This paper presents experience and best practice for a new geotechnical laboratory test protocol – the low stress interface shear box (ISB) test – for determining soil properties relevant to pipeline-seabed friction. The paper is underpinned by a major database (>200 tests) that demonstrates the protocol and shows general variations in the key parameters that may be useful for early design purposes. By accurately quantifying shear resistance along the pipe-soil interface under low normal stresses imposed by subsea pipelines, ISB tests allow design ranges in axial friction to be narrowed and tailored to specific pipeline conditions. These improved geotechnical inputs to pipe-soil interaction can alleviate unnecessary axial expansion, walking or buckling mitigation, unlocking cost savings otherwise unavailable without accurate geotechnical parameter characterization.
A large database is presented of recent industry experience with low normal stress interface shear testing using a modified direct shear box device. This device, while still considered novel, is emerging as the new industry standard for axial pipe-soil interaction testing, gaining wider adoption than the tilt table and torsional shear devices. The test database comprises several soft clays from various deep water hydrocarbon-producing geographical regions, and several types of pipeline coatings.
The database populates a theoretical framework for axial pipe-soil interaction with new data, illustrating general trends for key parameters such as shearing duration, normal stress, interface roughness, and changing pipeline weight, each of which is shown to vary the axial resistance by a factor of two or more. The shear resistance can also change by a factor of two or more due to consolidation or swelling during and between individual cycles of movement, associated with pipeline operations. This database and the populated theoretical framework can guide pipeline and geotechnical engineering by providing a basis for initial estimates of axial friction, and an approach for improving these estimates via focused site-specific testing.
The new approach has been applied through >200 ISB tests for >12 oil and gas projects conducted in the laboratories of Fugro and the University of Western Australia, to deliver better pipe-soil interaction data than is available via other means. This paper shares this experience to support new projects in two ways: Firstly, the large high quality database provides a significantly improved basis for estimates of geotechnical soil properties for subsea pipeline design where site-specific data is not yet available. Secondly, we provide guidance on the planning, execution and interpretation of low stress interface shear tests, to allow best practices to be adopted more widely across industry.
An analytical methodology for estimating walking anchor force is presented. Currently, anchor force calculation requires substantial FEA which is not compatible with early phase design schedules. At such stage, anchor force is typically assumed to correspond to full pipeline length mobilization. This is very conservative, in many cases by an order of magnitude, and can hence mislead important early design decisions.
The force on a walking anchor increases with cycles of pipeline operation, eventually approaching an asymptotic limit value, often of the order of 1 MN. Robustly identifying this limit requires extensive FEA, incorporating detailed bathymetry, simulating tens to hundreds of operational cycles, and covering numerous sensitivities to input parameters, which often yield counterintuitive results. The proposed analytical method does not require repetitive calculations. It derives the limit value straightforwardly, based on fundamental principles, and has been implemented in a spreadsheet.
Providing immediate results, it permits quick assessment of the effects of many parameters such as soil resistance, operating loads, as well as the number and location of global buckles, on the system's ultimate response. Results are shown to agree very well with extensive FEA results, and yield required anchor loads which are much lower than the full-length mobilization approach. Having such results early in design allows better informed decisions, for example making end anchors viable, and thus avoiding much more complicated mid-line ones. Pipeline ends can be anchored by either adopting piled foundations or by connecting them to a separate anchor pile. Mid-line anchors mobilize lower loads, however in most cases require additional attachments or structures, which bring additional concerns in terms of through-life integrity, and installation cost, safety and schedule risks.
The proposed tool permits proper estimation of anchor loads at early design stages, and can make otherwise too expensive concepts viable. Its capability of quickly assessing multiple sensitivity cases also allows early identification of the relevant aspects to be tackled later in the project, in a value engineering approach.
