Interference of Top Tensioned Risers for Tension Leg Platforms

2017 ◽  
Author(s):  
Hanqing Zhang ◽  
Derek Smith
Keyword(s):  
Production Systems ◽  
Selection Process ◽  
Combined Effects ◽  
Direct Impact ◽  
Interference Analysis ◽  
Field Development ◽  
Strong Current ◽  
Induced Velocity ◽  
Oscillating Motion ◽  
Wave Induced

Dry tree top-tensioned risers (TTRs) are widely used on floating production systems such as TLPs and Spars for drilling, completion, workover and production. The interference between neighboring TTRs is an important consideration which has a direct impact on the total TTR payload budget and the wellbay size for floater sizing and cost. Since the realistic sizing of a floater is essential towards the concept selection process for a field development, TTR interference should be addressed at the early stages of an offshore oilfield development. If the floater is a tension leg platform (TLP) and the field has strong current with associated extreme waves, riser interference may be very challenging and can have direct impact on riser design and the sizing and layout of the TLP. The waves and the oscillating motions of the TLP will have effects on riser interference. The oscillating motion of the TLP can excite the vibrational motion of the risers, and the wave-induced velocity of water particles and the motions of the risers with the movement of the TLP increases the relative flow acting on each riser. The combined effects will increase the deflection of the risers and thus the likelihood of riser interference. The industry has not seen an acceptable interference analysis approach yet which can account for the combined effects of current, waves, and TLP motions. This paper proposes two engineering approaches for the interference analysis of top tensioned risers for tension leg platforms with the combined effects of current, surface waves, and associated floater motions being addressed.

Entrepreneurial selection and use of legal counsel

2007 ◽  
Vol 10 (2) ◽  
pp. 59-63 ◽  
Author(s):  
Stephen J. Schanz
Keyword(s):  
Cash Flow ◽  
Selection Process ◽  
New Ventures ◽  
Legal Issues ◽  
Financial Resources ◽  
Legal Services ◽  
Careful Attention ◽  
Direct Impact ◽  
Legal Counsel

Entrepreneurs starting new ventures will encounter a host of legal issues requiring consultation with an attorney on an episodic or ongoing basis. It is critical that careful attention be given to the attorney selection process to properly match the needs of the company with the credentials of the attorney.Additionally, options should be explored regarding the billing and payment methodologies the attorney is willing to entertain. The financial resources and cash flow of young companies will likely have a direct impact on the financial agreements entered into with legal counsel. Further, companies desirous of offering the attorney a stake in the company as full or partial payment for legal services need to be mindful of ethical restrictions applicable to the lawyer, as well as exceptions to the lawyerʼs malpractice coverage arising from his or her role with the company

scholarly journals ADCP Bias and Stokes Drift in AUV-Based Velocity Measurements

2017 ◽  
Vol 34 (9) ◽  
pp. 2029-2042 ◽  
Author(s):  
André Amador ◽  
Sergio Jaramillo ◽  
Geno Pawlak
Keyword(s):  
Wave Field ◽  
Field Experiments ◽  
Autonomous Underwater Vehicle ◽  
Stokes Drift ◽  
Linear Wave ◽  
Velocity Measurements ◽  
Adcp Measurements ◽  
Local Wave ◽  
Induced Velocity ◽  
Wave Induced

AbstractA theoretical model is developed to describe how autonomous underwater vehicle (AUV)-based current measurements are influenced by a surface wave field. The model quantifies a quasi-Lagrangian, wave-induced velocity bias as a function of the local wave conditions, and the vehicle’s depth and velocity using a first-order expansion of the linear wave solution. The theoretical bias is verified via field experiments carried out off the coast of Oahu, Hawaii. Spatially averaged along- and cross-track AUV velocity measurements are calculated over one effective wavelength and compared with time-averaged, fixed ADCP measurements in a range of wave and current conditions. The wave-induced bias is calculated using wave directional spectra derived from fixed ADCP data. Ensemble-averaged velocity differences confirm the presence of the wave-induced bias O(1–5) cm s−1 and reveal an additional bias in the direction of the vehicle motion O(1) cm s−1. The analysis considers velocity measurements made using a Remote Environmental Monitoring Units (REMUS) 100 AUV, but the content applies to any small AUV (vehicle size wavelength) immersed in a wave field.

scholarly journals Wind‐wave‐induced velocity in ATI SAR ocean surface currents: First experimental evidence from an airborne campaign

2016 ◽  
Vol 121 (3) ◽  
pp. 1640-1653 ◽  
Author(s):  
Adrien C. H. Martin ◽  
Christine Gommenginger ◽  
Jose Marquez ◽  
Sam Doody ◽  
Victor Navarro ◽  
...  
Keyword(s):  
Experimental Evidence ◽  
Wind Wave ◽  
Ocean Surface ◽  
Surface Currents ◽  
Ocean Surface Currents ◽  
Induced Velocity ◽  
Wave Induced

