Using the Kriging Response Surface Method for the Estimation of Failure Values of Carbon-Fibre-Epoxy Subsea Composite Flowlines under the Influence of Stochastic Processes

This paper investigates the use of the Kriging response surface method to estimate failure values in carbon-fibre-epoxy composite flow-lines under the influence of stochastic processes. A case study of a 125 mm flow-line was investigated. The maximum stress, Tsai-Wu and Hashin failure criteria was used to assess the burst design under combined loading with axial forces, torsion and bending moments. An extensive set of measured values was generated using Monte Carlo simulation and used as the base case population to which the results from the response surfaces was compared. The response surfaces were evaluated in detail in their ability to reproduce the statistical moments, probability and cumulative distributions and failure values at low probabilities of failure. In addition, the optimisation of the response surface calculation was investigated in terms of reducing the number of input parameters and size of the response surface. Finally, a decision chart that can be used to build a response surface to calculate failures in a carbon fibre-epoxy-composite (CFEC) flow-line was proposed based on the findings obtained. The results show that the response surface method is suitable and can calculate failure values close to that calculated using a large set of measured values. The results from this paper provide an analytical framework for identifying the principal design parameters, response surface generation, and failure prediction for CFEC flow-lines.

Contrasting surface velocities between lake- and land-terminating glaciers in the Himalayan region

Meltwater from Himalayan glaciers sustains the flow of rivers such as the Ganges and Brahmaputra on which over half a billion people depend for day-to-day needs. Upstream areas are likely to be affected substantially by climate change, and changes in the magnitude and timing of meltwater supply are expected to occur in coming decades. About 10 % of the Himalayan glacier population terminates into proglacial lakes, and such lake-terminating glaciers are known to exhibit higher-than-average total mass losses. However, relatively little is known about the mechanisms driving exacerbated ice loss from lake-terminating glaciers in the Himalaya. Here we examine a composite (2017–2019) glacier surface velocity dataset, derived from Sentinel 2 imagery, covering central and eastern Himalayan glaciers larger than 3 km2. We find that centre flow line velocities of lake-terminating glaciers (N = 70; umedian: 18.83 m yr−1; IQR – interquartile range – uncertainty estimate: 18.55–19.06 m yr−1) are on average more than double those of land-terminating glaciers (N = 249; umedian: 8.24 m yr−1; IQR uncertainty estimate: 8.17–8.35 m yr−1) and show substantially more heterogeneity than land-terminating glaciers around glacier termini. We attribute this large heterogeneity to the varying influence of lakes on glacier dynamics, resulting in differential rates of dynamic thinning, which causes about half of the lake-terminating glacier population to accelerate towards the glacier termini. Numerical ice-flow model experiments show that changes in the force balance at the glacier termini are likely to play a key role in accelerating the glacier flow at the front, with variations in basal friction only being of modest importance. The expansion of current glacial lakes and the formation of new meltwater bodies will influence the dynamics of an increasing number of Himalayan glaciers in the future, and these factors should be carefully considered in regional projections.

Reservoir Monitoring Activities for Co2 Wag Pilots

Two CO2 WAG Pilots are in progress in an Abu Dhabi Oil Reservoir. Each pilot has one horizontal producer and two horizontal injectors along with 2 vertical pilot observers to monitor the movement of flood front away from the injectors. The pilots are being monitored based on a detailed reservoir-monitoring plan. The paper discusses in detail various activities and the results related to the pilot monitoring. Methods, Procedures, Process The wells are being tested for oil rate, water cut, GOR on a daily basis using MPFM. For calibration purposes portable test separators are used every quarter to validate the rate, water cut and GOR measurements. Separator PVT samples from pilot wells are collected every quarter for PVT analysis. In addition PVT samples are also collected from the pilot wells and nearby wells every month from the sampling point near MPFM to monitor the CO2 content in the produced gas. Online CO2 analyzer is fitted on the surface flow line connecting pilot wells to the RDS to provide continuous measurement of CO2 in the produced fluid. Produced water is also sampled for detailed compositional analysis. Different gas and water tracers have been injected through the pilot injectors to trace the movement and breakthrough of injected fluids into the pilot producers. Sampling and analysis for tracer is carried out on a regular basis. Carbon and oxygen Isotope analysis for produced and injected CO2 gas is also carried out in order to monitor the breakthrough of injected CO2 into the pilot producers. There is a good difference in the carbon and oxygen isotopes of injected CO2 and the CO2 present in the reservoir. To monitor the changes in water and gas saturation with time across different layers a set of Pulsed neutron (RAS) logs are run in the observers on regular basis. PLT logs are run in the injectors and producers to check the distribution and conformance of the produced and injected fluids along the horizontal wellbore. Walk away VSP surveys are being carried out on regular intervals for one pilot to monitor the injected fluids distribution in the pilot area. The paper describes all these reservoir monitoring activities in detail. Results, Observations, Conclusions Analysis of Carbon oxygen RST logs are helpful for tracking fluid saturation changes and CO2 movement across the logged intervals. The RST logs in the observers demonstrate good sweep across different layers of the reservoir. Analysis of CO2 in produced gas has resulted into correctly pointing out the timing of CO2 breakthrough in the producers. It is well supported by the CO2 isotopes analysis for the injected and produced CO2 through pilot producer and nearly producers. The tracer analysis results show clearly the injector from where the injected CO2 has reached the producers. The PLT logs demonstrate good conformance for CO2 and water injection across the horizontal section in the injectors. All these monitoring activities provide a good source of data for further analysis and improved understanding of the pilots. Novel/Additive Information The paper discusses the usefulness of different reservoir monitoring tools for improved understanding of the pilots, which will be used as a basis for implementing CO2 WAG for the full area development.