Thiagarajan, K. P. (University of Massachusetts Amherst) | Lackner, M. (University of Massachusetts Amherst) | Manwell, J. F. (University of Massachusetts Amherst) | Breger, D. (University of Massachusetts Amherst) | Arwade, S. R. (University of Massachusetts Amherst) | Myers, A. (Northeastern University) | Hajjar, J. (Northeastern University) | Courtney, F. (Tufts University) | Hines, E. (Tufts University) | Niezrecki, C. (University of Massachusetts Lowell) | Kirincich, A. (Woods Hole Oceanographic Institution) | Lohrenz, S. (University of Massachusetts Dartmouth) | Cash, D. (University of Massachusetts Boston)
In order for our nation to develop its vast offshore wind resource in a manner that respects the ocean environment and its many stakeholders, it is critical that we develop a coordinated, long-term strategic vision for advancing American innovation in this new industry. This vision is particularly relevant to the Commonwealth of Massachusetts, which has, inter alia, set a target of 25% of its electricity needs supplied by renewable sources by 2030. In accordance with this goal the Commonwealth has also mandated that 1600 MW of offshore wind be installed by 2027. This has been followed by opening up of three leases in federal waters off Massachusetts, selected with the help of the Bureau of Ocean Energy Management. The Massachusetts Research Partnership (MRP) in Offshore Wind, launched with seed funds from the Massachusetts Clean Energy Center's Renewable Energy Trust, includes six Massachusetts academic and research institutions - Northeastern University, Tufts University, UMass Amherst, UMass Dartmouth, UMass Lowell and Woods Hole Oceanographic Institution. The goal of the MRP is to develop a data driven multi-disciplinary system level framework for offshore wind research needed to galvanize academia, industry, stakeholders, and policy makers in order to create a resilient, low-risk, productive, and world-leading offshore wind infrastructure and portfolio of wind farms. The MRP was established to prepare a national research agenda that will align the efforts of federal, state, and other entities that share a vision for offshore wind, and suggest how stakeholders can collectively work together to further develop and support an effective national research program. The Wind Energy Center and the Clean Energy Extension program at the University of Massachusetts at Amherst have active education and research programs in the area of offshore wind. With the support of the MRP workshops on Development of a National Offshore Wind Research Agenda were held during 2016 – 17. These workshops mobilized key players in the New England area and beyond and set the stage for further collaboration. Working closely with the National Renewable Energy Laboratory and other institutions, the Partnership for Offshore Wind Energy Research (POWER-US) initiative was recently formed. POWER-US will develop national collaboration that will accelerate the growth of the nascent offshore wind industry in the US. This paper will talk about the initiatives that are currently in progress in the Commonwealth of Massachusetts, including findings from the MRP workshops on Development of a National Offshore Wind Energy Research Agenda, and ongoing research and development initiatives that support development of the supply chain for the offshore wind industry in the Commonwealth and in New England.
Kim, CN (Hyundai Heavy Industry) | Hwang, HW (Hyundai Heavy Industry) | Kim, SE (Hyundai Heavy Industry) | Park, SM (Hyundai Heavy Industry) | Park, JS (Hyundai Heavy Industry) | Kim, TJ (Hyundai Heavy Industry) | Kim, YR (Hyundai Heavy Industry) | Kim, YH (Hyundai Heavy Industry)
Offshore development project are facing significant challenges from current market environment. Due to current low price of oil and gas, the development of natural reservoirs on offshore may not be attractive. However, the demand of natural gas will gradually increase because natural gas is relatively clean source comparing to the other fossil fuels and the demand of clean energy is growing due to environmental change.
In this regards, Near Shore FLNG is becoming one of the most economical solutions as the unit is equipped with essential liquefaction process, storage as well as offloading facility. That is, comparing to typical deepwater FLNG application, expensive components are not required such as the turret, complex pre-treatment system and self-generation of utilities, plus logistics such as refrigerant supply are better.
The purpose of this paper is to introduce the optimized process of Nearshore FLNG system comparing typical FLNG. To illustrate the optimized process, at first, target area is defined as North America. The reason why North America is selected is because of the potential of future projects and shale gas revolution. The gas composition is defined by reviewing 1,200 shale gas reservoirs in North America and considering the hydrocarbon gas is typical pipeline gas which needs to meet Pipeline Gas Spec requirement. Topside process is reviewed to find optimized options and process model has been built to check feasibility. Analysis is made on several technical optimized options as below.
