SummaryReservoir risk management involves optimizing assets given inherent reservoir uncertainties and minimizing risk by reducing these accordingly. The decision to implement any reservoir management technology is usually based on some form of cost-benefit analysis. Consequently, the correct valuation of value-adding technology (often based on net present value, or NPV) becomes a significant part of a reservoir management process. This paper discusses techniques for the valuation of technology and information related to reservoir risk management. For demonstration purposes, these techniques are applied to valuation of real-time control and monitoring technologies in a reservoir with multiple uncertainties in its physical properties. Because of the presence of these uncertainties, value quantification requires a stochastic optimization of the reservoir production strategy, where the objective function includes a risk-aversion factor. By applying these techniques, one can generate a decision-making table that shows the benefit of implementing a technology at various confidence levels. One can then extend the analysis further to estimate the added value to the reservoir if the uncertainties were to be reduced (or even eliminated) by implementing appropriate monitoring technologies. This process enables quantification of the value of information and is useful in designing monitoring strategies.

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We were interested to read the account of three severe cases of compartment syndrome following the use of the Lloyd-Davies position for laparotomy (Turnbull & Mills. Anaesthesia 2001; 56: 980–7) and the response in your correspondence section (Kaufman & Hawley. Anaesthesia 2002; 57: 188). Over the past 20, years we have managed over 1000 patients who have been placed in Lloyd-Davies position for major gynaecological oncology surgery. We have never seen a case of compartment syndrome in that time. The paper therefore raises many unanswered questions. It might be that the duration of surgery (over 4 h) in these cases was a major factor, but our cases have frequently exceeded this␣time, especially for anterior and posterior excenterations. All three cases that had a problem were given a thoracic epidural and the significant changes that such an intervention may produce in terms of peripheral and central vascular tone may have some bearing on the outcome. There are a large number of unknown variables in cases such as these. These variables include the angle of abduction into which the legs are placed, the degree of intra-operative hypotension experienced by the patient (in addition to any effects of the epidural), the degree to which the legs are elevated and the method of fixation of the legs. All of these may have an effect on leg muscle perfusion. In addition, there is a tendency for assistants in the surgical operation to stand between the␣abducted legs and rest their arms on the patients' legs, especially during prolonged surgery in the abdomen. This must have a deleterious effect on leg muscle perfusion and re-perfusion. To our mind, the much greater concern was the view expressed by the authors that it may be safer to dispense with calf compression stockings and intermittent calf compression devices when the Lloyd-Davies position is used. We believe that such advice is not warranted in a high-risk group with pelvic or abdominal cancers on the basis of three very unfortunate cases. The risks of deep vein thrombosis and pulmonary embolus is, we would suggest, a much greater risk than compartment syndrome in these cases and we would advocate the use of graduated compression stockings and calf compression to assist in fluid drainage from the legs. In summary, we feel that Turnbull and Mills have highlighted a very unfortunate sequaelae of operating in the Lloyd-Davies position in three cases. They have not provided convincing reasons to change ‘normal practice’ in the use of calf compression devices and we would urge caution in the adoption of their recommendations based on a 20-year history of surgical and anaesthetic practice without this complication.

We would like to comment on the study by Bucx and colleagues regarding the effects of autoclaving on the performance of fibrelight laryngoscopes (Anaesthesia 1999; 54: 875–8). They rightly suggest that this is an area that has been little studied and their findings raise doubts about recommending routine autoclaving for some of the blades they tested due to degradation of the light-guide. In one of the hospitals in which we work, the current practice of routine autoclaving is now being questioned for precisely this reason. In our national survey of practice and attitudes to laryngoscope decontamination [1], the issue of cost was raised by a number of departments. To autoclave between each case requires a large stock of blades, and clearly some of these light-guides would require regular replacement if the results of this study are typical. In any case, most departments do not have guidelines regarding laryngoscope decontamination, and in some that do, compliance with guidelines is variable. The authors suggest that steam sterilisation can overcome a number of problems with laryngoscope decontamination, but others do remain. Implementing guidelines requiring routine autoclaving may not be straightforward (particularly in the light of their results), and autoclaving is ineffective against prion diseases, one of which has been isolated from tonsillar tissue [2]. There are alternative approaches to the problem, including disposable single-use blades and sheaths. In the same edition of Anaesthesia as this study, an advertisement appeared for single-use blade sheaths. However, our survey found that some anaesthetists and operating department assistants do not consider laryngoscope decontamination or sterilisation to be necessary, and to them ‘social cleanliness’, such as that you would expect of cutlery in a restaurant, would appear to be an adequate aim of treatment. There is, as yet, no consensus view on what constitutes adequate laryngoscope blade and handle treatment between uses. This valuable study gives further support to Skilton's view [3] that national guidelines are needed regarding the care of laryngoscopes.

