Saipem has awarded Ocean Installer a USD-50-million contract for installation of steel catenary lazy-wave risers, freestanding hybrid risers, and export pipelines for Petrobras' Iracema field and other projects in the Santos basin presalt area, offshore Brazil. The scope of work specifies a wide range of services including survey, metrology, installation-aid deployment/recovery, and precommissioning. Ocean Installer will use the construction support vessel Normand Clipper during these operations.
Agbami field is a deep-water field located offshore Nigeria. The oil production system is a complex intelligent production network that consists of 22 subsea production wells (19 wells are dual zone completion while 3 wells are single zone completion), 8 subsea manifolds, 8 infield subsea flowlines and 8 subsea flowlines/risers. A production network model for Agbami production network was built in GAP production modeling tool. The model consists of 41 inflow elements, 177 pipe elements, 68 chokes and 200 nodes with real-time pressure/temperature (P/T) measurements. Due to the large number of elements and P/T nodes in the model, it was very daunting to calibrate the model by unstructured manual tuning of the model calibration parameters. In fact, it takes several days to manually calibrate the whole production network. A structured computer assisted calibration workflow was developed to aid in fast calibration of the Agbami production model.
The structured approach to the Agbami production network model calibration used in this work is to first break down the model into 8 independent riser subsystems. Each riser subsystem is then further broken down into segments. The segments are zones, wells, infield flowlines, and flowlines/risers; with each segment having several elements and P/T nodes. Each segment of the model is independently calibrated using the latest production test data corresponding to that segment. A computer guided wizard was developed to sequentially match the P/T at different nodes of the segment using the Secant root-finding algorithm1. The calibrated segments are then coupled together into riser subsystems and each riser subsystem is then calibrated to the latest riser tests by manual adjustment of few parameters. The riser subsystems are further calibrated to the current conditions. The use of the structured computer assisted workflow has resulted in the faster model calibration time of within a day.
Rated for drilling-riser strings up to 500 tons, the elevator handles stress joints, riser joints with buoyancy cans, and riser joints with or without strakes and fairings. The nonmarking feature on the tool protects against stress- concentration factors created by standard dies, which extends the life of the riser joint. Hydraulic operation of the spider and elevator eliminates the time needed to manually bolt standard lifting gear, ultimately reducing overall run times. Used with Weatherford's integrated safety-interlock system, the elevator can be operated remotely to eliminate manual riser-running tasks and keep personnel out of hazardous zones.
AbstractDuring subsea mining operations, minerals are extracted from the seabed, typically at about 2000m depth, and pumped with water through a riser pipe to a surface processing vessel. TechnipFMC, through its subsidiary Technip France, is the lead of a consortium comprising COMEX and DCNS which has been awarded a contract by BPIFrance to develop a pilot subsea mining system. The scope includes the development of a flexible riser. This flexible riser comprises an inner wear protection layer to resist the wear from the slurry, covered by a structure to withstand mechanical loads applied to the flexible during its lifetime.In order to select the most appropriate anti-abrasion material, a large scale bench test has been built to reproduce realistic flow in a piping system and compare wear on different materials; rubber, polyethylene and stainless steels. Complete analysis of the wear patterns has been conducted with the expertise of a laboratory. A statistical comparison between materials is presented. The response to wear, depending on material, geometry and position, is better known. One of the materials shows much better wear resistance than the others and is selected for further development.The next step is the development and qualification of the manufacturing process for the wear protection layer. This process has to be as much as possible compatible with current flexible pipe manufacturing plant. Parameters such as thickness, diameter or length of the layer should be adaptable according to needs. The compatibility with the pipe mechanical structure has to be tested as well. To meet these requirements, existing manufacturing processes are limited. At the time of writing this paper, different manufacturing methods to incorporate this wear protection layer within a continuous industrial flexible production are currently under investigation. Several prototypes will be realized for each manufacturing step. Prototyping is under test and will be presented in a forthcoming presentation.
