Abstract:
Influenced by gas properties, reservoir lithology, reservoir physical properties and other factors, conventional logging methods are not efficient enough for both qualitative identification and quantitative evaluation of CO
2 gas. Taking the Enping depression as a case, based on the characteristics of hydrocarbon components in the oil layer, CO
2 gas layer and CO
2 oil layer, this paper, using the field gas logging data together with formation testing data and cable pumping sample data, creatively proposed some explanation charts for qualitative identification and quantitative evaluation of CO
2 based on the difference in hydrocarbon components in gas log. ① An effective qualitative identification chart is established for CO
2 gas reservoir, selecting C
1% and (C
3+C
4+C
5)/C
1 as the characteristic parameters of hydrocarbon components from gas log. ② A quantitative relationship between the CO
2 content and the C
1% of the reservoir is established with the data from gas log for quantitative calculation of the CO
2 content in the exploration stage. The method is applied for 3 fluorescence display layers in 2 exploration wells recently completed, and the interpretation coincidence rate reaches 100%. It has solved the problem of CO
2 qualitative identification and quantitative evaluation in the exploration stage, and also provided a strong technical support for the rapid decision-making of exploration and development operations.