longer, deeper tiebacks

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Bottom tow pipeline bundle installations are gaining acceptance in deepwater developments. This is particularly the case where paraffins and hydrates pose a problem, since insulation and heating lines may easily be added inside the buoyancy casing, with less cost impact than in vessel based methods. However, barriers to more extensive use of the bottom towed bundle technique are perceived problems of potential leakage into the outer casing and perceived problems related to the pressurization of the casing. Approaches to mitigation of such problems, such as Bulk heading and foam filling are proposed and evaluated herein. Introduction Deepwater developments currently underway are increasingly requiring either insulation or heating to prevent hydrate formation or waxing in flowlines traversing cold ambient waters. Flowlines may be insulated either with directly applied insulation, pipe-in-pipe insulation, or insulation wraps within cased bundles. Heating may be achieved utilizing heating water in separate lines or annular jackets, or electrically, utilizing skin effect current transfer or other means. Possible installation methods, already in use or imminent, include reeling, J-lay, S-lay or towing of bundled pipelines. In a towed installation, the pipelines and casing are welded into strings on a beach. To date, all Gulf of Mexico bottom towed bundles have been fabricated at Matagorda Peninsula, just down the coast from the mouth of the Colorado River. Thus site accommodates bundles up to 10 miles long. The bundle is then deflected laterally off of the beach and towed to the site. Pipelines may be towed on the sea dace, at mid- depth, or on bottom. All the Gulf of Mexico bundled installations have been by bottom tow.@ The bundled approach to installation of multiple pipelines, is to gather the several pipelines into a single package, and to provide a casing around the entire package which brings the total bundle submerged weight into a desired range. For a bottom towed bundle this submerged weight must be great enough to provide stability during the launch and tow process but low enough to permit towing by available vessels. The casing diameter required for correct submerged weight is normally sufficiently large such that an insulating wrap layer may be added to the flowlines without change in the design of the bundle, and the low density of insulating materials makes only a modest change in the submerged weight. In shallow water depths the casing may resist hydrostatic collapse through its inherent stiffness, however, as water depths increase the increase in wall thickness required to prevent buckling makes it impossible to achieve a desired submerged weight.

Offshore pipeline design encompasses all types of pipelines: from waste water outfall lines that extend seaward for shore, continental shelf pipelines (0–600 ft or 200 m), oil and gas production pipelines, some of which terminate onshore, and others that end at another offshore facility; deepwater oil, gas, and water injection lines in depths from 600 ft/200 m out to 10,000 ft/3300 m; and ultradeep pipelines, 10,000 ft and deeper. Waste water outfall lines are excluded in this text as the design of these generally requires a different mindset for the designer. While a 48′‐diameter oil or gas pipeline is considered large, an outfall line may be 4 or 5 times larger, and is usually a concrete pipe. Steel pipe, in diameters between 4″ (102 mm) and 24″ (610 mm), will accommodate most of the deepwater pipeline scenarios likely to be encountered by the offshore pipeline designer. Steel pipe diameters up to 60″ (1524 mm) have been designed and used in shallower water, notably for tanker loading/discharge pipelines. Since the subject of this article is virtually limitless in depth, knowing what to cover and what to leave out was difficult. Many books would be required to completely cover all aspects of offshore pipeline systems. Some very good books have been written, recently at a somewhat accelerated pace, that are worth reading. Rather than including a précis of these books, technical papers, and articles published in trade journals, a reference list is included to help the reader investigate each topic beyond the presented scope. Regarding presentation, this article focuses on the engineering principles used for designing and optimizing offshore pipeline systems rather than in‐depth theories. Derivation of mathematical models is beyond the scope of this encyclopedia.