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This article describes a method for measurement of the photodesorption yield and sticking probability for a vacuum chamber coated with nonevaporable getter (NEG). This method is based on a three-gauge method of measurement which was developed and used on a specially designed and assembled setup for the photodesorption yield measurements of test chambers. It has been modified for photodesorption measurements of a vacuum chamber with sorbing walls. Although a short description of the installation and the results of the photodesorption measurements with the NEG-coated vacuum chamber have been published [V. V. Anashin, I. R. Collins, R. V. Dostovalov, N. V. Fedorov, A. A. Krasnov, O. B. Malyshev, and V. L. Ruzinov, The 8th European Particle Accelerator Conference, Paris, France, 2002, p. 2550; Vacuum 75, 155 (2004)], the details of the method, the analysis, and the experimental setup are also described in this article. Special attention is paid to define the sensitivity limit of the method and the setup and to reduce electron- and photon-stimulated desorption in the measurement port.This article describes a method for measurement of the photodesorption yield and sticking probability for a vacuum chamber coated with nonevaporable getter (NEG). This method is based on a three-gauge method of measurement which was developed and used on a specially designed and assembled setup for the photodesorption yield measurements of test chambers. It has been modified for photodesorption measurements of a vacuum chamber with sorbing walls. Although a short description of the installation and the results of the photodesorption measurements with the NEG-coated vacuum chamber have been published [V. V. Anashin, I. R. Collins, R. V. Dostovalov, N. V. Fedorov, A. A. Krasnov, O. B. Malyshev, and V. L. Ruzinov, The 8th European Particle Accelerator Conference, Paris, France, 2002, p. 2550; Vacuum 75, 155 (2004)], the details of the method, the analysis, and the experimental setup are also described in this article. Special attention is paid to define the sensitivity limit of the method and the setup and t...

New types of anodised aluminium, porous copper and charcoal-based materials are being developed as cryosorbing materials and have been studied in collaboration with a number of research institutes. The major aim was to find a suitable cryosorber with a working temperature in the range between 5 and 20 K that could be used in the LHC vacuum chamber inside the superconducting magnets at a temperature of 4.5 K and higher. The design of the experimental set-up, the results of cryosorption capacity measurements for porous copper, anodised aluminium and charcoal-based materials are described in this paper.

A new carbon fibre material was developed at the Institute of Solid State Chemistry and Mechanochemistry at the Siberian Branch of the Russian Academy of Science (SB RAS) to meet the requirements of a cryosorber for the large hadron collider (LHC) vacuum chamber. The material must have a large sorbing capacity, a certain pumping speed, a working temperature range between 5 and 20 K, a low activation temperature (below room temperature), a certain size in order to fit into the limited space available and it should be easy to mount. The vacuum parameters of the LHC vacuum chamber prototype with a carbon fibre cryosorber mounted onto the beam screen were studied in the beam screen temperature range from 14 to 25 K at the Budker Institute of Nuclear Physics SB RAS. This carbon fibre material has shown sufficient sorption capacity for hydrogen at operational temperatures of the beam screen in the LHC long straight sections. It is also very important that this material does not crumble and makes a convenient fixation onto the beam screen in comparison to the widely used granulated charcoal. The problem of fluff and ways of reducing the quantity of fluff in the beam channel were studied. The results of these studies show that the carbon fibre material is a possible cryosorber-candidate for use in the LHC and other long vacuum system at cryogenic temperatures. The experimental set-up and results of measurements of the H 2 cryosorption capacity of this carbon fibre material are presented in this paper.

In the vacuum science community, it is now commonly accepted that, for the present and next generation of accelerators, the surface electronic properties of the vacuum chamber material have to be studied in detail. Moreover, such studies are of valuable help to define the cleaning procedures of the chosen materials and to identify the most efficient vacuum commissioning. In the case of the large hadron collider (LHC) the proton beam stability, in the presence of an electron cloud, is analysed using beam induced electron multipacting (BIEM) simulations requiring a number of surface related properties, such as photon reflectivity, electron and photon induced electron emission, heat load, etc. and their modification during machine commissioning and operation. Such simulation codes base their validity on the completeness and reliability of the aforementioned input data. In this work we describe how a surface science approach has been applied to measure, total electron yield (SEY) as well as energy distribution curves excited by a very low-energy electron beam (0–320 eV), from the industrially prepared Cu co-laminated material, the adopted LHC beam-screen material, held at cryogenic temperatures (about 9 K). The data show that the SEY converges to unity at zero primary electron energy and that the ratio of reflected to secondary electrons increases for decreasing energy below about 70 eV, and becomes dominant below electron energies of about 20 eV. These observations lead to the notion of long-lived low-energy electrons in the accelerator vacuum chamber, which could be an issue for the LHC, damping rings and future accelerators.

A three-gauge method of measurements (Nucl. Instrum. Methods A 359 (1995) 110) is described and used to study the photodesorption yields and sticking probabilities of a stainless steel test chamber coated with approximately 3 μm of TiZrV getter material. Using the measured sticking probability for hydrogen of 0.007 for the TiZrV coated chamber and the known sticking probabilities of CH4, CO and CO2 of 0, 0.5, 0.5, respectively (Vacuum 60 (2001) 57), the photodesorption yields are deduced. After activation, the H2, CH4, CO, and CO2 desorption yields are found to be 1.5×10−5, 2×10−7, These results are compared to those from stainless steel test chamber measurements performed for the same geometry under identical conditions. After saturation with CO and during continuous CO injection, the effect of the irradiation is to reduce the pressure, contrary to the normal dynamic behaviour of a conventional vacuum system. This observation is explained in terms of photon induced pumping of the CO by the TiZrV coating.

The cold bore experiment installed in the super proton synchrotron has been used to study the performance of a vacuum system operating at cryogenic temperatures in the presence of a large hadron collider (LHC) type proton beam. The ∼2 m long cryostat, which can be cooled below 3 K, is fitted with an actively cooled beam screen which can be temperature controlled between 5 and 100 K. Molecular desorption and deposited heat load measurements, with or without gas pre-condensation, have been performed. Implications to the LHC design and operation will be discussed.