Optimized Liquefaction system
Optimized Condensate System
Remove Deethanizer and Ethane make up column
Optimized Heating Medium system
Optimized Produced Water Treatment System
Finally, this paper provides several options with reducing several facilities and optimizing process which will reduce CAPEX/OPEX.
The broader implications of changing offshore pipeline survey methodology to reduce cost and improve accuracy are also covered.
Shi, Hongfu (China National Offshore Oil Company) | Luo, Xianbo (China National Offshore Oil Company) | He, Yifan (China National Offshore Oil Company) | Chen, Cunliang (China National Offshore Oil Company) | Re, Bo (The University of Texas at Austin)
D oil field located at the west of Bohai Bay of China is characterized as a complex fluvial reservoir with multiple oil-water systems. It is classified as a marginal field because of the thin sand channels (average 12m), low oil columns(less than 10m), strong bottom aquifer, and high oil viscosity (30-300mPa.s). In order to drive the project forward, several solutions were present in the process of ODP (Overall Development Plan) implementation.(1) The PDS (progressive development strategy) which meant limited well to develop large reserves by sidetrack frequently was present to short payback period under the low oil price condition.(2) We accurately anatomized the sand architecture in four levels, including compound channel, single channel, point bar, and lateral accretion body with high-quality seismic data and guided by the high resolution sequence stratigraphy. After these work, a large 3D visualization of geological reservoir model was set up to quantitative the potential and risk.(3) Horizontal wells were widely used to delay bottom water coning and maximize initial productivity. A brand new equation about the swept volume of horizontal wells was proposed to determine the well spacing. Smart wells were drilled based on the accurate description of interlayer.(4) In the program of horizontal well drilling, the study team must overcome the challenges in identifying the oil water contact (OWC) while placing the trajectory within a very small target window close to the roof. A detailed technology review, advance azimuthal LWD, with the ability to map the distance to the multiple boundaries such as the OWC, the top and bottom of the reservoir structure in the remaining oil column, was selected as the fit-for-purpose application and to enhance reservoir understanding.
We present a multi-resolution probabilistic ocean forecasting system designed to support offshore energy operations worldwide. The system is composed of an integrated suite of ocean circulation models including a global model of 25 km resolution, Atlantic and Indian Ocean models of 6 km resolution, and 8 fine scale models (< 3 km resolution) for high-priority regions such as the Gulf of Mexico, offshore Brazil, West Africa, and the Caribbean. It expands on current ocean prediction systems through exclusive access to proprietary data streams, state-of-the-art data assimilation methods and ensemble modeling capabilities. The global and basin scale models incorporate large-scale information from satellite and in-situ observations and provide initial and boundary conditions for the regional models. The regional scale models then dynamically downscale the initial and boundary conditions to produce both deterministic and probabilistic fine-scale forecasts for regions of interest.
The system has been validated for consistency, quality, and accuracy against a suite of publicly available models and field observations (Remotely sensed observations, ARGO float data and Drifting Buoys). Results show that the system compares favorably to other leading ocean current forecasting systems such as HYCOM and the Mercator system. Experiments in the Gulf of Mexico demonstrate that the fine-scale forecasts are further improved by using proprietary data streams and when operated in an ensemble (probabilistic) mode they also provide robust quantification of uncertainty in forecasts.
The system has been operational since the beginning of 2017, providing daily 7-day forecasts of ocean currents. Additionally, 20-year hindcasts for some regions are in progress and outputs will be available for extreme value analysis for planning and structural design. It is expected that Ocean current hindcasts and forecasts through the new system will translate to increased situational awareness, reduced downtime, improved environmental protection, and safety.
Pankaj, Piyush (Schlumberger) | Geetan, Steve (EP Energy Corporation) | MacDonald, Richard (EP Energy Corporation) | Shukla, Priyavrat (Schlumberger) | Sharma, Abhishek (Schlumberger) | Menasria, Samir (Schlumberger) | Xue, Han (Schlumberger) | Judd, Tobias (Schlumberger)
In today's data-driven economy, operators that integrate vast stores of fundamental reservoir and production data with the highperformance predictive analytics solutions can emerge as winners in the contest of maximizing estimated ultimate recovery (EUR). The scope of this study is to demonstrate a new workflow coupling earth sciences with data analytics to operationalize well completion optimization. The workflow aims to build a robust predictive model that allows users to perform sensitivity analysis on completion designs within a few hours.
