bluuebunny/crossref_metadata_2025_split huggingface dataset:
An Integrated Sediment Mobility and Scour Assessment: Characterisation, Calibration and Mitigation Studies for a Pipeline in the South China Sea
Authors: O'Leary L. , Spinewine B. , Haneberg W. , Clare M. , Thomas S. , Wu H. 
Published: February 2015

We present an export pipeline case study in the South China Sea in water depths between 200 m and 600 m. Several types of sediment bedforms and variations in seabed roughness were identified at seafloor; hence the requirement for a sediment mobility assessment. Data types acquired include seafloor and sub-bottom geophysical data, geotechnical samples, in situ tests, geological analyses, hydrological testing and metocean measurements. The outcome of the testing determined sections of pipelines requiring burial.
A phased approach was taken from a qualitative, geomorphological assessment, to a quantitative determination of a morphological baseline. This approach is applicable to scour assessment for cable, pipeline routes and other seafloor structures and ensures that unnecessary effort is not wasted at early stages of assessment.
A review was initially performed of regional present day and past metocean regimes and a geomorphological assessment of features characteristic of sediment mobility. A geometrical characterisation identified the superposition of small, younger bedforms on megaripples. A targeted sampling programme acquired cores for detailed sedimentological and geochronological analysis to validate these interpretations. Critical shear stress values for mobility were determined from theoretical relationships (classical Shields curve) and from erosion function apparatus (EFA) testing performed in the laboratory on site-specific samples. The local sediment flow conditions were plotted on bedform regime diagrams for oceanic flows identifying that not all of the observed bedforms could be considered in equilibrium under present day near-bed current conditions. A predictive relationship for bedload sediment transport was used to assess sediment transport rates over the bedforms. An active bedform field was identified, with predicted migration rates of up to 1.8 m during one year extreme background conditions. This was mitigated by using a spectral decomposition approach to identify the amplitudes of mobile versus immobile bedforms and obtain probabilistic estimates of a morphological baseline.
Assessments of sediment mobility and scour need to be geologically credible, temporally relevant, and well calibrated. An assessment of sediment mobility from just one of the methods may provide either over- or under-conservative design solutions. This study demonstrates the importance of full integration and the added benefit of inputs from multiple different disciplines.
Two degrees of freedom CFD Simulation of Vortex Induced Vibration of Two Circular Cylinder in Tandem Arrangements
Authors: Jamei S. , Maimun A. , Ghazanfari S.A. , Tofa M. , Ahmed Y.M. 
Published: February 2015

Many researchers have studied on the flow around a steel riser for the vibration and fatigue analyses that are the principal challenges in riser design and fabrication. It is a demand to enhance our knowledge about vortex-induced vibration effects (VIV) on the risers in deep-water for oil extraction.
VIV is the main factor to predict the long life of the risers. In this study, the fatigue estimation of steel riser in deep water will be numerically investigated, and then design parametric study respect to some design parameter such as mass ratio and aspect ratio of riser will be done.
The motion of the riser and flow pattern around it will be examined in detail. This fluid structure interaction (FSI) problem will be solved by commercial code ANSYS. Reynolds-averaged Navier-Stokes equations (RANS) and some turbulent models will be employed in computational fluid dynamics (CFD) for force calculation and finite element (FM) method will be used for structural analysis. For validation purpose, the numerical results will be compared with other research works. Next, the effect of design parameter on vibration and fatigue life of steel riser will be explored.
Hopefully, new findings of the current study can be useful for riser research and design.
Improved Numerical Simulation for Shale Gas Reservoirs
Authors: Guo Chaohua , Wei Mingzhen , Chen Haowei , He Xiaoming , Bai Baojun 
Published: February 2015

Producing gas from shale strata has become an increasingly important factor to secure energy over recent years for the considerable volume of natural gas stored. Unlike conventional gas reservoirs, gas transports in shale reservoir is a complex process. In the organic nano pores, slippage effect, gas diffusion along the wall, viscous flow due to pressure gradient, and desorption from Kerogen coexist. In the micro fractures, there exists viscous flow and slippage. Also, with pressure depletion, gas viscosity will decrease. The porosity will increase when the gas desorbs from the pore wall. However, factors such as viscosity decrease and porosity increase have not received enough attention in existing mathematical models. It is important to construct a unified model considering all known mechanisms.
In this paper, based on dual porosity continuum media, mass balance equations in matrix and fracture were constructed using dusty gas model. In the matrix, Knudsen diffusion, Fick diffusion and viscous flow were considered. Gas desorption was characterized by Langmuir isothermal equation. In the fracture, Forchheimer flow was considered. Porosity increase was calculated by the equivalent volume increase due to gas desorption from the pore wall. Gas viscosity was characterized as a function of Knudsen number. Later, equivalent integral weak forms were derived based on constant pressure boundary. And model got solved using finite element method. Finally sensitive factors of shale gas production were analyzed. The results show that considering gas viscosity change increases cumulative gas production by nearly 12% under given reservoir conditions. Considering porosity increase will obtain higher production than without. The matrix and fracture permeability increase with time during production. Ignoring one of these factors such as Knudsen diffusion, slippage effect, desorption, viscosity decrease and porosity increase will obtain less cumulative production. For more accurate shale gas production prediction, it is crucial to incorporate these factors into the model.
Centrifuge Model Study on Vertical Pullout Behavior of Square Plate Anchors in Normally Consolidated Clay
Authors: Chen J. , Tho K.K. , Leung C.F. , Chow Y.K. 
Published: February 2015