The vacuum chamber inside the cryogenic magnets in the LHC Long Straight Sections will have a beam screen at a temperature between 5 and 20 K to protect the cold bore against the synchrotron radiation, electron and ion exposure. The desorbed molecules of H 2 will leave the inner part of the beam screen through the pumping slots on the beam screen and eventually condense on the cryosorber, which is mounted on the shadowed (outer) part of the beam screen for magnets operating at 4.5 K. The design of the experimental set-up, the results of the adsorption capacity measurements for charcoal, the pumping speed and the capture factor of the beam screen with charcoal for a proposed LHC vacuum chamber configuration are described in this paper.

A cryogenic vacuum system has been used to study both the surface pumping of gases and the molecular photodesorption yield from OFE copper in the temperature range from 5 to 300 K. The sticking coefficient on a ‘bare surface’ was found to increase with decreasing temperature of the substrate and below 20 K, to be in the range of a few per cent for all gas species studied. The molecular photodesorption yield for the ‘bare surface’ was found to decrease with decreasing temperature and below 20 K, after an accumulated photon dose of 3.1×10 22 photons m −1 , to be in the range of 10 −4 molecules photon −1 for H 2 and 10 −5 molecules photon −1 for the other gas species. These measured values are used to predict the evolution of the gas densities in the large hadron collider (LHC). Implications to the LHC are discussed.

The design of the large hadron collider (LHC) vacuum system requires a complete understanding of all processes which may affect the residual gas density in the cold bore of the 1.9 K cryomagnets. A wealth of data has been obtained which may be used to predict the residual gas density inside a cold vacuum system exposed to synchrotron radiation. In this study, the effect of cracking of cryosorbed molecules by synchrotron radiation photons has been included. Cracking of the molecular species CO 2 and CH 4 has been observed in recent studies and these findings have been incorporated in a more detailed dynamic gas density model for the LHC. In this paper, we describe the relevant physical processes and the parameters required for a full evaluation. It is shown that the dominant gas species in the LHC vacuum system with its beam screen are H 2 and CO. The important result of this study is that, while the surface coverage of cryosorbed CH 4 and CO 2 molecules is limited due to cracking, the coverage of H 2 and CO molecules may increase steadily during the long-term operation of the machine.

In a cryogenic proton accelerator, such as the LHC, the creation of an electron cloud and generated heat loads resulting from electron bombardment are strongly dependent on the azimuthal distribution of created photoelectrons. In this context, photon reflection and photoelectron yield measurements have been performed using a beam line on the VEPP-2M storage ring. Six electrodes, covering the complete vacuum chamber perimeter, were mounted such that they could be suitably biased, and while one electrode was irradiated with synchrotron radiation the resulting electron current of all the others could be measured. A detailed description of the experimental apparatus and the results of the measurements of photon reflection and the azimuthal distribution of generated photoelectrons are presented.

Summary The deposition of scale, such as carbonates and sulphates, in production facilities represents a serious operational problem that can result in significant well productivity decline. Current scale control strategies can involve significant capital and operational expenditure. Development work, involving laboratory testing and a field trial, has demonstrated the technical benefits of a revolutionary method of downhole scale inhibitor delivery that can prevent scale deposition for a significant proportion of a well's lifetime. The method involves the slow release of scale inhibitor from porous proppants. Economic analysis indicates that significant benefits can be derived for a variety of field development and well completion types. The greatest economic benefits would be realized for subsea and minimum facility installations with high intervention costs, where squeeze delivery of inhibitor or mechanical workover are used for scale control. In addition, major economic benefits can be realized for horizontal wells with unfavorable pressure regimes, multilateral-type completions, multiple fractured wells, and many conventional completion types. The new chemical delivery method offers cost reduction through reduced deferred oil, efficiency of chemical usage, and fewer workovers using coil tubing and intervention vessels. Economic analysis has indicated that for some conventional and advanced well types, fracturing a well and deploying proppant impregnated with scale inhibitor, is economically preferable to a conventional strategy of squeeze treatment in an unfractured well. An additional economic benefit of proppant impregnated with scale inhibitor is increased well productivity. The benefit is derived from the combined effect of improved gel breaking, and scale inhibition during well cleanup. This has been demonstrated in laboratory testing and would appear to be confirmed by field observations. A further benefit of applying scale inhibitor as chemically impregnated proppant is the immediate treatment of produced water when water breakthrough occurs. This feature avoids the formation damage that can occur before squeeze treatment mobilization. In addition, for some applications involving large fractures there is the potential for lifetime well treatment. This paper describes the laboratory work, the field trial, and the economic benefits of the new product.

For the design of future accelerators, in particular, the beam vacuum of the large hadron collider (LHC), a 27 km circumference proton collider to be built at CERN, ‘white light’ (WL) and monochromatic VUV synchrotron radiation (SR) have been used to measure, both qualitatively and quantitatively, electron emission from candidate vacuum chamber materials. Emphasis has been placed on measuring the photoelectron yields (PY) and the energy distribution of the emitted electrons. These parameters are relevant to gas desorption, the LHC cryogenic cooling capacities and the possible creation of an electron cloud which may cause beam instabilities. Proposed materials, prepared on an industrial scale, such as 50 μm OFE Cu co-laminated onto a high Mn-content stainless steel, exhibit significant modifications when exposed to the WL spectrum from the BESSY TGM7 beamline. Surface cleaning treatments, such as sample annealing and ion bombardment, induce substantial changes to the electron emission which therefore indicate that such surfaces would not be constant, in terms of electron emission, during machine operation. Surfaces which are considered to be constant electron emitters, such as annealed TiZr alloys and commercial non-evaporable getters, were also investigated. These results and their implications for the choice of the material to be used for the LHC are discussed.

Summary Barium sulfate scale deposition in the near wellbore, perforations, or production tubing has severely affected well productivity in many North Sea Fields. This is due to the co-mingling of the sulfate-rich seawater used for reservoir sweep with formation water containing high concentrations of barium ions. Mitigation of this problem is generally achieved by regular "squeeze" deployment of scale inhibitor chemicals which retard scale precipitate formation and deposition. However, in some instances, the scale inhibitor is poorly retained within the reservoir rock matrix and short squeeze lifetimes are experienced. The net result in these cases is frequent well interventions which impact on both well productivity and field profitability. To solve this problem, a scale squeeze enhancer has been developed which acts to enhance retention and subsequent release of scale inhibitor in the reservoir. The first field deployment of this technology was in BP's Magnus asset. The trial demonstrated a more than doubling of the squeeze lifetime of an adsorption chemical.

