Abstract:

A total of 250 sandstone samples were selected from various sections of the Paleogene(dominated by the Shahejie Formation) in the Dongying Sag of the Bohai Bay Basin to measure their compressional-and shear-wave velocities by pulse transmission techniques under simulated reservoir conditions.Statistic petrophysical models under reservoir conditions,such as velocity versus porosity and velocity versus density,were built based on the measured data.On the cross plot of P-wave velocity vs.Possion's ratio,the samples show two major trends,which reflect the effects of shale content and calcareous cement content on the elastic properties of sandstone samples respectively.For each trend,the rock texture changes gradually from grain-supporting to matrix-supporting with the increase of shale content and calcareous cement content,and thus the propagation of elastic wave also changes from via grain-to-grain contacts to via rock matrix.These are the main reasons for the two entirely different trends of the sandstone samples.The results provide a basis for extracting information about rock texture,sedimentary and diagenetic features by using the petrophysical properties of reservoir sandstones.

Key words: seismic elastic attributees, rock texture, sandstone reservoir, Paleogene, Dongying Sag, Bohai Bay Basin