Abstract: Abstract:Study of four well cores and relevant data of other wells obtained from the Upper Permian Changxing Formation in the Huanglongchang structure has demonstrated that there are organic reefs in cores from the Huanglong No. 1 well and Huanglong No. 4 well but no reefs in cores from the Huanglong No. 3 well and Huanglong No. 5 well. The reefs consist of sponge bafflestones, wh ICH belong to carbonate platform margin reefs. Due to little difference in physical properties of reef and strata strong heterogeneity Nonreef, in reefs and outstanding multiple solutions to the prediction problem, the authors used the prediction method of combining geological, logging and seismic approaches to determine the boundary of the organic reef gas reservoir in the Huanglong No.1 well area and found an organic reef gas reservoir on the western side of the Huanglong No. 5 well. Thus a practical method for predicting reefs is provided.