As oil and gas extraction has reached increasingly deep water in recent years, floating platforms are now more widely used than conventional facilities. The mooring of floating systems can be problematic since significant vertical loading is imparted to the foundation systems. Consequently many different types of anchors have been developed to resist the pullout forces, and compared with conventional anchors SEPLA (suction embedded plate anchor) is more widely used because of its lower cost and shorter installation time.
The vertical uplift capacity of plate anchors has been studied extensively. However most of the studies were based on theoretical and numerical analysis or tests in 1g conditions. In the present paper, 50g and 100g centrifuge model tests are performed to analyze the pull-out behavior of plate anchors in normally consolidated soft clay and the soil flow mechanism during the uplift process.
The anchor is idealized as square in shape. Load-displacement curves and vertical pullout capacity are obtained in a series of wish-in-place tests. The contributing factors are also examined, with special attention paid on the anchor embedment ratio (H/B). Half-anchor tests are performed to study the soil movement patterns surrounding the anchor during the uplifting process, by using PIV (particle image velocity) method and the close range photogrammetry technique. Results are presented in the form of capacity factor (Nc) and are also compared with previous numerical and empirical solutions. Full-flow mechanism (soil flows around the anchor with local failure in shear) is observed in the half-anchor tests.
This study with centrifuge model test provides insightful information on the uplifting pullout capacity of plate anchors as a part of foundation systems of floating platforms, as well as the flow and failure mechanism of surrounding soil.
CO2 Removal from Natural Gas Using Membrane Contactor
Authors: Chan Zhe Phak , M Yusop Nurida , Abai Mahpuzah , M Shariff Shahidah , Ishak M Adaham 
Published: February 2015

CO2 is one of the major contaminants in natural gas streams. Its removal from the natural gas stream is necessary prior to entering downstream units of the gas processing plants due to Health, Safety and Environment (HSE) concern, heating value specification, as well as plant and pipeline corrosion issues. CO2 is conventionally removed using acid gas absorption tower and membrane technologies. Application of these technologies in offshore facilities requires high capital and operating expenses, and large foot print.
The potential reduction in both capital investment and equipment footprint has made membrane contactor technology a compelling solution for the removal of CO2 in natural gas. A membrane contactor is a device that allows gas-liquid mass transfer without direct contact of the two phases which flow at the different sides of the membrane. Recent findings have shown that membrane contactors have several advantages over those existing separation systems, which include smaller footprint, modular, not sensitive to flooding, channelling or back-mixing, and provide larger contact areas for increased mass transfer rate. Realizing its potential, PETRONAS and Dalian Institute of Chemical Physics (DICP) have successfully completed a development study on membrane contactor which can remove CO2 from feed gas containing a range of 70-10% of CO2 down to as low as 1% at the outlet gas stream. The technology could potentially further remove CO2 down to ppm level meeting LNG specifications. A pilot plant to demonstrate its performance on actual plant conditions will be commissioned at PETRONAS Gas Processing Plant in 2013.
Use of Platform Response Measurements from On-Line Monitoring (OLM) System to Verify the Effectiveness of Structural Repairs and Managing On-going Structural Integrity
Authors: Nichols N.W. , Md Harif H. 
Published: February 2015