A detailed theoretical study of the filled outer-shell core levels of Ta(110) by bandstructure and photocurrent calculations of core level photoemission experiments is presented. The important question of the existence of bulk bandstructure effects in these levels is addressed. Bandwidths of 47 meV and over 1 eV are both shown to exist within the 4 f 7 2 and 5 p 3 2 levels, respectively, and to be important in the interpretation of the core level photoemission spectra. The implications of these effects within the core levels of Ta(110) are discussed.

Angle-resolved photoemission spectroscopy (ARPES), using HeI radiation, has been used to probe the occupied electronic states from a single domain of the Au-induced 5 × 2 reconstruction of Si(111), a quasi-one-dimensional (quasi-1D) metallic system. The ARPES spectra recorded parallel (perpendicular) to the Au chain structure show a signature of a metallic (non-metallic) system. These experimental results are intriguing since, for the first time, spectral intensity at the Fermi level is observed in a photoemission study of a quasi-1D metallic system.

The properties of the electrons participating in the build up of an electron cloud (EC) inside the beam-pipe have become an increasingly important issue for present and future accelerators whose performance may be limited by this effect. The EC formation and evolution are determined by the wall-surface properties of the accelerator vacuum chamber. Thus, the accurate modeling of these surface properties is an indispensible input to simulation codes aimed at the correct prediction of build-up thresholds, electron-induced instability or EC heat load. In this letter, we present the results of surface measurements performed on a prototype of the beam screen adopted for the Large Hadron Collider (LHC), which presently is under construction at CERN. We have measured the total secondary electron yield (SEY) as well as the related energy distribution curves (EDC) of the secondary electrons as a function of incident electron energy. Attention has been paid, for the first time in this context, to the probability at which low-energy electrons (< 20 eV) impacting on the wall create secondaries or are elastically reflected. It is shown that the ratio of reflected to true-secondary electrons increases for decreasing energy and that the SEY approaches unity in the limit of zero primary electron energy. PACS numbers: 79.20.Hx ; 29.27.Bd; 41.75.Lx

Gas well Groet 1 (GRT1), located onshore in the Netherlands, has been experiencing unstable production for six months since Q1 2002. A down hole video survey identified salt (halite) deposition in the tubing which was subsequently removed by a gauge cutter. The problem reoccurred in Q4 2002 leading to an 8.3 MBOE loss in the quarter. A scale prediction study was conducted to analyse the problem arising with well GRT1 and to diagnose whether the scaling problem is transient or persistent. This study indicated that the scaling behaviour is persistent. Several remedial actions and control options were considered, based upon the diagnosis. All of the remedial actions and control options were compared on a risk / cost / benefit basis. The outcome of this study was that the most economical and lowest risk halite control option was bi-weekly fresh water soaks.

The risks and uncertainties associated with scale control in new field developments can often have a significant impact on the field economics. This can be especially true for marginal subsea fields producing from areas with high barium concentrations in their formation waters. Other aspects such as completion design, reservoir formation and heterogeneity also have a significant impact both on the severity of the scaling potential and also the ability to effectively treat production wells via conventional bullhead squeeze treatments. In this paper we describe an analysis that was conducted during the Pre-Front End Engineering and Design (FEED) stage of a field in the Norwegian sector of the North Sea. The field was expected to produce hydrocarbons from two subsea templates located 1.6km and 6.3km from a floating production system over a field life of ~ 10 years. Seawater injection was preferred over gas injection for pressure support owing to the higher predicted hydrocarbon recoveries. Of particular concern was the high barium concentration of > 700 ppm recorded from an appraisal well water sample, indicating a very severe barium sulphate scaling potential with raw sea water injection. For this field, in addition to the very severe potential barium sulphate scaling regime, a number of factors combined to present an exceptionally severe risk to the fields net present value. This related to: subsea completions with multiple production wells co-mingling at the wellheads (although dual production lines were incorporated into the design plan partially to assist in scale management); and long (500 - 700m) horizontal production wells and completion designs involving open hole screens served to increase the risks associated with scale formation and effective chemical placement. A range of alternative options were examined together with the associated risks and uncertainties. In summary, the most significant risks and uncertainties associated with the economic viability for seawater injection in this field related to: Uncertainties associated with the initial formation water composition.The ability to squeeze treat wells without inducing fines mobilization and plugging sand control screens as observed in analogue fields.The ability to effectively place scale inhibitor treatments along the length of the horizontal producers by bullhead treatments rather than coil tubing operations.The potential for changes in the base case field production scenario This work therefore allowed the design team to make informed decisions at the pre-FEED stage in a field where scale control had a significant impact on the fields economic viability.

Oilfield scale formation is dependent upon the production of water and as a result most scale inhibitors are water soluble and deployed using an aqueous phase. For treatment of wells that produce only small amounts of water and/or have water sensitive matrices and wells with high water cuts with lifting problems the use of an aqueous inhibitor can cause many problems. Even with the development of oil miscible and emulsified scale inhibitors the same problem can be encountered when the incorrect screening procedure has been used in the laboratory. This study describes the development of a range of truly oil soluble scale inhibitors for squeeze application. A particular feature of these materials is that they preclude aqueous phases and are soluble in crude oil and diesels. The products have been designed so that is possible to deploy calcium sensitive scale inhibitors in a non-aqueous medium. Upon contact with formation water passing the near wellbore the scale inhibitor will partition into the water phase and undergo a precipitation reaction. This provides a mechanism for potentially increasing treatment lifetime. In addition, the scale inhibitor precipitation can be further controlled and enhanced through emulsification with a calcium loaded aqueous medium also containing organic additives to aid and enhance the precipitation process. Although this involves incorporating water into the product package the invert emulsion provides an oil continuous matrix and is still considered to be significantly less damaging to water sensitive formations than standard oil dispersible and emulsified scale inhibitor packages. A detailed investigation into the properties of selected oil soluble and emulsified products has been performed. Experimental data on compatibility with production fluids, thermal ageing, oil/water partitioning, inhibitor performance, extent of precipitation and core flood studies to evaluate formation damage potential and retention and release characteristics will be presented. This paper will also highlight how the use of the oil soluble precipitation process can increase squeeze lifetimes when compared to traditional aqueous squeeze treatments. In addition, a new core flood procedure for the screening and evaluation of non-aqueous chemical treatments will be described and the implications this has for field application of these products will be discussed.

