bluuebunny/crossref_metadata_2025_split huggingface dataset:
Design of Gelled Fluid for Debris Removal in Subsea Pipeline
Authors: Misra Chaitali , Danait Achala , Salgaonkar Lalit 
Published: March 2015

Summary
Transportation of hydrocarbon through a pipeline may be hindered as a result of deposition of debris. The presence of debris within the pipeline leads to reduction in the effective flow area, thus reducing the efficiency of the transportation system. Some of the factors leading to formation of the debris are changes in temperature and/or pressure of the transported fluid and chemical reactions, which occur therein.
Pipeline-maintenance pigging is performed routinely to extend the operational life of pipelines. Recently, a combination of mechanical and chemical remedial measures has shown beneficial results in pipeline cleaning. Mechanical-brush pigs loosen the debris adhering to the walls, while chemical techniques, such as the use of gelled fluids, enhance the carrying capacity and help to transport the loosened debris out of the pipeline.
This paper presents the results of tests conducted to design a fast-breaking gelled fluid for a debris-removal operation in a long, large-diameter subsea pipeline in the Asia Pacific region. In addition to exhibiting good stability and debris-carrying capacity under the laboratory test and field conditions, the gel had to be compatible and demonstrate stability when mixed with other additives in the transported hydrocarbon. A highly viscous, aqueous-based linear polysaccharide gel was designed to satisfy these requirements. A key environmental and operational consideration was the easy and fast disposal of the gel after completion of the cleaning operation. With oxidizing breaker, gels prepared in potable water resulted in viscosity of &lt; 10 cp within 2 days, which was significantly shorter than when seawater-based gels were treated similarly. Preliminary field results indicate that the combined mechanical and gel system removed a significant amount of debris. Data from future trials will help evaluate the feasibility of such a technique for effective cleaning of the pipeline.
Flare Gas Recovery in Tunisia--From Liability to Value
Authors: Bauer Matthias , Köck Mario , Jörg Klaus , Ramakrishnan Chandrasekhar , Mestiri Yassine , Scheed Andreas 
Published: March 2015

Summary
Thyna Petroleum Services (TPS) is a Tunisian joint-venture corporation of the Tunisian governmental oil and gas company, Entreprise Tunisienne d'Activités Pétrolières (ETAP), and the Austrian oil and gas affiliated group OMV A.G. based in Sfax. One of the future objectives of TPS is to avoid, or at least reduce, flaring of associated gas contained in crude oil during oil production. A particular challenge is to discover a process that enables the use of the associated gas despite its untypical gas composition for valorization processes.
Use of the associated gas will also reduce greenhouse-gas emissions. Therefore, this project also could be considered as a Clean Development Mechanism (CDM) project (United Nations 2010).
CDM is an arrangement under the Kyoto Protocol that allows industrialized countries with an emission-reduction or emission-limitation commitment to invest in an emission-reduction project in developing countries as an alternative to more-expensive emission reductions in their own countries. Such projects can earn saleable certified-emission-reduction (CER) credits, each equivalent to 1 ton of CO2, which can be counted toward meeting the Kyoto targets.
Increasing energy prices over the last few years, as well as enhancements in the process area, make the use of associated gas more and more interesting. Furthermore, the pressure of environmental and political organizations to develop new alternatives to flaring is constantly rising.
Experimental Investigation of Wellhead Twin-Screw Pump for Gas-Well Deliquification
Authors: Morrison Gerald L. , Kroupa Ryan , Patil Abhay , Xu Jun , Scott Stuart , Olsen Sven 
Published: March 2015