AbstractWellhead fatigue monitoring was performed during Plug and Abandonment (P&A) activities of a well in the Gulf of Mexico (GOM). Fatigue monitoring was deemed necessary for several reasons: an older vintage of wellhead system with uncertain fatigue life consumption from previous drilling activities, excessive wellhead stick-up, potentially large rig motions from a moored drilling rig for P&A. Fatigue monitoring was performed to ensure the integrity of the wellhead during P&A operations.The wellhead fatigue monitoring methods previously developed by several of the coauthors was applied in the wave-dominated GOM environment. Motions of the Blow Out Preventer(BOP) stack were measured and combined with a model of the riser/BOP/wellhead/casing system to reconstruct fatigue damage in the wellhead, conductor and surface casing. To measure wellhead motions, Subsea Vibration Data Loggers (SVDLs) were run with the riser and retrieved via Remotely Operated Vehicle (ROV). Fatigue damage reconstruction in the wellhead, conductor and surface casing was performed directly using the measured motion data and an analytical transfer functions obtained from the calibrated Finite Element (FE) model. Results were provided with fast turnaround time to support operations.Results demonstrated that fatigue damage rates compared well with pre-deployment predictions, though measured fatigue demand was slightly higher. It was also demonstrated that the primary cause of fatigue damage was due to wave activity at the site. Analysis of low frequency response at the riser natural frequencies indicated that the first few riser modes may have been excited by currents. It was also demonstrated that the low frequency response did not contribute significantly to fatigue life.The wellhead monitoring methods discussed result in rapid turn-around of valuable fatigue life consumption information, enabling informed decisions to be made in challenging conditions. The monitoring instrumentation and fatigue analysis methods increase the safety and efficiency of drilling, workover and P&A activities. In a larger sense, measured data also serves as a benchmark for analytical model calibration activities, reducing the known conservatism in stress and fatigue in future deployments.
Clukey, E. C. (Jukes Group) | Aubeny, C. P. (Texas AandM University) | Zakeri, A. (BP America Inc.) | Randolph, M. F. (University of Western Australia) | Sharma, P. P. (Det Norske Veritas) | White, D. J. (University of Western Australia) | Sancio, R. (Geosyntec Consultants Inc.) | Cerkovnik, M. (2HOffshore)
AbstractThe paper provides a review of the state of knowledge regarding the impact of soil response in the touchdown point region on Steel Catenary Riser (SCR) fatigue. For almost 20 years the impact of soil-pipe interaction on SCR fatigue has received considerable attention within the offshore geotechnical community. Over this course of time field measurements and a variety of experimental and analytical studies have been performed to determine the soil response necessary to characterize the soil-pipe interaction under long term loading conditions appropriate for fatigue. Little of this work has been integrated into existing codes and standards. This paper will summarize much of the new work to provide better insights on how to address the SCR fatigue problems and to serve as reference for future code modifications.
AbstractTypical subsea equipment design uses the widely industry-adopted stress design allowables of 2/3 × Yield, 80% × Yield, and 100% × Yield for normal, extreme, and survival load conditions, respectively. These factors are associated with current API product specifications based upon the ASME linear-elastic (LE) analysis approach and establish the customary relative design margins between the three load event categories. For high-pressure high-temperature (HPHT) and often thick-walled equipment, API17TR8 recommends the use of more advanced elastic-plastic (EP) stress analysis over LE techniques. This is because EP analysis utilizes the actual material constitutive response that more closely approximates the actual structural behavior, better represents the non-linear stress distribution across the component's wall, and models the redistribution of stress that occurs due to inelastic deformation. EP analysis relies on the concept of Load and Resistance Factor Design (LRFD) where the allowable service load(s) are determined by dividing the calculated collapse load by a factor to account for uncertainty and the resistance of the components to the load is thereby assessed. The ASME Section VIII Division 2 and Division 3 codes (hereinafter referred to as Div. 2 and Div. 3) currently only assign LRFD factors for normal load conditions and the applicability of these factors for the other types and magnitudes of loads in a subsea environment need further evaluation. There exists a need for the oil and gas industry to adopt verified and validated normal, extreme, and survival load factors for EP analysis that provide the same relative margins as the LE design allowables.The ASME EP verification analysis method assesses the acceptability of a component by evaluating several failure modes. The focus of this study is the global collapse failure mode that results from ductile rupture or gross deformation as a result of the applied loads. One of the benefits of the EP method is when a system is analyzed as a whole, consistent design margins are de facto applied to all components. Sound engineering practice dictates that whatever load factors used must be valid for simple geometries if they are expected to be applicable for complex assemblies. Analysis models and test specimens of simplified geometries were analyzed to collapse and tested to failure under combined loads so trends could be identified and established. The LRFD factors are applied to the calculated collapse loads from analysis and correlations are made to the validation tests to failure. The uncertainty of survivability when using the factors is also discussed realizing these design factors have been established for load events whose frequency of occurrence is based on risk assessment.Physical testing of 43 thick-walled test specimens to failure has been performed. Normal, extreme, and survival load capacities were calculated based on collapse from EP analysis using multiple material models and were compared to the loads at failure in the tested specimens. Probabilistic methods have been applied to assess the likelihood of failure using the various verification methods. This work would be beneficial for use by the industry standards' committees when considering the adoption of normal, extreme, and survival design factors.
