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Method for Testing Rate of Gas Diffusion in Crude Oil by Periodic Measurement of Concentration Profiles.

Authors
Brow-GT; Cupps-CQ; Fry-JJ
Source
NTIS: PB 190 967 :22 pages
Link
NIOSHTIC No.
10008959
Abstract
An experimental method is described for testing diffusion of gases in crude oils at pressures and temperatures up to 3,000 psia and 200 deg. F. A sampling technique was developed to withdraw by constant- pressure mercury displacement about 60 ul of oil from the diffusion cell through any of several 1/2-inch vertically spaced capillary tubes and to trap about 4 ul of the oil in a specially designed microsampler. Oil trapped in the microsampler can be completely inserted in the sample inlet of a chromatograph. From analysis in a three-stage chromatograph (GLC), gas concentration in a sample is determined from the ratio of gas peak heights to area of peaks of reference components (hexanes or heptanes) in the oil. A diffusion coefficient is calculated from measured concentration profiles with known equations for diffusion in finite or semi-infinte systems, depending on whether the gas has or has not reached the end of the oil column. Results are given for a test of methane diffusing at 2,560 psia and 160 deg. F. In crude oil from the weber sandstone reservoir in the rangely field, Colorado. A constant diffusion coefficient of 3.34 X 10-5 cm2 per second was obtained which gives a good fit between calculated and experimental profiles determined at six times after start of diffusion. The maximum standard error of gas concentration determinations experienced with this method was +- 0.88 Ml per ml of gas-free oil. Work done in cooperation with the University of Wyoming.
Publication Date
19700101
Document Type
IH; Report of Investigation;
Fiscal Year
1970
NTIS Accession No.
PB-190967
NTIS Price
A03
Identifying No.
RI 7359
NIOSH Division
LERC;
Source Name
NTIS: PB 190 967
State
CO; WY;
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