Summary
Onshore gas developments are often characterized by drilling, fracturing, and production of wells before low-pressure gas-gathering systems are in place. As well production declines, liquid-loading issues begin to appear. Gas-well deliquefication (GWD) can be accomplished with compression or in-well artificial-lift methods or both. Wellhead wet-gas compression is desirable in that it does not require well intervention to provide GWD, and it is especially useful in maintaining well production in the interim period before field-wide compression is available. Even when fieldwide compression is available, local wellhead compression is desirable at various locations in a field as high-rate wells are added or for wells located at peripheral locations. The use of a twin-screw pump to provide boost for high-gas-volume-fraction (GVF) multiphase flow was investigated experimentally. Tests were conducted with pressure rises ranging up to 250 psi for GVF’s greater than 90%. Water and air were used as the working fluids. The pumping system is a commercially available 230-gal/min twin-screw pump (60 hp) with a design speed of 3,600 rev/min used in conjunction with a knock-out tank that recirculates liquid from the pump exit to provide seal flush. The amount of electrical power required to operate the pump, the inlet liquid- and gas-flow rates, the pressure rise, and the inlet and exit temperatures were recorded. From these data, the volumetric efficiency (flow rate), pump effectiveness, and mechanical efficiency were calculated. Because there is a fixed clearance between the rotating screws and the pump housing, there is a leakage from the high- to low-pressure regions of the pump that will reduce the volumetric efficiency of the pump. It was found that the volumetric efficiency decreased significantly with decreasing pump speed and increasing GVF. At full speed, the volumetric efficiency was between 70 and 88% at ?P=50 psi. Increasing ?P to 250 psi decreased these values to 55 and 81%, respectively. The mechanical efficiency was relatively constant over the pressure-rise range, varying from a high of 48% at the lowest inlet pressure (10 psig) at 0% GVF to a low of 14% for both inlet pressures (10 and 50 psig) at 100% GVF. Overall, the testing demonstrated the ability of a surface twin-screw pump to provide wet-gas compression.
Simulation of Multiphase Fluid-Hammer Effects During Well StartUp and Shut-In
Authors: Han Guoqing , Ling Kegang , Khor Siew Hiang , Zhang He , Thakur Ram K. 
Published: March 2015

Summary
In this study, well-known commercial software that is capable of modelingfully transient multiphase flow in wellbore and pipeline has been used to characterize the fluid-hammer effects of well shut-in and startup on the coupled subsurface and surface systems. The original work was performed byapplying sensitivity analysis to a typical production system, including wellcompletion, wellbore, downhole equipment (e.g., packer), and the associated surface equipment (i.e., flowline, riser, and valves). This study summarizesthe general course of key factors that worsen the fluid-hammer effects. Fluidhammer is also known as water hammer, a shock wave produced by the sudden stoppage of, or reduction in, fluid flow.
Field operations, such as pressure-transient analysis, facility maintenance,and workover, require a well shut-in process. For a typical production system,the resultant sudden rises in pressure can be critical because they have adirect impact on equipment (i.e., unsetting of the packer) and may cause damageto instrumentation. This paper provides estimates of the typical ratio oftransient shock in pressure and flow rate to preconditional values, and theduration of such pressure shocks. It also proposes the best location for theshut-in valve and the length of flowline needed to reduce the fluid-hammereffects.
This is a pioneering approach to integrate multiphase-flow modeling oftransient fluid-hammer effects by targeting flow-assurance issues. The software used in the study is a fully transient, commercial flow-assurance simulator,and it has been used extensively for well-dynamics studies. The selected toolenables the integrated approach [i.e., from sandface (bottomhole) to wellheadand topside platform accordingly], which can be applied to surface-facilitydesign and can serve as guidance in field operation to avoid hydrocarbon leakages.
Novel Leak Detection Method for Sulfur Recovery Unit Condensers
Authors: Cheung Timothy , Scheck Michael , Goodmurphy Adam 
Published: March 2015

Summary
At a Shell sour-gas processing facility in Alberta, Canada, hydrogen sulfide contained within the natural gas is converted into elemental sulfur by means of a sulfur recovery unit (SRU). Tube leaks present in a water-cooled SRU condenser can lead to a variety of process issues, including corrosion and the oxidative formation of acidic species. Leak indicators, such as loss of sulfur flow in the rundown and a frothy sulfur appearance, were observed. This work devised a novel method to verify such leaks within a SRU condenser. Using basic pump equipment and an inexpensive commodity chemical tracer, lithium hydroxide, a leak was diagnosed without the shutdown of the unit and with a minimal of expenditures and hazards to operators. The unit was inspected and the tube leak plugged, which enabled the resumption of normal operations.
New Method To Estimate Surface-Separator Optimum Operating Pressures
Authors: Ling Kegang , Wu Xingru , Guo Boyun , He Jun 
Published: March 2015

Summary
The significance of setting optimal surface separation pressures cannot be overemphasized in surface-separation design for the purpose of maximizing the surface liquid production from the wellstream feed. Usually, classical pressure volume-temperature (PVT) analysis of reservoir fluids provides one or several separator tests through which the optimum separator pressures are estimated. In case separator tests are not available, or the limited numbers of separator tests are not adequate to determine the optimum separator pressures, empirical correlations are applied to estimate the optimum separator pressures. The empirical correlations, however, have several disadvantages that limit their practical applications.
In this study, we approached the problem with a rigorous method with a theoretical basis. According to the gas/liquid equilibrium calculation, the optimum separator pressures were determined. Comparisons of our results with experimental data indicated that the proposed method can simulate the separator tests very well. Because the method has a theoretical basis and does not require existing two-stage or multiple-stage separator-test data as in the application of empirical correlations, it potentially has wide applications in practice for a variety of conditions and yields a more optimal separation scheme than the empirical correlations. Furthermore, the method is independent of reservoir fluid. In the event that separator tests are available from fluid analysis, our method can be used as a quality-control tool. Because the setting for optimal separation pressures vary as the composition of the wellstream changes during the field life, our method provides a quick and low-computational-cost approach to estimate optimum separator pressures corresponding to different compositions.
Pipeline Integrity Assessment Using Probabilistic Transformation Method and Corrosion Growth Modeling Through Gamma Distribution
Authors: Younsi Karim , Chebouba Ammar , Zemmour Nordine , Smati Abdelnacer 
Published: March 2015

