Northstar Development Pipelines Limit State Design and Experimental Program

2000 ◽  
Author(s):  
André C. Nogueira ◽  
Glenn A. Lanan ◽  
Tom M. Even ◽  
Joe R. Fowler ◽  
Brett A. Hormberg
Keyword(s):  
Limit State ◽  
Experimental Program ◽  
Offshore Pipelines ◽  
Limit State Design ◽  
The North ◽  
Ice Surface ◽  
Offshore Pipeline ◽  
North Slope Of Alaska ◽  
Pipeline Welding ◽  
Prudhoe Bay

BP Exploration (Alaska) Inc. (BPXA) and its Northstar Project Alliance contractors started field construction of the Northstar development in January 2000 (Lanan et al. 2000). In April 2000, the offshore section of the Northstar pipeline reached Seal Island, located in 11 m water depth Northwest of Prudhoe Bay. Seal Island is in the Beaufort Sea, 9.7 km offshore from the shore crossing at Point Storkersen, on the North Slope of Alaska. Design, testing and permitting activities required multiple years leading up to this first of it kind pipeline construction project. Figure 1 shows the offshore pipeline welding spread working on the floating sea ice surface, similar to the conventional procedures used on the overland portion of the Northstar pipeline. This paper presents the limit state design of the offshore pipelines and the associated full-scale experimental program, which demonstrated that the pipelines can safely withstand operational bending strains up to 1.8%.

Evaluation of the Effect of Yield to Tensile (Y/T) Ratio on the Structural Integrity of Offshore Pipeline by Limit State Design Approach

2006 ◽  
Author(s):  
Gianluca Mannucci ◽  
Giuliano Malatesta ◽  
Giuseppe Demofonti ◽  
Marco Tivelli ◽  
Hector Quintanilla ◽  
...  
Keyword(s):  
Structural Reliability ◽  
Failure Modes ◽  
Structural Integrity ◽  
Limit State ◽  
Minor Effect ◽  
Offshore Pipelines ◽  
Limit State Design ◽  
A Minor ◽  
Probabilistic Failure Analysis ◽  
Failure Probabilities

Nowadays specifications require strict Yield to Tensile ratio limitation, nevertheless a fully accepted engineering assessment of its influence on pipeline integrity is still lacking. Probabilistic analysis based on structural reliability approach (Limit State Design, LSD) aimed at quantifying the yield to tensile strength ratio (Y/T) influence on failure probabilities of offshore pipelines was made. In particular, Tenaris seamless pipe data were used as input for the probabilistic failure analysis. The LSD approach has been applied to two actual deepwater design cases that have been on purpose selected, and the most relevant failure modes have been considered. Main result of the work is that the quantitative effect of the Y/T ratio on failure probabilities of a deepwater pipeline resulted not so big as expected; it has a minor effect, especially when Y only governs failure modes.

scholarly journals Rational Modeling of Ultimate Pipe Strength Under Bending and External Pressure

2000 ◽  
Author(s):  
André C. Nogueira ◽  
Glenn A. Lanan
Keyword(s):  
Deep Water ◽  
Limit State ◽  
Local Buckling ◽  
External Pressure ◽  
Pressure Effects ◽  
Combined Loading ◽  
Empirical Prediction ◽  
Limit State Design ◽  
Controlled Conditions ◽  
Offshore Pipeline

The capacity of pipelines to resist collapse or local buckling under a combination of external pressure and bending moment is a major aspect of offshore pipeline design. The importance of this loading combination increases as oil and gas projects in ultra deep-water, beyond 2,000-m water depths, are becoming reality. The industry is now accepting, and codes are explicitly incorporating, limit state design concepts such as the distinction between load controlled and displacement controlled conditions. Thus, deep-water pipeline installation and limit state design procedures are increasing the need to understand fundamental principles of offshore pipeline performance. Design codes, such as API 1111 (1999) or DNV (1996, 2000), present equations that quantify pipeline capacities under combined loading in offshore pipelines. However, these equations are based on empirical data fitting, with or without reliability considerations. Palmer (1994) pointed out that “it is surprising to discover that theoretical prediction [of tubular members under combined loading] has lagged behind empirical prediction, and that many of the formula have no real theoretical backup beyond dimensional analysis.” This paper addresses the ultimate strength of pipelines under combined bending and external pressure, especially for diameter-to-thickness ratios, D/t, less than 40, which are typically used for deep water applications. The model is original and has a rational basis. It includes considerations of ovalization, anisotropy (such as those caused by the UOE pipe fabrication process), load controlled, and displaced controlled conditions. First, plastic analysis is reviewed, then pipe local buckling under pure bending is analyzed and used to develop the strength model. Load controlled and displacement controlled conditions are a natural consequence of the formulation, as well as cross section ovalization. Secondly, external pressure effects are addressed. Model predictions compare very favorably to experimental collapse test results.

Off-shore oil and gas developments in Alaska: impacts and conflicts

Polar Record ◽  
1974 ◽  
Vol 17 (108) ◽  
pp. 255-275 ◽  
Author(s):  
George Rogers
Keyword(s):  
Construction Projects ◽  
Oil And Gas ◽  
Gulf Of Alaska ◽  
The United States ◽  
Gas Production ◽  
The Arctic ◽  
The North ◽  
North Slope Of Alaska ◽  
Arctic Coast ◽  
Prudhoe Bay

After three years' delay, work started early in 1974 on the construction of the trans-Alaska pipeline from Prudhoe Bay on the Arctic coast of Alaska 1 270 km to Valdez on the Gulf of Alaska (Ronhovde. 1974). Within three years, the line should be delivering 1.2 million barrels per day, a volume that will be increased eventually to a daily flow of 2 million barrels. Gas production on the North Slope of Alaska will probably be exported through Canada to the United States through a 4 184-km pipeline that will cost an estimated $5.7 billion and, if built, will be one of the largest construction projects ever undertaken; the system will also carry Canadian Arctic gas to southern markets. The size of these projects is in themselves impressive, and they have been spawned and are being launched in an atmosphere of controversy and confusion that, in its different way, is equally impressive.

Dispersive noise removal in t-x space: Application to Arctic data

Geophysics ◽  
1988 ◽  
Vol 53 (3) ◽  
pp. 346-358 ◽  
Author(s):  
Greg Beresford‐Smith ◽  
Rolf N. Rango
Keyword(s):  
Signal To Noise Ratio ◽  
Noise Analysis ◽  
Noise Removal ◽  
North Slope ◽  
Frequency Bandwidth ◽  
The North ◽  
North Slope Of Alaska ◽  
Seismic Records ◽  
Time Offset ◽  
Undersampled Data

Strongly dispersive noise from surface waves can be attenuated on seismic records by Flexfil, a new prestack process which uses wavelet spreading rather than velocity as the criterion for noise discrimination. The process comprises three steps: trace‐by‐trace compression to collapse the noise to a narrow fan in time‐offset (t-x) space; muting of the noise in this narrow fan; and inverse compression to recompress the reflection signals. The process will work on spatially undersampled data. The compression is accomplished by a frequency‐domain, linear operator which is independent of trace offset. This operator is the basis of a robust method of dispersion estimation. A flexural ice wave occurs on data recorded on floating ice in the near offshore of the North Slope of Alaska. It is both highly dispersed and of broad frequency bandwidth. Application of Flexfil to these data can increase the signal‐to‐noise ratio up to 20 dB. A noise analysis obtained from a microspread record is ideal to use for dispersion estimation. Production seismic records can also be used for dispersion estimation, with less accurate results. The method applied to field data examples from Alaska demonstrates significant improvement in data quality, especially in the shallow section.

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