Application of Quantitative Grain Fluorescence Analyzing Technology to Study of Tight Reservoir: A Case Study of Sha2 Member in Bozhong 27-2 Oilfield at Pitching End of Bonan Lower-uplift

The reservoirs at Sha2 Member of Bozhong 27-2 Oilfield is buried deeply (over 3 600 m) in Bonan lower-uplift of Huanghekou Depression, with very poor reservoir physical properties, which bring difficulty to interpretation of logging data and study of hydrocarbon accumulation. In order to identify reservoir hydrocarbon bearing conditions and restore the hydrocarbon filling history of Sha2 Member, a detailed study has been carried out with the technology of quantitative grain fluorescence analysis (QGF) and technology of quantitative grain fluorescence analysis of extracted fluid (QGF-E). The results show that QGF-Index and QGF-E of Sha2 member has obvious difference due to the difference in reservoir physical property. There is a palaeo-oil zone and a residual oil layer below the present oil-water contact. Combined with the analysis of hydrocarbon accumulation conditions, it is believed that hydrocarbon charging process of the tight reservoir of Sha2 member can be divided into three types, sufficient hydrocarbon charging type at hydrocarbon expulsion peak, not sufficient hydrocarbon charging type at hydrocarbon expulsion peak, and no charging type. The charging type at hydrocarbon bearing layer in B2 well belongs to early and late hydrocarbon charging type, while the dry layer from interpretation of logging data belongs to early hydrocarbon charging type or no charging type. The technique of quantitative grain fluorescence analysis can be used to identify hydrocarbon bearing layers in tight reservoir.