Abstract:

 The beachbar sand bodies in the upper fourth member of the Eocene Shahejie Formation(the upper Es4) in Dongying Depression exhibit zonal distribution in a plane. The secondary pore developed in beachbar sand bodies in the study area is an important factor to form favorable reservoir. The secondary pores can be mainly divided into carbonate dissolution pores and quartz dissolution pores, which were respectively formed in two different fluid environments. Based on the study of the secondary pore and the diagenesis in different beachbar sedimentary areas, it is considered that the genetic types of the secondary pore vary in different structural locations in Dongying Depression, as the solid and fluid properties are highly different in the reservoir of beachbar sand bodies. The differences of solid properties are caused by the distance from the sedimentary body to the provenance and the variation of sedimentary environments, while the differences of fluid properties result from the connectivity and activity of faults near the sedimentary body. Therefore, the secondary pore of beachbar sand bodies shows corresponding zonal distribution laterally: the secondary pore zone developed in the gravel beachbar was mainly controlled by acid diagenesis; the secondary pore zone existed in the coastal beachbar was affected by interaction of acid and alkaline diagenesis; and the secondary pores in the offshore and the central resonance zone beachbar reservoir were mainly affected by alkaline diagenesis.

Key words: Dongying Depression, beachbar, secondary pore, genetic mechanism, distribution model