Experimental viscosity and density data of four natural gases are presented for temperatures from 100 to 340 F and pressures from 100 to 8,000 psia. A correlation is discussed and results reported. Introduction This investigation is one of several efforts by the authors to provide viscosity data for pure hydrocarbons and mixtures. Results of some pure hydrocarbons and their mixtures have been presented. Several predictive methods and correlations have also been reported. This paper presents the experimental viscosity and density data of four natural gases and confirms a correlation in a previous study. APPARATUS The viscometer was described previously. A bank of stainless steel pycnometers was included to determine density in conjunction with the viscosity measurements (Fig. 1). DATA AND MATERIALS The natural gases were furnished by the Atlantic Richfield Co. (Samples 1 and 2), the Continental Oil Co. (Sample 3) and the Pan American Petroleum Corp. (Sample 4). Table 1 shows the composition of these gases obtained by mass spectrometer analysis. The pure component viscosity data used in the correlation have been published. Experimental and calculated viscosity data for the natural gases are presented in Tables 2 through 5. CORRELATION Starling and Ellington have reported several semi-empirical expressions based to a certain extent on the theory of viscosity advanced by Born and Green. The final expression presented by Starling and Ellington is: (micropoise)= o exp[X(T) pY(T)]....... (1) Eq.1 was modified by Lee et al. to represent mixture and pure component data simultaneously. This equation has the form: ..........(2) where K= ..........(3) X= ..........(4) Y= ..........(5) Over the pressure and temperature range studied in this investigation, this equation represents the data on methane, ethane, propane, n-butane and four methane-n-butane mixtures with a standard deviation* of 1.89 per cent. Density data by Sage and Lacey were used to fit the equations. Eq. 2 gives reliable values of the viscosity of light hydrocarbons without prior knowledge of experimental viscosity values, but accurate density data must be available. Eq. 2 was used to predict viscosity values for the natural gases studied in this paper. The particular set of parameters contained in Eqs. 3 through 5 gave values that reproduced experimental data within 5 per cent. Needless to say, in using Eq. 2 better density values will give better viscosity results. However, those engineers who do not have accurate density values at hand or the time, or such facilities as a library. computer, etc. readily available, may feel uneasy in using Eq. 2. Therefore, the authors sought the easiest but by no means best density prediction method, which was reported by Kay 30 years ago. A set of density values, which were calculated based on Kay's method, and a generalized compressibility factor chart were used to fit Eq. 2. JPT P. 997ˆ

This study compares the results of two laparoscopic hernioplasties: the transabdominal preperitoneal (TAPP) and the totally extraperitoneal (TEP). Over a 43-month period 1,115 laparoscopic hernioplasties, 733 TAPP and 382 TEP, were performed in 866 patients. There were 11 major complications in the TAPP group (2 recurrences, 6 trocar hernias, 1 small-bowel obstruction, 1 trocar, and 1 dissection injury of the small bowel) compared to 1 recurrence and no intraperitoneal complications in the TEP group. Five TEP procedures required conversion to the TAPP approach, resulting in one umbilical hernia. The median time to return to work did not vary with the approach, but was prolonged in patients compensated for time off, 16 vs 8 days for noncompensated patients. Results suggested that both techniques shortened recovery and eliminated most early failures, but the totally extraperitoneal approach reduced the potential for intraperitoneal complications and may be the procedure of choice in most situations.

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