Current workflows for well completion and production optimization in unconventional reservoirs require extensive earth modeling, fracture simulation, and production simulations. With considerable effort and wide scale of sensitivity, studies could enable optimized well completion design parameters such as optimal cluster spacing, optimal proppant loading, optimal well spacing, etc. Yet, today, less than 5% of the wells fractured in North America are designed using advanced simulation due to the required level of data, skillset, and long computing times. Breaking these limitations through parallel fracture and reservoir simulations in the cloud and combining such simulation with data analytics and artificial intelligence algorithms helped in the development of a powerful solution that creates models for fast, yet effective, completion design.
The approach was executed on Eagle Ford wells as a case study in 2016. Over 2000 data points were collected with completion sensitivity performed on a multithreaded cluster environment on these wells. Advanced machine learning and data mining algorithms of data analytics such as random forest, gradient boost, linear regression, etc. were applied on the data points to create a proxy model for the fracturing and numerical production simulator. With the gradient boost technique, over 90% accuracy was achieved between the proxy model and the actual results. Hence, the proxy model could predict the wellbore productivity accurately for any given change in completion design. The operators now had a much simpler model, which served as a plug-and-play tool for the completion engineers to evaluate the impact of changes in completion parameters on the future well performance and making fast-tracked economic decisions almost in real time. The approach can be replicated for varying geological and geomechanical properties as operations move from pad to pad. Although the need for heavy computing resource, simulation skillset, and long run times was eliminated with this new approach, regular QA/QC of the model through manual simulations makes the process more robust and reliable.
The methodology provides an integrated approach to bridge the traditional reservoir understanding and simulation approach to the new big data approach to create proxies, which allows operators to make quicker decisions for completion optimization. The technique presented in this paper can be extended for other domains of wellsite operations such as well drilling, artificial lift, etc. and help operators evaluate the most economical scenario in close to real time.
Potts, Andrew (AMOG Consulting) | Kurts, Phil (AMOG Consulting Inc) | Jayasinghe, Kanishka (AMOG Consulting) | Kilner, Andrew (AMOG Consulting Inc) | Melchers, Rob (University of Newcastle) | Lee, Tim (AMOG Consulting) | Chaplin, Richard (University of Reading)
Operators have, in the past, experienced high rates of corrosion for mooring systems in warm waters above those allowed for in traditional design guidance. The Joint Industry Project (JIP) for Seawater Corrosion of wire Rope and mooring Chain (SCORCH) was carried out with the participation of over twenty five offshore platform operators, equipment manufacturers, regulators and classification societies to address gaps in industry knowledge on the corrosion of steel wire rope and mooring chain, particularly in tropical waters.
The five-year project involved a broad range of research from literature review through to field experiments, examination of recovered in-service components and derivation of generalised corrosion models. Coupons of several grades of chain were deployed for a two year period at a number of sites to account for variation in temperature, oxygenation, current/wave action and water quality. Full-size chain links and lengths of smaller chain were also deployed for comparison, with special laboratory tests to investigate the effect of nutrient content on microbiologically influenced corrosion (MIC). Wire rope tests were carried out for a similar variation of environmental conditions as the chain tests. A range of specimens including individual wire strands, and wire rope sections with varying levels of blocking compound, jacketing and galvanic protection were subject to exposure for a period of three years and 6 months.
An extensive industry-wide survey of in-service and retired mooring components was also carried out to supplement these experiments. A standardised procedure for corrosion inspection was distributed to participants and a database of detailed wire rope and chain corrosion measurements was collated from approximately 30 floating production units (FPUs) operating in tropical waters in Asia, Africa and the Americas. Some recovered specimens were subject to more extensive examination, including 3D laser scanning and tensile break tests.
The SCORCH JIP advanced knowledge in the field of mooring corrosion by providing guidance on inspection and integrity management methodologies, unique insight into the factors affecting the corrosion performance of steel wire rope and mooring chain, and generalised predictive corrosion models for the assessment of mooring corrosion. These recommendations are presented in the following paper.