Calculating single layer production contribution of heavy oil commingled wells by analysis of aromatic parameters in whole-oil GC-MS

Abstract

Traditional fluid production profile logging is not usually suitable for heavy-viscous crude oil wells. Biodegradation of heavy oil can lead to the loss of n-ahkanes, and the use of chromatogram fingerprint techniques in studying the production contributions of single layers in heavy oil commingled wells has limitations. However, aromatic compounds are relatively well preserved. We took the heavy oil commingled wells of small layers NG55 and NG61 in the ninth area of the Gudong oil field as examples. Based on the principle of chromatography, the whole-oil GC-MS was used, and the aromatic parameters which have a strongly linear relationship with the ratio of mixed two end member oils were verified and selected in laboratory. Studies showed that the ratio of (1, 4, 6- + 2, 3, 6-trimethylnaphthalene) to 1, 2, 5-trimethylnaphthalene has a strongly linear relationship with the ratio of the mixed two end member oils (R2=0.992). The oil contributions from single layers NG55 and NG61 in six commingled heavy oil wells were calculated using established charts and this relationship. The calculated results are consistent with the results of long period dynamic monitoring and logging interpretation in the study area and can provide a scientific basis for monitoring production performance and hierarchical management of reservoirs. The study provides a new geochemical method for calculation of the contributions of single layers in heavy oil commingled wells when conventional fluid production profile logging is not suitable.