Quantitative identification of hydrocarbon concentration in drilling fluid based on laser Raman spectroscopy

The hydrocarbons in the drilling fluid can indicate the hydrocarbon content of the formation.The detection of oil and gas concentration in the stratum is of great significance for the identification of true and false oil and gas, especially for the accurate interpretation and evaluation of oil and gas layers.Based on the unique advantages of continuous, rapid and direct detection of samples by laser Raman spectroscopy, we carried out researches on quantitative Raman detection of hydrocarbon concentration in drilling fluid.The laser Raman online detection system was built under laboratory conditions which was used to detect C₇-C₁₄ normal paraffin and benzene.The n-octane was selected as the marker of alkanes in water-based drilling fluid and the mathematical models of different characteristic peaks of n-octane in water-based drilling fluid were established based on the least square method.The vibration intensity at the frequency shift of 1 298 cm^-1 has a good linear relationship with n-octane content.The benzene was selected as the marker hydrocarbon in the diesel oil drilling fluid and the mathematical model of different characteristic peaks of benzene in oil drilling fluid were established based on the least square method.The vibration intensity at the frequency shift of 986 m^-1 has a good linear relationship between the vibration intensity and the content of added benzene.The experimental results show that the laser Raman spectroscopy can be used for in-situ detection of hydrocarbon concentration in drilling fluid and has good stability and repeatability in order to provide a new way for the inversion of oil and gas concentration and improving the accuracy of oil and gas reservoir identification.