Application to Petroleum Engineering of Statistical Thermodynamics – Based Equations of State

International audienceCubic equations of state (EOS) have proven their utility to the petroleum engineers for many decades. Their predictive power remains, however, limited. Statistical mechanical approaches have meanwhile grown allowing the development of powerful engineering equations of state. In particular, this paper investigates how equations that are based on the association term of Wertheim can improve significantly the predictive power in petroleum applications. Three distinct issues are discussed. Mixtures of associating components such as water or methanol with hydrocarbons have so far represented one of the main challenges for the predictive power of equations of state. It is shown that the CPA equation, that combines the classical SRK EOS with the association term of Wertheim, provides a significant improvement for both methanol-hydrocarbon and water-hydrocarbon mixtures. The physical significance of the SAFT parameters makes it possible to develop a group contributions method for their determination. Using this approach, it becomes possible to predict vapour pressure and liquid volume of heavy molecules. This is shown for a number of families, such as n-alkanes, n-alcohols, 1-olefins as well as for isomers of methyl-alkanes. Finally, the improved predictions resulting from the use of polar terms with SAFT are illustrated. The effect of the quadrupole is clearly shown with an aromatic-non aromatic mixture. Including a dipolar interaction makes it possible to differentiate the behaviour of the cis and the trans 2-butene isomers

La transplantation hépatique chez l'enfant.

Liver transplantation has become a clinical therapeutic modality for end stage liver diseases. The results achieved in children are better than in adults: in T.E. Starzl unique experience in Pittsburgh, USA, the survival rate at one and four years are 75 and 70% respectively. Complete rehabilitation of these children can nowadays be expected. Between March 1984 and June 1985, 8 children received an orthotopic liver transplantation at the University of Louvain Medical School in Brussels, Belgium; one child received two transplantations after acute and irreversible rejection of a first ABO incompatible graft. The indications were biliary atresia in five (polysplenia in one), biliary hypoplasia in one, alpha-1-antitrypsine deficiency in one and Crigler-Najjar syndrome type I in one. The age of the patients at the time of liver replacement was 12 to 18 months in four, 8 to 13 years in four. Six patients are alive after 17, 14, 12, 10, 3 and 3 months; the two youngest children deceased during the first postoperative month. The Kaplan-Meyer one year survival rate is 75%; all surviving children are in excellent clinical condition with a normal liver function. The 9 transplanted livers were harvested from multiorgan cerebral death donors with the exception of one neonate whose liver alone was removed; 4 were retrieved locally, the five others were offered by foreign hospitals through the organ procurement agencies (Eurotransplant, France-Transplant, U.K. Transplant). Due to appropriate logistics with air flight transportation of the harvesting team when indicated, the total ischaemia time was kept below 6 hours in every case. Two small children underwent a left lobe orthotopic transplantation after ex vivo right trisegmentectomy of the liver retrieved from an older donor with one long term survival. The indications for liver transplantation in children are end-stage liver diseases consisting of a) cholestatic diseases among which the most frequent is biliary atresia after unsuccessful Kasai procedure followed by familial cholestasis (Byler syndrome) and the paucity of the intrahepatic bile ducts of the syndromatic (Alagille syndrome) or non syndromatic type. b) the metabolic diseases resulting either in cirrhosis with liver failure (alpha-1-antitrypsin deficiency, Wilson disease, glycogen storage disease type I and IV, protoporphyria) or in extrahepatic complications of enzymatic deficiency of an otherwise normally functioning liver (Crigler-Najjar syndrome type I, familial hypercholesterolemia and perhaps oxalosis). c) the hepatocellular diseases either chronic with cirrhosis of various origin or acute, eg. toxic hepatitis.(ABSTRACT TRUNCATED AT 400 WORDS