Abstract It has become customary to compute pressure transient model solutions in the Laplace domain. This is because it generally simplifies the solution, and allows easy incorporation of wellbore storage, commingled systems or dual-porosity formations. On the other hand, the convolution and parameter estimation are usually done in the time domain. Thus, when the solution is used as the forward model in an optimization scheme, each forward evaluation requires a Laplace inversion of the model (using the Stehfest algorithm) and a time domain convolution. Here we explore the alternative of transforming the data into the Laplace domain (a one-time operation) and then doing the fitting in the Laplace domain. The chief new result is a self-consistent prescription for dealing with the fact that the data are available only over a finite time interval. The technique is illustrated for the case of a conventional well test which reaches radial flow on the time scale of the test, a situation for which the method is particularly efficient.

Summary Curare was used in the 19th century in England by a wide variety of scientists, physicians and veterinarians. Their experiments indicated many of the properties of the drug, but its clinical usage remained very limited and was reserved for cases of tetanus, hydrophobia and strychnine poisoning. Griffith and Johnson are usually credited with the introduction of curare into clinical anaesthesia in 1942, but a Dr F.P. de Caux working at the North Middlesex Hospital, London, in 1928 utilised curare in a series of seven patients. His work was not widely publicised and this contribution to anaesthetic history has been overlooked by subsequent authors.

Summary New analytic solutions are presented in real time and as Laplace transforms for horizontal wells in reservoirs bounded at the top and bottom by horizontal planes. Two types of boundary conditions are considered at these planes, and the Laplace-transform pressure solutions are used to include wellbore-storage and skin effects. Solutions are based on the uniform-flux, line-source solution, but differ from most existing solutions owing to the use of pressure averaging to approximate the infinite-conductivity wellbore condition and use of the correct equivalent wellbore radius for an anisotropic reservoir. New flow periods (regimes) are identified, and simple equations and existence criteria are presented for the various flow periods that can occur during a transient test.

Summary When a horizontal well is selectively completed, the productive length maynot be the entire drilled length of the horizontal section. The productivity ofthe well will be affected by the total length and productivity of the well willbe affected by the total length and distribution of the open intervals. Thispaper presents a method to calculate the inflow performance of a horizontalwell that is selectively completed. Introduction Completion of horizontal wells as open holes or with slotted (Figs. 1a and 1b) leaves operators with little or no opportunity to perform diagnostic orremedial work. perform diagnostic or remedial work. Many horizontal wells thathave been producing for several years are now producing for several years arenow experiencing production problems that can be attributed to the lack ofcompletion control. This is particularly true in areas where the targets arethin and coning n a potential problem. It is inevitable that certain portionsproblem. It is inevitable that certain portions of the well will be closer tothe fluid/fluid contact than others and that hydraulic isolation of thoseportions would significantly improve long-term performance. Also, when drillingcontrol or sufficient geological knowledge is absent, portions of the well maynot even lie within the reservoir. Considerable knowledge has been developed onhow to complete horizontal wells successfully; what is missing is a method forpredicting the performance of different completion strategies. It may be thatit is not practical or cost effective to open the entire practical or costeffective to open the entire length of the well within the reservoir. Figs. 1c and 1d are schematics of a selectively completed well. The well in Fig. 1c was completed with external casing packers (ECP's) that had alternate slotted andunslotted sections. Fig. 1d shows that the same effective completion wasachieved with a cemented liner that was subsequently perforated. For thepurpose of inflow perforated. For the purpose of inflow calculations, thesecompletions are identical. As horizontal well technology has developed, severalinflow performance formulas for horizontal wells have been discussed in theliterature. In this paper, we expand the work of Goode and Kuchuk to includethe effects of having only a portion of the well open. They present a solutionfor the inflow performance of a horizontal well producing from a reservoir ofuniform producing from a reservoir of uniform thickness within a closed, rectangular drainage region. The well can be placed arbitrarily within thedrainage volume, provided that the distance from any part of the well (open toflow) to a lateral boundary is large compared with the scaled of the reservoir. In practice this is not an unduly restrictive assumption, unless the verticalpermeability is extremely low. It is much less permeability is extremely low. It is much less restrictive than the geometry required by Giger el al. and Karcher el al, where the well must be short enough, compared with the boundedregion, to permit the development of radial flow before the effect of thelateral boundaries is felt. The formulas presented by Babu and Odeh and Goodeand Kuchuk are for a well placed inside a drainage volume with no flux crossingany external boundary, while the formulas presented in Refs. 3 through 5 assumea constant pressure at the external lateral boundaries and no-flux conditionsat the top and bottom. The no-flux condition on all external boundaries is themost relevant for practical purposes and is the boundary condition used in thiswork. Mathematical Model We consider a horizontal well of length 2L 1/2 centered at (x w, y w, z w)and producing from a rectangular region of dimensions Lx and Ly, through n popen intervals, with Segment i of length 2L i centered at x i (Fig. 2). Thedistribution and number of open interviews is arbitrary, as is the position ofthe well within the drainage area, provided that the distance from any openinterval to a lateral is large compared will the scaled reservoir thickness h(kx/k z) 1/2. With this restriction, the pressure will be vertically equilibratedbefore the influence of any lateral boundaries is felt, and we may derive theinflow formula by writing the pressure drop as a sum of two terms. We firstpressure drop as a sum of two terms. We first consider a 2D fracture problemthat is analogous to the horizontal well problem at long times. We then accountfor the pressure drop in the third dimension, z, by including a pseudoskin, SzD, determined by solution of pseudoskin, S zD, determined by solution of a 3Dproblem (not 2D as in Refs. 3 through 5) that excludes the lateral boundaries. The inflow performance of a well is related to the long-time behavior of theconstant-rate pressure. At long times, when no flux is permitted to cross theexternal boundaries, the difference between the average pressure in thereservoir and wellbore pressure pressure in the reservoir and wellbore pressureapproaches a constant value that we call the inflow pressure. JPT P. 983