‘Oil Soluble’ scale inhibitor delivery systems are believed to have been first applied to an onshore well in Colombia in 1997. Products of a similar type have since been used in a number of applications including wells in the UK and Norwegian Sectors of the North Sea and in North America. In addition to oil soluble products, other technologies designed to avoid the problems sometimes observed with aqueous treatments have also been developed and deployed in similar, challenging, environments. The different technologies are now commonly referred to as non-aqueous systems to distinguish them from more traditional, aqueous methods. This paper will review each of the non-aqueous technologies currently available followed by a detailed description of field experiences, both good and bad, found by BP, ChevronTexaco, Statoil and other operators using oil soluble systems. Where problems were encountered, the laboratory work to investigate these difficulties will be described and the main findings presented. Recent advances using the knowledge gained from the investigation of earlier challenges will also be presented.

The control of inorganic scale deposition within the reservoir under both natural depletion and injection water support has been a challenge to the oil industry for a number of decades. The challenge has remained identifying the location of water breakthrough within the production interval and the subsequent injection of scale inhibitor into these zones to prevent scale formation within the near welbore and production tubing. As completion technology has advanced, and more complicated completions have been developed and installed to increase the rate of oil recovery, the challenges of water management and scale control have become significant factors if long term production from these wells is to be maintained.This paper will outline the challenges of chemical deployment via bullheading into subsea wells completed in high permeability reservoirs with sand control technology. The factors considered when designing a self-diverting scale inhibitor system will be outlined in terms of viscosity profile of the chemical and overflush fluid, impact of temperature on fluid viscosity, pump rate, shear effects, tubing diameter vs. wellbore friction and the impact of radial flow on viscosity. Modelling data from vertical and horizontal production wells will be used to illustrate the challenges that pump rate changes and a self-diverting scale inhibitor system has to overcome to allow effective deployed of scale inhibitor without the need for coiled tubing in long (500ft to 3,000 ft) wells in 2 Darcy reservoirs.The value of this technology in terms of the economic factors will be outlined with field examples where coiled tubing and bullhead applications will be compared and contrasted to illustrate the value in terms of total cost of operation that the self-diverting technology can offer.

In particle accelerators with intense positively charged bunched beams, an electron cloud may induce beam instabilities and the related beam induced electron multipacting (BIEM) can result in an undesired pressure rise. In a cryogenic machine such as the large hadron collider (LHC), the BIEM will introduce additional heat load. When present, synchrotron radiation (SR) may generate a significant number of photoelectrons, that may play a role in determining the onset and the detailed properties of the electron cloud related instability. Since electrons are constrained to move along field lines, those created on the accelerator equator in a strong vertical (dipole) field cannot participate in the e-cloud build-up. Therefore, for the LHC there has been a continuous effort to find solutions to absorb the photons on the equator. The solution adopted for the LHC dipole beam screens is a saw-tooth structure on the illuminated equator. SR from a bending magnet beamline at ELETTRA, Italy (BEAR) has been used to measure the reflectivities (forward, back-scattered and diffuse), for a flat and a saw-tooth structured Cu co-laminated surface using both white light SR, similar to the one emitted by LHC, and monochromatic light. Our data show that the saw-tooth structure does reduce the total reflectivity and modifies the photon energy distribution of the reflected photons. The implications of these results on the LHC arc vacuum system are discussed. © 2004 Elsevier B.V. All rights reserved.

Water in oil (w/o) formulations containing a range of scale inhibitors have been prepared for squeeze application. Depending on their composition these have been found to be either microemulsions or weakly structured mixtures.A particular feature of the materials described is the type and concentration of surfactant used. High concentrations of surfactants are traditionally required to generate and stabilise conventional microemulsions. However, the back-production of the surfactants following a squeeze may cause undesirable process upsets. To minimise these upsets and to maximise the performance of the delivery technique, novel complexing agents, which, when combined with suitable scale inhibitors, form semi-stable species capable of stabilising w/o systems have been developed.A detailed investigation of the properties of selected materials has been performed and experimental measurements including phase behaviour, reservoir condition coreflood tests and inhibitor desorption data are presented. A new technique which provides data in-line with core performance tests is also described.The possibility to utilise the phase behaviour of these materials to increase squeeze life is also explored. Data for Miller Field conditions, showing an increase in squeeze life, are presented.

The vacuum stability is studied for the LHC experimental beam vacuum chambers of ALICE, ATLAS, and CMS. The present baseline design includes sputtered non-evaporable getter (NEG) coating over the whole chamber inner surface providing distributed pumping and an antimultipactor coating. The data are presented for the dominant gas species (H/sub 2/, CH/sub 4/, CO and CO/sub 2/) in a baked system. It results that the distributed pumping is necessary for vacuum stability of CO. Lumped pumping with sputter ion pumps (SIP) is also indispensable for the stability of CH/sub 4/. The operational constraints with NEG technology are described.

Mineral scale formation and deposition on downhole and surface equipment is a major source of cost and reduced production to the oil industry. One potential means of preventing losses due to scale is to prevent it adhering/depositing on key components in the production system (such as downhole safety valves and key parts of intelligent well systems). In general, the coatings proposed to prevent deposition of scales are made of low-surface energy materials. However, industry experience of non-adherent coatings is not good and a search of the literature suggests that there are a number of contrary reports on the effects of surface energy on solid deposition behavior. Some reports show that deposits attached preferentially to high surface energy surfaces, while others purport to show that deposits attach preferentially to surfaces with low surface energy. Numerous studies also indicate that there is little relationship between surface energy/wettability and deposition behavior. Obviously a sound theoretical explanation of the observed deposition behaviour on various surfaces is crucial for the development, and deployment, of low-deposition surfaces. In this paper, the extended DLVO theory is used to explain scale deposition behaviour on metal substrates, and on modified metal surfaces. The proposed theory is shown to agree well with the limited experimental data available and thus provides the basis for a sound theoretical approach to controlling and preventing scale adhesion on surfaces

As the industry moves towards increasing deepwater production, the very high cost of well intervention places large constraints upon the performance of scale control options. In particular, where scale is managed by squeeze treating, it is an absolute requirement that the treatment lasts as long as possible and efficiently utilizes the applied chemical. This paper discusses using enhanced oil recovery-type surfactant systems in conjunction with scale inhibitors to dramatically extend the squeeze treatment lifetime. It is believed that the treatment lifetime is extended by the miscible displacement of organic material from formation surfaces thereby increasing the surface area available for the scale inhibitor to adsorb onto. The efficacy of this approach, using simple to formulate packages, is demonstrated by coreflood data in which the lifetime of the treatment is extended by up to four times.