Structural member damage to fixed-jacket offshore platform occurs for a number of reasons including impact damage from vessels and fatigue of ageing jackets. Such structures represent substantial capital assets to operators and therefore it is important to verify the effectiveness of structural repairs in restoring the structural integrity of the platform.
An On-line Monitoring (OLM) instrumentation system at deck level can be used to continuously monitor the structural response due to ambient from wave and on board sources before, during, and after the repair process.
The observed changes in structural response can be compared with those predicted using finite element structural analysis. The outcome from a Pilot study implementing the use of OLM by Petronas Carigali Sdn Bhd (PCSB) has enabled PCSB to effectively identify that the repair was adequate and further demonstrated the applicability for using OLM for Managing Structural Integrity over time in assessing the effectiveness of any future repairs.
The paper also describes details on demonstrating the benefits of using OLM in supporting the ongoing Managing of Structural Integrity due to degradation arising from various sources to assist engineers in making and verifying correct engineering assessment decisions and where appropriate supporting the case for either enhancing safety or reducing inspection/maintenance activities.
ECA of High Pressure and High Temperature (HP/ HT) CRA Pipelines
Authors: Kumar Shashi B. , Chong Steven , Tornqvist Rikard , Tronskar Jens P. , Lai Man On , Loh Wai Lam 
Published: February 2015

Deepwater and marginal oil and gas fields are often found to be at high pressure/ high temperature combined with high CO2 concentration in the production fluid. In order to develop the oil and gas fields with harsh environment, C-Mn line pipes is considered to uneconomical / nonviable and CRA Clad line pipes are increasingly selected for such situations. The CRA clad line pipe generally consists of C-Mn backing steel material with 3.0 mm (nominal wall thickness) metallurgically clad layer at the inner diameter made from nickel base alloys 825 or 625 or 316L stainless steel. Often small diameter line pipes (&lt; 10" diameter) is made by joining two (2) 6m pipes using 309 Mo consumables.
These line pipes are typically welded on board the lay barge using 622 or 625 nickel base or 2509 super duplex consumables. The recent research has shown that the tensile and fracture toughness properties which is most important to ensure the integrity of the girth welds is very sensitive to the test temperature, specimen geometry, specimen sampling direction. Moreover due to planned and unplanned lateral buckling design the girth welds may be subjected to high peak strain/stress, sometimes in the range of 0.5 to 1.5% total strain. Engineering critical assessment (ECA) performed according to DNV OS-F101 appendix A is used to derive the weld flaw acceptance criteria for inspection of girth welds by automatic ultrasonic testing (AUT).
There are several challenges associated with HP/HT CRA pipeline such as i) under-matching girth weld as compared to the base metal yield strength, especially at elevated temperatures, ii) small tolerable flaws which are difficult to achieve with practical girth welding procedures iii) high noise level vs. signal during inspection of the girth welds using automated ultrasonic testing due to anisotropic nature of austenitic or austenic/ferritic weldments and CRA layer. Often welding specification requires that no detectable imperfections are present in the root pass and possibly also in the hot pass. The paper l discusses the above mentioned challenges in relation to HP/HT CRA pipelines and provides some solutions and guidelines for ECA of CRA clad lines.
Implementation of a Trans-Horizon Microwave Troposcatter Communication Link
Authors: Jin Wong Hock , Zainudin Abi Sufyan , Khan Mohamad Rizal 
Published: February 2015

This paper discussed the implementation of a Trans-Horizon Microwave

Troposcatter
Communication Link between one of the Talisman Malaysia South China Sea offshore platforms and an onshore facility in Malaysia. This communication link replaces an existing VSAT (Very Small Aperture Terminal) system.
The platforms are located too far from any networked asset to be linked by Optical fiber or line-of-sight microwave. Apart from the high operating cost, the VSAT link has a minimum latency of 0.5 second due to the use of geo-stationary satellites and bandwidth is limited to only 4Mbits/sec. Studies have identified Digital Troposcatter as an industry proven technology offering higher data rate and minimal latency. This paper describes how the offshore platform will be used as a communication hub for the adjacent platforms.
Conventional Microwave links are impeded by the curvature of the earth, Troposcatter overcomes the earth's curvature by exploiting the natural scattering of radio signals that occurs in the low atmosphere. The scattered signal may be picked up by a high gain antenna and sensitive receiver. Digital signal processing is used to enhance the received signal and for the Troposcatter link to provide a 20Mbits/sec duplex data with Quality of Service in excess of 99.95%.
This requires the procurement and fabrication of high technology equipment, not commonly found in civilian installations, and the construction of transmitting and receiving facilities onshore and offshore.
The paper will discuss the project justification, the principles of the link and illustrate the design, procurement and engineering challenges.
25Cr Completion Campaign Successfully Meets Unusual, Highly Corrosive Reservoir Conditions - A Case History
Authors: M Noor Adlan Long , b Samad M Elmy Ismail , Osuji-Bells Godwin , b Khalid M Zaidan , Budi Setiawan Trigunadi , Rodhiah Siti , Zol Hamidy Hudzaifah , Paramavathar Sanggeetha , Madi Diana 
Published: February 2015

