Huffs method

Once it has been checked that the method is applicable (see A5.2.1 above) the relief size can be evaluated as follows  

evaluate the mass remaining in the reactor at the maximum accumulated pressure  

A worked example of the use of Huffs method is given below. 

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There are two versions of Huffs method. The original and more rigorous method is described in reference 1 It requires iteration to find a solution and, therefore, takes longer to evaluate than the simplified method given below[2) for little increase in accuracy... 

Steam is injected into a reservoir to reduce oil viscosity and make it flow more easily. This technique is used in reservoirs containing high viscosity crudes where conventional methods only yield very low recoveries. Steam can be injected in a cyclic process in which the same well is used for injection and production, and the steam is allowed to soak prior to back production (sometimes known as Huff and Puff). Alternatively steam is injected to create a steam flood, sweeping oil from injectors to producers much as in a conventional waterflood. In such cases it is still found beneficial to increase the residence (or relaxation) time of the steam to heat treat a greater volume of reservoir. 

Another method of using CO2 is called cycHc CO2 stimulation or huff n puff (26). A limited amount of CO2 is iajected into a reservoir over hours or days. The well is then shut in for a soak period of days to weeks to allow the CO2 to interact with the cmde oil, swelling the oil and reducing its viscosity. 

Secondary recovery, infill drilling, various pumping techniques, and workover actions may still leave oil, sometimes the majority of the oil, in the reservoir. There are further applications of technology to extract the oil that can be utilized if the economics justifies them. These more elaborate procedures are called enhanced oil recovery. They fall into three general categories thermal recoveiy, chemical processes, and miscible methods. All involve injections of some substance into the reservoir. Thermal recovery methods inject steam or hot water m order to improve the mobility of the oil. They work best for heavy nils. In one version the production crew maintains steam or hot water injection continuously in order to displace the oil toward the production wells. In another version, called steam soak or huff and puff, the crew injects steam for a time into a production well and then lets it soak while the heat from the steam transfers to the resei voir. After a period of a week or more, the crew reopens the well and produces the heated oil. This sequence can be repeated as long as it is effective. 

In 1972 a paper on venting by Huff 2J documented concerns that many designers suspected that to truly be safe the vent sizing of many systems should be based on assuming two-phase flashing flow in the vent system. A two-phase flow vent method developed by Huff was compared with Boyle s all-liquid method, and values from the FIA chart in Figure 2. It can be seen that under many conditions, previous methods were not... 

Williams, D.C., Huff, G.F., and Seitz, W.R. (1976) Glucose oxidase chemiluminescence measurement of glucose in urine compared with the hexokinase method. Clin. Chem. 22, 372. 

A specific problem can be approached in two ways (1) use the design charts presented by First and Huff [232]. and (2) use the VSP package and calculation methods [195]. 

Note The outline presented by Pierson is, based on the method of W. Huff, M. Halik l F. Pristera described in PATR 2472 (Dec 1957) of the Feltman Research Laboratories, Picatinny Arsenal, Dover, NJ and also on the paper of F. Pristera (of PicArsn) in Applied Spectro-j scopy 7, 115 (1953) (See also Ref 18, pp7-9) Analysis of Wrapper for paraffin, NG, paper] ash, and moisture is described in detail, by Pierson (Ref 11, pi364) [... 

As the mixture ratio approaches stoichiometric proportions, the dissociation products become more important and the distinction between maj or and minor products becomes indistinguishable. In this range of mixture ratio, one needs more refined analytical techniques than that just described. A method due to Huff < / af (22) will be described and is particularly appropriate for digital machine computation. 

In order to show the procedure, the method will be adapted to the case where an initial temperature estimate is made and the problem is to find the product composition. Using the nomenclature of Huff, one can write any chemical equation as follows ... 

Cox, J. D. and Pilcher, G. Thermochemistry of Organic and Organo-metallic Compounds, Academic Press, London 1970 Huff, V. N Gordon, S. and Morell, V. . General method and thermodynamic Tables for Computational of Equilibrium Composition and Temperature of Chemical Reactions, NASA Report 1073 (1973) Gordon, S. and Bride, B. J. Computer Program for Calculation of Complex Chemical Equilibrium Compositions, Rocket Performance, Incident and Reflected Shocks and Chapman-Jouguet Detonations, NASA Report SP-273 (1971)... 

H. Seiter, Integrational etching methods, in Semiconductor Silicon 1977, H. R. Huff and E. Sirtl (eds.), p. 187, Electrochemical Society, Permington, 1977. 

Kolbert, A. C., Carroll, C. A. and Huff, L. A. Nuclear magnetic resonance in pharmaceutical development. In Biopharma Guide to Analytical Methods (in press). 

In the majority of treated wells at Zybza Held, the amount of additional oil produced upon repetition of the steam soak showed a decrease from the amount of additional oil produced during the first treatment. In this study, the steam soak was systematically repeated over an extended period of time on 30 oil wells. The aim was to determine the ultimate effectiveness of a treatment restricted to the near bottomhole zone, and to determine the maximum final recovery of oil by this method. Altogether 73 individual "huff and puff" treatments were carried out in seven cycles. Not all of the 30 wells were treated during each successive cycle (Table 16). 

Table 18 and Rgurc 37 show that during the 3-year period of steaming by huff and puff method, on the average, about 5,0001 of oil was produced annually. During that time 10,0001 of steam was injected, resulting in a steam/oil factor of only 0.7. 

If, however, the ab-initio calculation of a specific molecule jdelds the complete potential energy hypersurface (as discussed above) the FG-matrix method (7) can be used. This was done by, e.g. AUavena (52), Hartmann and Gliemann (55) and Menna, Mocda and Randaccio (44). Huff and Ellison (144) present an easier and simpler method which is very favourable for computational purposes it also depends on truncating the potential after the harmonic term the 3 N mass-weighted (mi) Cartesian displacement co-ordinates Axi are called qi, and are given by... 

V. N. Huff, S. Gordon, and V. Morrell, General Method and Thermodynamic Tables for Computation of Equilibrium Composition and Temperature of Chemical Reactions, NASA Report 1037 (1951). 

Basically, four main areas of methods for gear fault detection have been published. Signal processing techniques. Statistical analysis (ANDRADE, ESAT, BADI, 2001 BAYDAR eta/., 2001 TUMER HUFF, 2003 HE, KONG, YAN, 2007), Time-series analysis (ZHAN JARDINE, 2005 ZHAN, MAKIS, JAR-DINE, 2006) and Artificial neural networks AYA ESAT, 1997 SAMANTA, 2004 SANZ, PERERA, HUERTA, 2007 RAFIEE et cd., 2007). 

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