In this paper we describe the development of a novel water-in-oil emulsion system for the deployment of aqueous-based production chemicals. The non-aqueous nature of the emulsion system potentially allows ingress of the chemical into parts of the reservoir normally denied access to an aqueous-based formulation and so can improve contact between the chemical and the reservoir fluids on production. Furthermore, the whole treatment can be deployed as a non-aqueous package allowing oil continuity to be maintained during the treatment. This can (i) prevent changes in the near well-bore relative permeability arising from the influence of the injected fluids; (ii) prevent water becoming trapped in oil-bearing zones reducing permeability to oil; and (iii) improve production chemical penetration depths (the water-wet nature of sandstone reservoirs means that the penetration depth of, for example, scale inhibitor solutions can be low). Moreover, for poor pressure support reservoirs, the reduced density of a non-aqueous treatment can obviate the need for artificial lift to restart the well. Originally developed for scale inhibitor deployment, this technology has been advanced by developing slowly degrading emulsion systems, which provide a means of trapping the aqueous production chemical within the porous media and allowing subsequent controlled release of the chemical. This advanced scale control technology has been proven in the laboratory for the encapsulation of corrosion inhibitors, biocides, hydrogen sulphide scavengers, and chemicals for the control of reservoir souring. Encapsulated scale inhibitors have been field deployed in two locations (in the UK sector of the North Sea and in the demanding environment of onshore Alaska under both high water cut and very low water cut conditions). This paper describes laboratory testing, including coretests, and describes the planning, the execution, and the results of the field treatments.

Production chemicals being discharged into the natural environment are increasingly becoming scrutinized for their impact on the environment. New and existing chemicals for scale and corrosion control are likely to be impacted by the developing legislation and regulatory control. Therefore, there exists an urgent need to bring the marketplace new chemistry that is able to reduce the environmental impact while still retaining its excellent efficiency. This paper describes the development of novel polymeric chemistry, which has a dual functionality acting as both a scale and corrosion inhibitor under oil field conditions. This chemistry can be readily biodegradable and has achieved the stringent standards required for its use in the North Sea. Laboratory studies demonstrate that this chemistry can inhibit both carbonate and sulfate based scales. Corrosion experiments with or without flow suggest that greater than 90% of inhibition in a carbon dioxide rich environment can be achieved. The calcium compatibility of this chemistry far exceeds the performance of most commercially available scale inhibitors. The impact on oil and water separation, and subsequent oil in water content, is minimal.

A novel approach to measure mineral scale growth has been developed which is not only quantitative but also surface sensitive. In this study, a glass flow cell was used in conjunction with Laser Raman Spectroscopy to record the in-situ growth of mixed barium and strontium sulphate scale on the surface of 316 stainless steel. Studies of both uninhibited and inhibited growth are reported as well as the influence of specific ions. All experiments have been performed at room temperature and pressure and at constant solution pH. In order to quantify these measurements, Secondary Ion Mass Spectrometry (SIMS) has been used to etch the precipitated scale from the surface of the steel. As the scale is removed, an elemental analysis of the sputtered ions is performed, resulting in a depth profile, which is sensitive to the presence of scale mineral ions on the steel surface. The etches were then imaged using Scanning Electron Microscopy (SEM). Our data suggests that there was a large surface influence upon inhibition efficiency when compared with previously presented results (e.g. Yuan, 2000). A much higher concentration of inhibitor was required to prevent scale build up, compared with values determined in bulk precipitation tests, indicating the formation of inhibitorsurface complexes. Most previous studies are non-surface sensitive and have utilised aqueous precipitation experiments to evaluate scale inhibition efficiency (Graham et al., 1997). Previous surface sensitive methods have used Atomic Force Microscopy (AFM) to observe scale precipitation and to measure the effect that nhibitors have upon the nature of crystal growth; however, this technique is not rate sensitive and thus the kinetics of scale build up have not been previously obtained (Bosbach et al., 1998).

Precipitation of mineral scales causes many problems in oil and gas production operations: formation damage, production losses, increased workovers in both producers and injectors, poor injection water quality, and equipment failures due to under-deposit corrosion. The most common mineral scales are sulfate and carbonate-based minerals. However, scale problems are not limited to these minerals and there have recently been reports of unusual scale types such as zinc and lead sulfide. This paper focuses on zinc sulfide scale that has been has been found in several fields along the Gulf Coast of the USA and fields within the North Sea Basin. Scale deposition has caused significant pressure and rates reductions in high temperature, high rate gas, condensate and black oil wells. After acid washes to remove zinc sulfide scale (and other acid soluble solids), production rates and flowing tubing pressures returned to previous levels, but new scale deposits formed in many wells and re-treatments were required. Topside process equipment most noticeable low-pressure separators and hydrocyclone were observed to suffer reductions in performance owing to zinc sulfide scale deposition. In addition, there are significant risks associated with acid treatments in high temperature, high-pressure gas wells: corrosivity of the acid at high temperatures (general corrosion, sulfide stress cracking, and chloride stress cracking) and safety (hydrogen sulfide generation by acid dissolution of zinc sulfide plus high pressure pumping). One possible method for preventing production declines and reducing the need for high temperature, high-pressure acid jobs, is to use scale inhibitors or a chelating agents to prevent the formation of zinc sulfide scale. The relative effectiveness of eight scale inhibitor chemistries and two chelating agents in preventing formation of zinc sulfide scale has been determined. The required scale inhibitor concentrations are significantly higher than concentrations needed for common sulfate and carbonate scales. For chelating agents, it is possible to prevent the formation of zinc sulfide scale with the required concentrations being proportional to the Zn2+ ion concentration in the scaling brine. This paper outlines the testing methods utilized for chemical screening and for prediction so that assessment of the potential problem within fields during appraisal can be assessed prior to production commencing and a method of managing the risk made available.