Summary
This paper presents a methodology to estimate the probability of failure of every individual corrosion defect and the residual likelihood of failure of an overall corroded pipeline segment after selected repairs, using structural probabilistic analysis based on the assumption of a stationary gamma distribution of the corrosion process. Metal loss size is taken as the load condition, and the allowable depth of the defect is taken as the resistance condition. The load condition is obtained applying the probabilistic transformation method (PTM) and the resistance condition is obtained through Monte Carlo simulation.
Using inspection data collected on a gas pipeline segment pigged two times, results of the suggested methodology are compared with those obtained by a classical approach based on a Gaussian distribution. It is determined that the use of Gaussian model overestimates for a short time horizon after inspection the failure probability, and suggests many useless repairs. The model developed in this paper instead authorizes a more rigorous estimation of failure probability and a significant reduction of maintenance costs.
Use of the ALARP Principle for Evaluating Environmental Risks and Impacts of Produced-Water Discharged to Sea
Authors: Valeur Jens R. , Petersen Johannes 
Published: March 2015

Summary
When produced water from offshore production is discharged to sea, itcontains some oil (aliphatic and aromatic components), production chemicals,and naturally occurring radioactive materials (NORM). These groups of materialsare traditionally treated in different ways in the regulations andstandards.
Regulations of oil in produced water are mainly related to maximumconcentrations and the total discharge of the aliphatic (dispersed) fraction.Regulation of chemicals is based on the environmental risk profile of eachproduction chemical, although efforts are made toward regulations based on riskassessment of the discharge of the mixture of substances. For discharge of NORMdissolved in the produced water, no limit values are imposed. For NORM solids(scale, sludge, sand) from process equipment, discharge to sea is in generalnot allowed--it is reinjected or taken to a deposit onshore.
Management of safety risks takes place on the basis of the principle thatrisks shall be reduced to a level as low as reasonably practicable (ALARP). Theconcept of environmental risk is not as unambiguously defined as safety risks.With respect to accidental environmental impacts, the parallel is relativelystraightforward, but with respect to planned environmental impacts (e.g.,emissions/discharges during operation), the parallel to the safety ALARP levelis not so clear; the consequence (the environmental impact) is not linked to acertain frequency (i.e., we cannot talk about risk as likelihood timesconsequence).
Costs are normally defined as money, effort, and time. But what if the costof a reduced health, safety, and environmental (HSE) risk or impact is anincrease in another HSE risk or impact? Produced-water reinjection might causeincreased carbon dioxide (CO2) emissions. Handling solid NORM duringshipping to shore causes health risks to the people handling the NORM. Can thatrisk be justified on the basis of the possible reduction in environmentalimpact by not discharging the solid NORM to sea instead?
This paper highlights the aforementioned issues and proposes a method called’integrated HSE ALARP assessment’ for supporting such analysis. Theenvironmental risks and impacts of discharge of oil, chemicals, and NORM,respectively, with produced water to sea are used to illustrate theseprinciples.
Simulation of Polymer Injection Under Fracturing Conditions—An Injectivity Pilot in the Matzen Field, Austria
Authors: Zechner Markus , Clemens Torsten , Suri Ajay , Sharma Mukul M. 
Published: March 2015

