Treating optical density data for fluid sample comprises obtaining data in both chromatic and component channels and eliminating chromatic absorption from optical density measurements

摘要

A chromatic absorption function for the fluid sample is determined from the optical density data in the chromatic channel. Part of the optical density in the fluid component channel(s) is determined from the chromatic absorptions. The data for the component channel(s) is corrected by eliminating the part of the optical density in the component channel(s) caused by chromatic absorption : The chromatic channel contains at least two chromatic channels and the chromatic absorption function contains two unknowns. To determine the chromatic absorption function, calculating the part of the optical density caused by chromatic absorptions and chromatic correction are done on optical density data received at a number of instants. The chromatic absorption function depends on the wavelength of the incident light. The fluid component channel includes a methane channel, an oil channel, or a channel containing both methane and oil, and the process also includes calculation of the gas-oil ratio and the percentage contamination of the fluid sample. Optical density data is also obtained for a fluid sample in a base channel and the part of the optical density caused by chromatic absorption in the base channel is calculated from the chromatic absorption function. The diffusion of the optical density data for the component channel(s) is corrected by eliminating the optical density of the base channel from the optical density of the component channel(s). The measurements are repeated for a water channel to allow calculation of a water-absorption ratio for the fluid component channel and the correction of optical density data in the fluid component channel by eliminating the optical density absorption due to water. These calculations are repeated at a number of instants and the water-absorption ratio is determined by experiment. The fluid component channel contains methane, oil, or both. An independent claim is for an electronic system for carrying out the above process, comprising an inlet device to receive optical density data for a fluid sample at a number of instants; a memory connected to the inlet device to record the data received, a processor coupled to the memory and designed to use the optical density data to develop a system of equations to model the optical density in each channel in the form of a sum of at least two elements of the following: chromatic absorptions, absorptions due to molecular vibrations, absorptions due to water and diffusion, and designed to resolve the system of equations to determine the absorptions due to the molecular vibrations in a channel of methane and a channel of oil. The electronic system is connected to or integral with a sampling device for a base fluid.