A case of Moya-moya disease requiring anaesthesia for both investigation and attempted surgical correction is presented. The influence of the anaesthetic technique on the abnormal cerebral vasculature, with particular reference to induced hypocapnia, is discussed. Guidelines for a safe method of anaesthesia in this group of patients are suggested.

AnaesthesiaVolume 40, Issue 11 p. 1144-1144 Free Access New tubes for old D.J. Wilkinson, D.J. Wilkinson Department of Anaesthesia, St Bartholomew's Hospital, London EC1A 7BESearch for more papers by this author D.J. Wilkinson, D.J. Wilkinson Department of Anaesthesia, St Bartholomew's Hospital, London EC1A 7BESearch for more papers by this author First published: November 1985 https://doi.org/10.1111/j.1365-2044.1985.tb10645.xAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onEmailFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume40, Issue11November 1985Pages 1144-1144 RelatedInformation

AnaesthesiaVolume 39, Issue 1 p. 72-72 Free Access Measurement of blood loss in children D.J. Wilkinson, D.J. Wilkinson Department of Anaesthesia, St Bartholomew's Hospital, London, EC1Search for more papers by this authorJ. Redmond, J. Redmond Department of Anaesthesia, St Bartholomew's Hospital, London, EC1Search for more papers by this author D.J. Wilkinson, D.J. Wilkinson Department of Anaesthesia, St Bartholomew's Hospital, London, EC1Search for more papers by this authorJ. Redmond, J. Redmond Department of Anaesthesia, St Bartholomew's Hospital, London, EC1Search for more papers by this author First published: January 1984 https://doi.org/10.1111/j.1365-2044.1984.tb09474.xAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL No abstract is available for this article. Volume39, Issue1January 1984Pages 72-72 RelatedInformation

In 1971, Maroteaux et al. described a type of short-limbed dwarfism in which the shortening predominantly affected the forearms, hands, legs and feet, and which they named “acromesomelic dwarfism”. They reported three patients: two sisters examined at four and 13 years of age and again at 19 and 28 years, and one adult male. They established that this dysplasia could be distinguished radiologically from other causes of short-limbed dwarfism. Acromesomelic dwarfism remains a rarely reported osteochondrodysplasia with only 20 reported cases. We report a further case of this syndrome, the first to be observed in the United Kingdom. Patient was born on 2.8.67 at 36 weeks' gestation, when he weighed 3.09 kg. The parents are normal, though the father is of short stature; no family history of dwarfism is present. His mother thought something was wrong with the child within a few days of birth. She considered his arms too short and he was generally out of proportion. She was told that the child was achondroplastic. Feeding difficulties occurred in the early months due to nasal obstruction, but weight gain was satisfactory and milestones occurred normally. At twelve months he was walking and his intellectual and mental functions appeared normal. In 1972, at the age of four, a diagnosis of mucopolysaccharidosis IV was considered, but the urinary level of keratan sulphate was normal. A chromosome analysis at this time revealed a normal karyotype 45XY. At this age his height and weight were below the third percentile at 70 cm and 12.8 kg.

Two cases of intestinal duplication occurring in neonates are described, the first a gastric duplication, the second a rectal duplication, both diagnosed radiologically before operation. These sites are uncommon as this lesion is most frequently associated with the ileum or oesophagus. The gastric duplication was attached to the greater curvature with a small intrathoracic extension. It did not communicate with the stomach. The child presented at two weeks with signs of an upper intestinal obstruction. A plain film and barium meal snowed a large, soft tissue mass with the shape of a full stomach in the left hypochondrium displacing the stomach to the right. An IVP was normal. The rectal duplication presented at one month with constipation and a prolapsing cystic mass. A barium enema showed the extent of the lesion and a cyst puncture that it did not communicate with the intestine. An X ray of the lumbar spine and sacrum did not show an associated defect.