HOW TO ELIMINATE THE DEFECTS OF GCF APPLIED TO THE PRODUCTION-PARTITIONING CALCULATION OF CRUDE OIL IN CONPRODUCING WELLS

As an important technique in the reservoir geochemical domain,the gas chromatographic fingerprints technique (GCF) has made great contribution to the administration and development of oilfields.GCF has won initial success when applied to the production-partitioning calculation of crude oil in conproducing wells.But many defects as follows were revealed during its application.(1) As GCF is affected by noise unavoidably,the requirements for the stability of instruments are very strict.(2) the amount and velocity of inlet samples must be kept identical on the whole.(3) The determination of peaks is relatively difficult for biodegraded oil without n alkane.(4) The peak height is greatly affected by the integration method the operator selects.(5) As the "standard plate" method established on the basis of absolute linear stacking has not strict universality,the approximation has defects theoretically and correct results cannot be obtained usually by means of conventional mathematical methods.(6) The questions about trilayer conproduction have not been resolved better.About its theoretical defects,it is proved by strict mathematical deduction that there is no linear stacking relationship between peak height ratios and production-partitioning percentages.Furthermore,the internal standard method and the bias least square method two improving schemes aimed at the above defects were suggested,and the later scheme was studied and discussed emphatically and thoroughly.By improvement on original GCF,the absolute error between predicted and measured values for artificial partition mixed oil is less than 5%. This proved the accuracy and reliability of the later scheme.The comparison of the calculation results from the later scheme with those from the ultraviolet spectral technique (UV) for the same conproducing well shows that the two methods have quite good coincidence and comparability.At last,the respective appliable ranges of GCF and UV two techniques are discussed in detail.As the two techniques are mutually complementary,we must make selections according to concrete conditions in the course of application.