Integrated Project Management Approach for Production Well Tie-In in Upstream Projects-Case Study

Al Dhafra Petroleum Operations Company Limited, (Joint Venture between ADNOC and KADOC, established in late 2013 and assigned with Onshore and Offshore concession areas in Abu Dhabi) had the challenging task to achieve the sustainability of crude production to 40,000 BOPD by end of 2020 from their Haliba field. Current production profile with available wells could not meet that target, for which additional 4 production well Tie-in and construction of 8 km 6″ flow line became necessary within next 3 months. Regular Tie-in program may complete the first Tie-in only by Q2, 2021 and no possibility of enhancing this Tie-in works by 2020. Al Dhafra Management has appointed the Project Management Team (PMT) to take up the challenge by attempting many methods and the timeline was very limited (approximately 90days) to obtain First Oil from those wells.

Well Automation Based on Flaring

At a subsurface level, controlling uneven production and early gas breakthrough are big challenges. It is very difficult to achieve the target production while preventing unnecessary flaring from high gas to oil ratio (GOR) wells. To keep the associated gas within surface compression capacity, the High GOR wells are shut in or partially choked by production programmers through a manual work-process, which doesn't always give optimum results. PDO developed a control solution to ensure produced gas always remains within surface compression capacity while ensuring maximum production. The solution achieves this by continuously monitoring flaring and choking the high GOR wells whenever needed. It does this sequentially from highest to lowest GOR wells choking is done to an optimum level by controlling its flow line pressure above certain target. The concept revolves around automating production programmer's task and optimizing it via continuous monitoring and control in DCS, which allows wells to deliver the full potential up to the surface facility constraints with reduced operator intervention. This novel idea is to integrate subsurface and surface facility Optimization via well control. This was implemented in two of the assets in PDO where frequent flaring was identified. Both facilities have limited compression capacity and number of high GOR wells out of several Gas Oil Gravity Drainage (GOGD) producer wells. In order to achieve the goal of "Zero" flaring, the wells are choked in order from highest to lowest GOR, automatically, up to the optimum limit set by either their respective flow line pressures or to defined lower optimum limit, and optimize the production by opening the wells up to its optimum target, when there is no flare. The similar concept is now being replicated in other assets following a LEAN approach.

Micro-features of ambipolar snapback behaviour under high current injection to design capacitorless memory device

This paper presents micro-features of capacitorless memory cells based on snapback phenomenon and modeling of space-charges. 2—Dimensional gate grounded NMOS structure is specified and its operational window of the memory cell is inspected using the Synopsys TCAD tool. This work examines snapback behaviour in one transistor DRAM memory cell in the absence of a storage capacitor under zero gate bias and applied ramp of high current at the drain terminal. Carrier electrostatics and memory cell mechanisms are also explored by adjusting the slope of the high current ramp. The process variation is examined for different parameters in the device. The current crowding phenomenon due to the injection of electrons and holes is investigated, giving rise to ambipolar behaviour. Due to the snapback, redistribution of electron and hole current is investigated. This work also evaluates the impact on electrostatic potential along channel and bulk under the snapback. It explains the dependency of snapback on potential build-up. Post-snapback electron current flipping presents the flow line near the gate region. The bipolar activity is manifested in surface and bulk regions to show its impact through analytics. The effect of gate biasing is also examined under the applied current ramp.

Physical Modeling of Snow Gliding: A Case Study in the NW Italian Alps

Snow gliding, a slow movement downhill of snow cover, is complex to forecast and model and yet is extremely important, because it drives snowpack dynamics in the pre-avalanching phase. Despite recent interest in this process and the development of some studies therein, this phenomenon is poorly understood and represents a major point of uncertainty for avalanche forecasting. This study presents a data-driven, physically based, time-dependent 1D model, Poli-Glide, able to predict the slow movement of snowpacks along a flow line at the daily scale. The objective of the work was to create a useful snow gliding model, requiring few, relatively easily available input data, by (i) modeling snowpack evolution from measured precipitation and air temperature, (ii) evaluating the rate and extent of movement of the snowpack in the gliding phase, and (iii) assessing fracture (i.e., avalanching) timing. Such a model could be then used to provide hazard assessment in areas subject to gliding, thereby, and subsequent avalanching. To do so, some simplifying assumptions were introduced, namely that (i) negligible traction stress occurs within soil, (ii) water percolation into snow occurs at a fixed rate, and (iii) the micro topography of soil is schematized according to a sinusoidal function in the absence of soil erosion. The proposed model was then applied to the “Torrent des Marais-Mont de La Saxe” site in Aosta Valley, monitored during the winters of 2010 and 2011, featuring different weather conditions. The results showed an acceptable capacity of the model to reproduce snowpack deformation patterns and the final snowpack’s displacement. Correlation analysis based upon observed glide rates further confirmed dependence against the chosen variables, thus witnessing the goodness of the model. The results could be a valuable starting point for future research aimed at including more complex parameterizations of the different processes that affect gliding.

Application of physical theory of cavity in the construction of double skin facades

The article deals with the issue of double skin transparent facades as a new technological-operational system of transparent exterior walls. Especially of high-rise buildings, which with its operating modes ingeniously uses a renewable source of solar energy to reduce the energy needs of the building. The basic precondition for the correct function of the double skin facade is its functional aerodynamics in any climatic conditions of the outdoor climate. In the critical state of windlessness, the aerodynamic quantification of a double skin facade is the total aerodynamic resistance of the cavity, which consists of the aerodynamic frictional resistances along the length of the air flow line and local aerodynamic resistances of the cavity. The article analyses the functional aerodynamics on two frequented types of double skin facades with a narrow type and corridor type cavity. At the end it confronts functional aerodynamics with the results of their temperature, aerodynamic and energy regime obtained from in-situ experiments.