Patent ID: 8332194

Claim:
A method of performing production operations of an oilfield having at least one process facility and at least one wellsite operatively connected thereto, each at least one wellsite having a wellbore penetrating a subterranean formation for extracting fluid from an underground reservoir therein, the method comprising: obtaining, during operation of a separator, a sample of separator discharge fluid from the separator, wherein the separator is (a) receiving separator inlet fluid extracted from the underground reservoir and (b) separating oil, gas, and water from the separator inlet fluid to produce the separator discharge fluid; performing gas chromatography on the separator discharge fluid to obtain gas molar composition; performing oil characterization on the separator discharge fluid to obtain oil density and oil molecular weight; and determining, during operation of the separator and without accessing the separator inlet fluid, composition of the separator inlet fluid by: performing a first simulation of the separator based on the gas molar composition, the oil density, the oil molecular weight, and a gas oil ratio (GOR) of the separator discharge fluid to obtain a first simulated composition value of the separator inlet fluid, wherein the first simulation is performed using a simulator; performing a second simulation of the separator based on the first simulated composition value of the separator inlet fluid to obtain a second simulated composition value of the separator discharge fluid, wherein the second simulation is performed using the simulator; comparing the second simulated composition value of the separator discharge fluid and an actual composition value of the separator discharge fluid to generate a difference, wherein the actual composition value of the separator discharge fluid is obtained from the sample; and presenting the first simulated composition value of the separator inlet fluid, when the difference is less than a threshold value.