US 12,140,585 B2
Estimating molecular weight of hydrocarbons
Omer Refa Koseoglu, Dhahran (SA); and Saroj Kumar Panda, Dhahran (SA)
Assigned to Saudi Arabian Oil Company, Dhahran (SA)
Filed by Saudi Arabian Oil Company, Dhahran (SA)
Filed on Jul. 15, 2021, as Appl. No. 17/376,540.
Prior Publication US 2023/0026355 A1, Jan. 26, 2023
Int. Cl. G01N 33/28 (2006.01); G01N 21/359 (2014.01); G16C 20/30 (2019.01); B01J 20/291 (2006.01); G01N 9/36 (2006.01); G01N 21/31 (2006.01)
CPC G01N 33/2823 (2013.01) [G01N 21/359 (2013.01); G16C 20/30 (2019.02); B01J 20/291 (2013.01); G01N 9/36 (2013.01); G01N 2021/3155 (2013.01)] 7 Claims
OG exemplary drawing
 
1. A method for estimating a molecular weight of a hydrocarbon fluid, comprising:
measuring a density of the hydrocarbon fluid;
obtaining a near infrared (NIR) spectrum of the hydrocarbon fluid;
calculating an index value (NIRA) for the hydrocarbon fluid from the NIR spectrum, wherein the NIRA is calculated from the equation:

OG Complex Work Unit Math
wherein absorbance is an absorbance value of the hydrocarbon fluid at each wavenumber (cm−1) between 4,000 cm−1 to 12,821 cm−1;
calculating an estimated molecular weight from the equation:
Molecular Weight=Constant+X1*DEN+X2*DEN2+X3*DEN3+X4*Index+X5*Index2+X6*Index3+X7*DEN*Index,
wherein X1, X2, X3, X4, X5, X6, and X7 are coefficients determined by a statistical analysis correlating molecular weight of the hydrocarbon fluid with density and NIR spectrum, Constant is a constant determined by the statistical analysis, DEN is the density value, and Index is the index value; and
providing the estimated molecular weight as an output.