AbstractFor the development of the new frontiers in Brazil, spread moored FPSOs with a large number of flexible risers connected to one board of the unit are considered. Due to the large water depth and severe environmental conditions, the design of the flexible risers is challenging and the roll motions of the FPSO are a key parameter. The roll motions may induce large vertical displacements at the top of the risers which affect the ultimate strength of the flexible pipe as well as fatigue of end- fittings. Moreover, the vertical motions and accelerations may induce compression of the riser which could lead to exceedance of allowable curvature limit. The common practice for estimation of FPSO roll motions is to consider the unit in the free floating condition, without the presence of mooring lines and risers. The resulting motions are then imposed at the top of the risers in a decoupled way. Ideally, a fully coupled analysis should be performed in time domain in order to take into account the dynamics of the floater and lines systems simultaneously as well as the nonlinearity involved. However, as this type of analysis is very time consuming, an alternative methodology is proposed, which enables to consider the effects of coupling at early design phase at a reasonable timeframe. This methodology consists in performing preliminary numerical tests (forced motions) in order to obtain the effects of additional stiffness, added inertia and damping originated by the mooring lines and risers to be included in a decoupled motion analysis in the frequency domain. In this study we consider the example of a spread moored system in deep water depth designed for operating in Brazilian conditions. In this case it is observed that the coupling effects are very important, mainly for intermediate and shallow drafts of the unit. In particular, the lines (mooring and risers) may significantly contribute to damp the roll motions. As a consequence, the top tensions in the flexible pipes would be lowered comparing to the results of usual decoupled analysis.
Moreira Matoso Ribeiro Gomes, F. (Petrobras S.A.) | Dal Pont, A. (Petrobras S.A.) | Maia Arantes, F. (Petrobras S.A.) | Cavalcanti Freitas, G. A. (Petrobras S.A.) | Rodrigues Marques, M. A. (Petrobras S.A.) | Souza Salvador, M. de (Petrobras S.A.) | Santos Poli, P. R. (Petrobras S.A.) | Oliveira, R. Caldeira de (Petrobras S.A.) | Laquini, S. (Petrobras S.A.) | Santos, T. Duarte Fonseca dos (Petrobras S.A.) | Gasparetto, V. (Petrobras S.A.)
AbstractThe Oil and Gas industry has faced an unpredictable and fast transformation in the last years. At first, there were barrel prices over U$ 100 dollars, which motivated a huge worldwide investment that pushed operators and the supply chain to respond to unprecedented growth. Due to the downturn in the oil prices, the challenge has moved towards achieving project feasibility in a low Brent scenario. The Brazilian subsea oil and gas industry has struggled with this context. Initially, with the Pre-Salt discoveries in 2006 it was necessary to develop breakthrough technological solutions to face this new frontier and to build 10 ultra deep-water production systems happen in just 10 years. Due to the recent price drop, Petrobras subsea engineering area has faced a demand to develop simpler and cost efficient solutions to reduce Pre-Salt CAPEX and OPEX.The objective of this paper is to review how Petrobras subsea area is dealing with these challenges since the discovery of Pre-Salt in 2006 until the current downturn of the oil and gas industry. As a reaction to that, Petrobras has been running an internal strategy called Subsea Cost Reduction Plan - PRCSub. The main purpose of this program is to search for the biggest cost reduction opportunities and to promote a full integration among Petrobras subsea team and suppliers.The PRCSub has delivered excellent results. Around US$ 500 million in savings were registered between 2014 and 2015 in the subsea scope, and between 25% of CAPEX reduction was achieved in Pre-Salt developments due to optimization initiatives for subsea design.The paper will present a review of the initiatives, describing the technical solutions and the new business model under construction by Petrobras.