This paper describes the experimental studies of the effect of a dipole field on photoelectron emission and on the photon reflectivities from LHC beam screen material. These studies were performed using synchrotron radiation from the VEPP-2M storage ring at BINP (Novosibirsk). The particular surface roughness and geometry of the prototype LHC beam screen material requires dedicated experimental measurements. The experiments were performed under conditions close to those expected in the LHC. An important result obtained is that a dipole magnetic field attenuates the photoelectron emission from the surface by more than two orders of magnitude with the magnetic field aligned parallel to the surface. The measurements of photon reflectivities, forward scattered and diffuse, and the azimuthal distribution of emitted photoelectrons from the same material are reported. These experimental results are important input for the final design of the LHC beam screen.

Water-in-oil emulsions have been developed which have been shown to be a credible means of deploying scale inhibitors in a non-aqueous medium. Furthermore, the use of slowly degrading emulsion systems provides a means of trapping scale inhibitor within porous media and allowing subsequent controlled release of the chemical. This has been demonstrated using sandpack and coreflood experiments where the lifetime of the inhibitor, as measured by pore volumes of brine eluted to a given inhibitor concentration, has been extended by up to (and possibly beyond) four times compared with the base case non-emulsified product. No permeability damage has been observed for the emulsion systems. The use of emulsion droplets to provide chemical reservoirs within the formation also considerably reduces the wastage of non-retained chemical observed with conventional squeeze treatments. The non-aqueous nature of the emulsion system potentially allows ingress of the scale inhibitor into parts of the reservoir normally denied access to an aqueous-based formulation and so can improve contact between the scale inhibitor and the reservoir fluids on production. Furthermore, the whole treatment can be non-aqueous allowing oil continuity to be maintained during the treatment affording rapid well clean up post treatment.

Chemical inhibitors that prevent the formation of sulphate and carbonate mineral scale formation are used in field squeeze treatments. The demand for competent evaluation of all issues associated with mineral scaling in wells and pipelines is continuous throughout the lifetime of any producing asset and the cost implications are very large. It is therefore important that the chemical inhibitor species can be accurately assayed so that the end of the squeeze lifetime can be determined. Previous work by others has reported the development of accurate detection and assay techniques for oilfield scale inhibitors1,2. For PVS and VS-Co type inhibitors, these methods involve pre-treatment/purification stages that allow the application of standard wet chemical techniques, in particular the separation of the inhibitor chemical from interfering brine salts. However the typical size of samples from experimental core floods are so small that they render these methods impractical. In this paper we detail the development of a turbidimetric method without the need for pre-treatment/purification stages for the determination of a sulphonated-polyacrylate co-polymer using Hyamine 1622. The applicability of this technique is illustrated with coreflood samples having small volume size and with real field post-scale inhibitor squeeze produced water samples. It is also shown that the method developed allows the determination of scale inhibitors in produced waters with up to 55,000ppm total chloride concentration and 100ppm crude oil in water. Finally we report the potential interferences caused by the inhibitor carrier, crude oil and displacement fluid which may arise as a result of both typical and atypical squeeze treatments.

Mineral scaling in the near-wellbore region of oil wells can cause significant formation damage and have a major impact on well productivity. Removal of scale from the reservoir is usually limited to chemical means, or, if the completion is a cased hole, to re-perforating through the damage. Chemical removal of scale from the reservoir is limited by the contact that can be achieved between the scale deposits and the scale dissolver chemical, and by the volume of chemical which can be injected. In addition, scale deposits can become coated in hydrocarbons, preventing contact between the deposit and the chemical dissolver. Furthermore, owing to the nature of the dissolvers (comprised of chelants and acids), there is the potential for the dissolver to cause formation damage by (i) dissolving cementing minerals thereby generating fines; (ii) swelling authigenic clays; and (iii) forming water blocks. We have developed a proprietary mixture of non-ionic materials which has been shown to enhance the dissolution of both calcium carbonate and barium sulfate scales in porous media (using commercial scale dissolvers in the tests). This chemical, when used as a pre-flush, removes hydrocarbon deposits on the scale surface thus increasing the surface area accessible to the dissolver. In addition, the pre-flush chemical might remediate some aspects of dissolver induced formation damage. In this paper we describe laboratory experiments validating the chemical package.

An adequate dose of photoelectrons, accelerated by low-intensity proton bunches and hitting the LHC beam screen wall, will substantially reduce secondary emission and avoid the fast build-up of an electron cloud for the nominal LHC beam. The conditioning period of the liner surface can be considerably shortened thanks to secondary electrons, provided heat load and beam stability can be kept under control; for example this may be possible using a special proton beam, including satellite bunches with an intensity of 15-20% of the nominal bunch intensity and a spacing of one or two RF wavelengths. Based on recent measurements of secondary electron emission, on multi-pacting tests and simulation results, we discuss possible 'beam scrubbing' scenarios in the LHC and present an update of electron cloud effects.

Abstract The deposition of scale, such as carbonates and sulphates, in production facilities represents a serious operational problem that can result in significant well productivity decline. Currently implemented scale control strategies can involve significant capital and operational expenditure. Development work, involving laboratory testing and a field trial, has demonstrated the technical benefits of a revolutionary method of downhole scale inhibitor delivery. Economic analysis indicates that significant benefits can be derived for a variety of field development and well completion types. The greatest economic benefits would be realized for subsea and minimum facility installations with high intervention costs, where squeeze delivery of scale inhibitor or mechanical workover are used for scale control. In addition, major economic benefits can be realized for horizontal wells with unfavourable pressure regimes, multi- lateral type completions, multiple fractured wells, and many conventional completion types. The new chemical delivery method offers cost reduction through reduced deferred oil, efficiency of chemical usage, and elimination of coil tubing and intervention vessel use. Economic analysis has indicated that fracturing a well and deploying proppant impregnated with scale inhibitor, is economically preferable to a strategy of squeeze treatment for some conventionally unfractured wells with high intervention costs, for example subsea wells. An additional economic benefit of proppant impregnated with scale inhibitor (Chemflow) is increased well productivity. The benefit is derived from the combined effect of improved gel breaking, and scale inhibition during well clean-up. This has been demonstrated in laboratory testing and would appear to be confirmed by field observations. A further benefit of applying scale inhibitor as chemically impregnated proppant is the instantaneous treatment of produced water when water breakthrough occurs. This feature avoids the formation damage that can occur before squeeze treatment mobilization. In addition, for some applications involving large fractures there is the potential for lifetime well treatment. P. 323