Design Considerations of a Subsea Shuttle Tanker System for Liquid Carbon Dioxide Transportation

2020 ◽  
Author(s):  
Yihan Xing ◽  
Muk Chen Ong ◽  
Tor Hemmingsen ◽  
Kjell Einar Ellingsen ◽  
Lorents Reinås
Keyword(s):  
Carbon Dioxide ◽  
Production Systems ◽  
Electrical Power ◽  
Weather Conditions ◽  
Co2 Injection ◽  
Field Development ◽  
Design Considerations ◽  
Liquid Co2 ◽  
Carbon Dioxide Co2 ◽  
Subsea Pipelines

Abstract Subsea pipelines and umbilicals are used for the transportation of fluids and electrical power between subsea installations and floating production systems (FPUs). The installation and maintenance of these systems can be expensive. In a conventional subsea field development, the produced fluids can be transported from the well to a FPU where they can be offloaded to a tanker (surface ship). In the case of carbon dioxide (CO2) injection into the well, the direction of flow is reversed, i.e., CO2 flows from the tanker to the FPU, down the riser base and through the subsea pipelines to the well. This offloading process is weather-dependent and cannot be performed in severe weather conditions, i.e., strong winds and large waves. This paper presents a novel subsea shuttle tanker system proposed by Equinor ASA designed to be a possible alternative to subsea pipelines, umbilicals and tanker ships. The subsea shuttle is intended to operate submerged under the sea surface to transport liquid CO2 from an existing offshore/land facility where CO2 is captured to a subsea well where the CO2 is injected into the reservoir. As the shuttle is subsea, it can operate under any type of weather conditions. Even though the subsea shuttle is proposed as a vehicle for liquid CO2 transport, it can also transport other types of cargo such as hydrocarbons, injection fluids, electrical power or subsea tools. The paper will discuss the most important design considerations surrounding the subsea shuttle tanker.

Offshore concept field development

2015 ◽  
Vol 55 (2) ◽  
pp. 454
Author(s):  
Greg Saunders ◽  
Matthew Poole
Keyword(s):  
Management Strategy ◽  
Selection Process ◽  
Final Solution ◽  
Concept Selection ◽  
Field Development ◽  
Subsequent Investigation ◽  
Design Perspective ◽  
Technical Study ◽  
Development Concept ◽  
Selection Phase

This extended abstract describes the field development concept selection process for Karoon Gas Australia, as part of the appraisal and commercialisation of an oil resource in offshore Brazil. From an engineering design perspective, the concept selection phase offers the greatest opportunity to create project value. Options must be carefully considered before rigorous investigation to provide a firm foundation for key decisions. The concept selection study and option consideration began with a two-day framing and option identification workshop. Nine key decisions were identified as having significant impact on the feasibility and cost of the development. These included the wellhead type, hydrate management strategy, floating production storage and offloading vessel (FPSO) capacity, FPSO location, mooring type, subsea architecture, product export and expansion provisions. Assessment criteria were agreed on for each of the key technical decisions; these were applied in the evaluation of options defined. This workshop facilitated definition and agreement for the technical study scope. The subsequent investigation and selection process focused on the key development decisions that needed to be made immediately, compared to those that could be made at a later stage of the development. These decisions encompassed technical viability, dry trees versus wet trees, flow assurance, mooring type and processing capacity. A geologically complex reservoir drove many elements of the development selection process. This extended abstract highlights that the final solution balances risk management with maximising project value. The recommended base development concept is analogous to many developments already implemented in Brazil and is flexible enough to accommodate a realistic range of outcomes from future appraisal wells.

Metocean Design Criteria for Pipeline On-Bottom Stability

2011 ◽  
Author(s):  
Richard Gibson
Keyword(s):  
Parametric Representation ◽  
Extreme Value Analysis ◽  
Design Criteria ◽  
Value Analysis ◽  
Reliability Method ◽  
Extreme Response ◽  
Wave Cycle ◽  
Induced Velocity ◽  
Pipeline Design ◽  
Wave Induced

This paper is concerned with a response based method for determining metocean design criteria for offshore pipelines. The method determines a set of metocean parameters that are consistent with the extreme response of the pipeline, and hence, incorporates the dependence between them implicitly. However, there are a number of challenges in its application. Firstly, the loading on a pipeline is dependent on the previous wave cycle, and hence, the drag and inertia coefficients vary within a sea-state. Secondly, along many pipeline routes the waves are depth limited and the short-term distribution of wave induced velocity and pipeline response can be difficult to define. These challenges are overcome through a number of approaches that include a parametric representation of the distribution of the response and the application of multivariate extreme value analysis. Furthermore, the sensitivity of the method to assumptions about the pipeline design is examined, and the problems with using the combined wave and current induced velocity as a proxy for the response are discussed. The method is applied to a site in the Mediterranean Sea and the results are compared to those from the application of the first order reliability method.

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