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Description:
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The densities of three different natural gas mixtures (Case A , Case B , and Case C ) were evaluated at pressures from 14 to 38 MPa (2000 to 5500 psia ) and temperatures from 230 K to 350 K by using SonicWare ? and NIST -14 software packages . The chosen pressures and temperatures were based on the phase diagrams for each composition and the probability of encountering such conditions in reservoir or pipeline environment . For each isotherm , the heaviest hydrocarbon was varied from 0 to 1 mole percent in increments of 0 .001 (Dx=0 .001 ) and the density calculated for each composition . After the densities were obtained , the partial derivatives of the densities with respect to composition , were calculated numerically at fixed pressure and temperature .
The results and calculations suggest that it is very difficult to obtain the desired accuracy (+ 0 .1 % ) in densities when using a combination of composition measurements and equation of state calculations . |