Abstract Barium Sulfate scale deposition in the near-well-bore, perforations or production tubing has severely affected well productivity in many North Sea Fields. This is due to the commingling of the sulfate-rich seawater used for reservoir sweep with formation water containing high concentrations of barium ions. Mitigation of this problem is generally achieved by regular 'squeeze' deployment of scale inhibitor chemicals which retard scale precipitate formation and deposition. In the squeeze procedure, scale inhibitor is injected several feet radially into the production well where it is retained by adsorption and/or formation of a sparingly soluble precipitate. The inhibitor slowly leaches into the produced water over a period of time and protects the well from scale deposition. However, in some instances, the scale inhibitor is poorly retained within the reservoir rock matrix and short squeeze lifetimes are experienced. The net result in these cases is frequent well interventions which impact on both well productivity and field profitability. To solve this problem, a scale squeeze enhancer has been developed (jointly by BP Exploration and BP Chemicals) which acts to enhance retention and subsequent release of scale inhibitor in the reservoir. The first field deployment of this technology was in BP's Magnus asset. The trial demonstrated a more than doubling of the squeeze lifetime of an adsorption chemical and has subsequently led to considerable cost savings for the Magnus asset by reducing well intervention frequency and subsequent well downtime. Introduction Magnus Field History. The Magnus oilfield lies approximately 160 km north east of the Shetland Islands in the UK Sector of the North Sea. The field is located in blocks 211/7a and 211/12a, and is producing through the most northerly platform on the UKCS. The Magnus oilfield was discovered by BP in 1974 and first production commenced in August 1983, reaching a peak annual average production rate of 144,301 stb/day in 1994. Reservoir Description. The Magnus field is divided into three producing intervals, the Turonian Reworked Sandstone, which overlays the Magnus Sandstone Member (MSM), which overlays the Lower Kimmeridge Clay Formation. The producing interval initially contained an estimated volume of 1,650 mmstb of oil in place. The MSM lies at a sub-sea depth of approximately 3000m and is currently the main producing formation, having originally held 77% of the initial oil in place. The MSM is the most well defined of the Magnus formations, and can be broken down into several discrete sandstone zones or lobes, separated by shale mudstone units, which act as vertical permeability barriers. The typical MSM permeability is in the range 200–500 mD, with an average porosity of 21% and a maximum net pay of 108 m. Reservoir Management. The Magnus reservoir is currently being drained by 15 producing wells, while 9 further wells, including 3 sub-sea tie-ins, are injecting seawater to support the reservoir pressure. However, off-take from the field to date has exceeded the volume injected, resulting in a significant drop in reservoir pressure from an original value of 6650 psi to a current average of approximately 3000 psi. In addition, a significant pressure gradient exists across the field, with a maximum of 7500 psi observed in certain injectors, compared with 2750 psi measured in several crestal producers. The field is now produced on a voidage replacement basis, however, significant differential pressure exists between lobes as a result of divergent pressure depletion through the MSM. Nature of Scale Problem. An analysis of the ionic composition of the formation waters produced from the various lobes or zones reveals subtle differences in their chemistry; however, in each case the produced water has a salinity almost identical to sea water. In addition, the barium concentration in Magnus formation water is in the range 160–220 mg/l. P. 161^

Economic and Technical Advantages of Revolutionary New Chemical Delivery System for Fractured and Gravel Packed Wells P.J.C. Webb, AEA Technology plc, T.A. Nistad, Saga Petroleum ASA, B. Knapstad, Norsk Hydro ASA, and P.D. Ravenscroft and I.R. Collins, BP Exploration Operating Company Limited Copyright 1997, Society of Petroleum Engineers, Inc. Abstract The deposition of scale, such as carbonates and sulphates, in production facilities represents a serious operational problem that can result in significant well productivity decline. Current scale control strategies can involve significant capital and operational expenditure. Development work, involving laboratory testing and a field trial, has demonstrated the technical benefits of a revolutionary method of downhole scale inhibitor delivery that can prevent scale deposition for a significant proportion of a wells lifetime. The method involves the slow release of scale inhibitor from porous proppants. Economic analysis indicates that significant benefits can be derived for a variety of field development and well completion types. The greatest economic benefits would be realised for subsea and minimum facility installations with high intervention costs, where squeeze delivery of inhibitor or mechanical workover are used for scale control. In addition, major economic benefits can be realised for horizontal wells with unfavourable pressure regimes, multi-lateral type completions, multiply fractured wells, and many conventional completion types. The new chemical delivery method offers cost reduction through reduced deferred oil, efficiency of chemical usage, and reduction workovers using coil tubing and intervention vessels. Economic analysis has indicated that for some conventional and advanced well types, fracturing a well and deploying proppant impregnated with scale inhibitor, is economically preferable to a conventional strategy of squeeze treatment in a unfractured well. An additional economic benefit of proppant impregnated with scale inhibitor is increased well productivity. The benefit is derived from the combined effect of improved gel breaking, and scale inhibition during well clean-up. This has been demonstrated in laboratory testing and would appear to be confirmed by field observations. A further benefit of applying scale inhibitor as chemically impregnated proppant is the immediate treatment of produced water when water breakthrough occurs. This feature avoids the formation damage that can occur before squeeze treatment mobilisation. In addition, for some applications involving large fractures there is the potential for lifetime well treatment. This paper describes the laboratory work, the field trial and the economic benefits of the new product. Introduction Production of hydrocarbons is often associated with the deposition of mineral scales from co-produced water. Mixing of incompatible waters, and changes of temperature and pressure can cause deposition of carbonate (CaCO3) and sulphate (Ba/SrSO4) scales in the near wellbore and tubing of production wells. Scale deposition is a recurring operational problem for many conventional and advanced wells worldwide. Preventative and remedial scale control operations often involve significant cost to an operator through equipment and personnel, and deferred oil costs. This paper presents details of the technical and economic features of a revolutionary method of scale inhibitor delivery developed by AEA Technology with the support of Saga Petroleum ASA, Norsk Hydro ASA, and BP Exploration Operating Company Ltd. The delivery concept has many advantages when compared to conventional scale management strategies, as applied to advanced and conventional well completions. The current status of the technology allows simple application in fractured and gravel packed field developments. The considerable potential for applying other types of oilfield chemical is briefly discussed. P. 523^