Gas wells often produce sour gas (H2S) along with significant quantities of CO2, and when it is suspected that these conditions will be encountered, corrosion-resistant alloys (CRAs) must be used in completions. This paper discusses an unusual development strategy for an offshore gas cluster off Peninsular Malaysia. The planning for the project had to consider that the environment contained approximately 57% CO2 in addition to H2S. To meet the needs of this project, a dedicated team from the operator and service/engineering company developed a completion strategy incorporating several "firsts" for this area. This paper will discuss the unusual completion strategies selected, why they were used, and the resulting success of the well completions. This was the first usage of 25Cr by this operator in Malaysia. Some of the changes included:Alloy 25Cr was used for all 3–1/2- and 4–1/2-in. completion equipmentThe equipment was rated for 5000psi and 7500psi
The wells were completed without any issues relating to the use of any of the new strategies, and these have become the standard for all future Monobore/Dual completion wells with high CO2 content and low H2S content for both upper and lower completions. The wells have been in operation for more than one year, and production has been as anticipated.
This case history covers the early stage planning (including materials recommendation stage), technical design review, equipment design, CRA handling and equipment preparation onshore, CRA handling offshore, and completion execution throughout the campaign. Results of the operation from a mechanical perspective will also be presented.
ANN Powered Virtual Well Testing
Authors: Aggarwal A. , Agarwal S. 
Published: February 2015

Abstract
Due to the drying up of old oil fields throughout the globe, the age of easy oil is over and the newly discovered fields have reservoirs with complex heterogeneous media. The reservoir parameters are identified indirectly by correctly interpreting well test model which is recognized by the feature of pressure derivative curves. Well testing involves creation of disturbance in fluid flow by injecting liquids and simultaneously recording the pressure transient data. Lost production, equipment and personnel costs turn well testing as highly cost intensive job making it difficult to cover all the important wells in a particular field. But with the advent of artificial neural networks (ANN) it is now possible to generate synthetic pressure transient data. This technique provides a basis to leach out detailed information from the available pressure transient data and it doesn't eradicate the need for actual well tests. This technique can also prove to be very vital in cases where equipment breakdown may have taken place and full set of data couldn't be availed. This simulated well testing involves training of a neural network from pressure transient data obtained from designated wells in the field, which has the potential to generate pressure transient responses at other well sites where no well test has been conducted.
In this paper a 3 layer multi-layer perceptron (MLP) Time Delay Neural Network - NARX model has been designed working on resilient backpopagation algorithm for training. Cubic Spline Interpolation has been used from enriching the data before feeding it to NARX model. A simulated example which highlights the efficiency of NARX model in attaining accurate synthetic pressure transient data has been discussed. The neural network is successful in predicting well test interpretation model. The ANN thus produces expeditious and reliable synthetic data which has the potential to revamp the industry.
Managing Micro-Emulsion and Scale During ASP Flooding for North Sabah Field EOR
Authors: Alwi Noraliza , Borhan Noorazlenawati , B M Ibrahim Jamal Mohamad , Paramanathan Subashini , Bouwmeester Ron 
Published: February 2015

Alkaline Surfactant Polymer (ASP) flooding has been identified as one of the best EOR methods to further recover the trapped oil in Malaysian maturing fields. ASP flooding application promises a huge incremental recovery factor based on recent successful implementation on offshore fields in other part of the world. The application of ASP flooding has been identified for pilot in North Sabah reservoir which is currently flooded with seawater since March 2011. Despite the promising recovery factor from the pilot laboratory and simulation study with incremental recovery of &gt;80% above waterflood, the ASP flooding success always comes with risks and challenges.
Two major challenges behind the success of ASP flooding are the formation of scales near wellbore due to the high pH of the alkaline in the injection fluid and the tight micro-emulsion which produced back in separator vessel which contains surfactant breakthrough. The identified pilot North Sabah reservoir which is currently been flooded with seawater is expected to further worsen the scaling effect due to the high divalent cation concentration (i.e. Ca2+ and Mg2+) in seawater. In addition, the high seawater cut causes a very tight micro-emulsion which is very difficult to manage. These challenges cause formation damage which impact injectivity and flow assurance issue to the production facilities as well as impair the crude quality and sellability.
This paper will discuss in great detail on the lab test results which was designed based on the reservoir simulation ASP flooding study in North Sabah reservoir. Based on the in-situ produced water and chemical breakthrough simulated, this paper describes the extent of emulsion and scale severity at various ASP to water ratio, extensive performance tests evaluating the demulsifier and the scale inhibitor and discusses on the challenges in finding the suitable demulsifier and scale inhibitor at the simulated breakthrough condition.