SummaryPolymer flooding leads to enhanced oil recovery by accelerating oil production and improving sweep efficiency. However, because of the higher viscosity, the injectivity of polymer solutions is of some concern and is important to understand to predict incremental oil recoveries. Achieving high polymer-injection rates is required to increase oil-production rates.In the field test performed in the Matzen field (Austria), polyacrylamide polymers were injected for the past 2 years. Coreflood experiments with these polymers showed a significant increase in apparent viscosity because of the viscoelastic properties of the polymer solutions. Also, severe degradation of the polymer solution at high flow velocities was detected. In addition to coreflood experiments, flow experiments through fractures were performed. In these experiments, shear thinning and limited degradation of the polymer solution were observed and quantified.Detailed polymer-injection simulations were conducted that included complex polymer rheology in the fractures and the matrix. The reservoir stress changes and their effects on the fractures were also taken into account as a result of cold-polymer injection. The results of the simulations matched the field data both for waterfloods and polymer-test floods.The simulations revealed two distinct phases during the injection of the polyacrylamide-polymer solution:Injection under matrix conditions in an early phase resulting in severe degradation of the polymers Injection under fracturing conditions after the formation parting pressure is reached, leading to limited degradation of the polymersThe calibrated model was used to investigate the impact of polymer rheology and particle plugging on injectivity and fracture growth.The results of the field test and the simulations indicate that screening of fields for polyacrylamide-polymer projects needs to include geomechanical properties of the reservoir sand and cap/base rock in addition to the conventional parameters used in screening such as oil viscosity, water salinity, reservoir temperature, and reservoir permeability.
Energy-Efficiency Technologies for Reduction of Offshore CO2 Emissions
Authors: Mazzetti Marit Jagtøyen , Nekså Petter , Walnum Harald Taxt , Hemmingsen Anne Karin T. 
Published: March 2015

Summary
This paper will discuss novel technologies for increasing the energy efficiency of offshore oil and gas platforms. Three case studies are in progress that are based on actual oil-producing platforms--two on the Norwegian Continental Shelf (NCS) and one in the Brazilian basin. The current focus is on developing compact, novel bottoming cycles for recovery of waste heat from the gas turbine and heat recovery from the compressor train for gas export. The technologies under investigation use steam and alternative working fluids, such as carbon dioxide (CO2) and hydrocarbons. All the fluids investigated in this project are natural working fluids; hence, they will not cause any unexpected environmental issues in the future. A case study was performed that considered an 18-year period of operation on an actual platform and a scenario in which one gas turbine was removed and replaced with a CO2 bottoming cycle by use of the exhaust heat from a different gas turbine. The beauty of this scenario is that it would not increase the weight on the platform because the crate containing the gas turbine to be removed was of a weight similar to that of the crate containing the CO2 bottoming cycle. The substitution would not affect the ability to cover the heat demand on the platform because a waste-heat-recovery unit (WHRU) could be installed on the platform's other gas turbine. The case study indicates a significant reduction in CO2 emissions of 22% (63 000 t/a), and does not involve adding additional weight or volume to the platform. If operating on the NCS, the annual savings in reduced fuel costs and CO2 tax from implementing this scenario would be USD 17 million, although much lower in other territories.
The Development of High-Strength Coiled Tubing with Improved Fatigue Performance and H2S Resistance
Authors: Valdez M. , Morales C. , Rolovic R. , Reichert B. 
Published: March 2015

Abstract
In the recent years coiled tubing (CT) has become an integral part of many well completion programs. The trend is to higher-strength CT, larger tube diameters and higher pumping pressures while employing relatively small CT spools to satisfy transportation logistics. Coiled tubing is now routinely used at stress and strain levels that significantly exceed prior experience. These conditions have identified limitations within currently available CT products. Today there is a need for higher-strength CT grades with better resistance to severe environments and better fatigue performance in both the tube body and bias weld.
A detailed study of the metallurgical basis of each production step was performed in order to understand the limitations of the current CT technology and manufacturing process. This understanding, coupled with the goal of developing new CT grades that satisfy new market demands, has resulted in a complete redesign of the CT technology and manufacturing process. Extensive trials have been performed, and a prototype manufacturing facility has been constructed to produce new tubing grades. Comprehensive mechanical testing, metallurgical evaluation, low-cycle fatigue testing, and sour (wet H2S) exposure testing of new 110 ksi and 125 ksi grades produced by the new manufacturing process were conducted. The fatigue testing was performed over a broad range of bending strain and hoop stress that anticipates severe operating conditions. Sour exposure testing included static, sulfide stress cracking (SSC) and hydrogen induced cracking (HIC) testing, as well as dynamic, low-cycle fatigue testing after sour exposure.
Laboratory and field testing of commercial-size strings has shown the fatigue life of the new CT grades exceeds the fatigue life of currently available high-strength grades. Additionally, the bias-weld fatigue life is improved significantly, both in general and relative to the base-tube fatigue life. SSC resistance of the new CT grades is considerably better than the SSC resistance of the conventional CT grades with the same strength, making it possible to increase the tubing material strength by about 20 ksi to 30 ksi without deteriorating the sour resistance.
The paper presents comprehensive information on the new CT grades, their performance in various environments under a wide range of loading conditions, as well as the qualification of the new tubing grades for field use. This allows CT operators and users to select more suitable CT grades for their applications. These new tubing grades also can enable field operations with coiled tubing that cannot be conducted safely and reliably with the currently available tubing grades.