Abstract Laboratory tests and a field trial have demonstrated the technical and economic benefits of a revolutionary downhole chemical scale inhibitor delivery method. The method also has the potential to be used for other oilfield chemicals, for example corrosion inhibitors and gel breakers. The method involves the controlled release of chemical from impregnated porous ceramic beads, manufactured with the necessary mechanical strength and size properties for direct substitution of proppant, gravel pack sand and prepacked screen beads. This novel concept offers an economically attractive method of chemical delivery for both advanced wells and conventional wells when compared to conventional intervention based delivery techniques, such as squeeze treatments. The concept addresses many of the operational problems associated with chemical treatment of wells completed with multiple fractures, long horizontal sections with unfavourable pressure regimes, remote wells with high intervention costs, and multi-lateral type completions. In general, the concept offers reduced deferred oil costs through reduced well intervention and preservation of pack conductivity, and more efficient chemical use compared to squeeze technology. Wells with fractures containing in excess of 100,000 lb of proppant have the potential for scale inhibitor treatments lasting a significant proportion of a wells lifetime. Prepacked screens containing 3,000 lb of chemically impregnated bead could provide treatment periods of 2 to 36 months. Introduction The deposition of mineral scales, such as carbonates and sulphates, in oil producing wells is a recurring operational problem for conventional and advanced wells. Significant operational costs are incurred when applying preventative or remedial scale control strategies, for example chemical scale inhibitor squeeze treatments or re-perforation, respectively. This paper presents technical and economic details of a revolutionary method of scale inhibitor delivery developed by AEA Technology with the support of Saga Petroleum ASA, Norsk Hydro ASA, and BP Exploration Operating Company Ltd. The delivery concept has many advantages when compared to conventional scale control strategies, as applied to advanced and conventional well completions. The potential for applying other chemical types is briefly discussed. The method of delivery is applicable to production wells completed with propped fractures, gravel packs, prepacked screens, and other intermediate types where beads or proppant are placed in a well.

Note: Univ liverpool,interdisciplinary res ctr surface sci,liverpool l69 3bx,merseyside,england. univ dublin trinity coll,dept pure & appl phys,dublin 2,ireland. ecole polytech fed lausanne,inst phys appl,ch-1015 lausanne,switzerland. univ liverpool,dept phys,liverpool l69 3bx,merseyside,england.ISI Document Delivery No.: RQ630 Reference LSE-ARTICLE-1995-006doi:10.1016/0039-6028(95)00438-6View record in Web of Science Record created on 2006-10-03, modified on 2017-05-12

In the context of future accelerators and, in particular, the beam vacuum of the Large Hadron Collider (LHC), a 27 km circumference proton collider to be built at CERN, VUV synchrotron radiation (SR) has been used to study both qualitatively and quantitatively candidate vacuum chamber materials. Emphasis is given to show that angle and energy resolved photoemission is an extremely powerful tool to address important issues relevant to the LHC, such as the emission of electrons that contributes to the creation of an electron cloud which may cause serious beam instabilities and unmanageable heat loads on the cryogenic system. Here we present not only the measured photoelectron yields from the proposed materials, prepared on an industrial scale, but also the energy and in some cases the angular dependence of the emitted electrons when excited with either a white light (WL) spectrum, simulating that in the arcs of the LHC, or monochromatic light in the photon energy range of interest. The effects on the materials examined of WL irradiation and /or ion sputtering, simulating the SR and ion bombardment expected in the LHC, were investigated. The studied samples exhibited significant modifications, in terms of electron emission, when exposed to the WL spectrum from the BESSY Toroidal Grating Monochromator beam line. Moreover, annealing and ion bombardment also induce substantial changes to the surface thereby indicating that such surfaces would not have a constant electron emission during machine operation. Such characteristics may be an important issue to define the surface properties of the LHC vacuum chamber material and are presented in detail for the various samples analyzed. It should be noted that all the measurements presented here were recorded at room temperature, whereas the majority of the LHC vacuum system will be maintained at temperatures below 20 K. The results cannot therefore be directly applied to these sections of the machine until measurements at cryogenic temperatures, i.e., in the presence of cryosorbed gas layers, are obtained. However, these results are directly relevant to all the warm regions of the LHC vacuum system, such as the experimental vacuum chambers and warm element vacuum chambers in the insertion regions.

The scale control challenges for two North Sea carbonate reservoirs are reviewed in this paper. Whilst carbonate reservoir are not the largest source of hydrocarbon within the North Sea, they are very significant on a global bases.The mechanism of scale inhibitor chemical retention observed for phosphonate, polymer, and vinyl sulphonate co-polymer inhibitors on carbonate reservoir substrates is outlined. Chemical placement represents the most significant technical challenge when performing scale squeeze treatments into fractured chalk reservoirs. Examples from over 50 field treatments applied in reservoirs E and V, where both phosphonate and vinyl sulphonate polymer chemicals have been deployed, are used to illustrate the difference in chemical retention observed in laboratory evaluations. The laboratory studies demonstrated clear potential for significant extension in treatment lifetime by changing from a phosphonate to a vinyl sulphonate co-polymer-based scale inhibitor. The selection and qualification of chemical placement systems for deployment of inhibitors in fractured carbonate reservoirs are also outlined. To this end, novel technologies to enhance conventional scale inhibitor chemical placement are vital to economic success during water flood projects.

We discuss the predicted electron cloud build up in the arcs and the long straight sections of the LHC, and its possible consequences on heat load, beam stability, long-term emittance preservation, and vacuum. Our predictions are based on computer simulations and analytical estimates, parts of which have been benchmarked against experimental observations at the SPS.