Preparation and evaluation on artificial core of extra high permeability unconsolidated sandstone

Unconsolidated sandstone is characterized by low consolidation degree, loose structure and low strength. And besides, its coring cost is high and the cores cannot be shaped easily. As a result, the cores are not applicable to laboratory experiments. In this paper, it was proposed to make unconsolidated cores of extra high permeability to replace some reservoir cores. To evaluate the reliability and representativeness of artifcial cores, the rock samples were investigated from the aspects of size composition, mineral composition, porosity, permeability, consolidation mode, consolidation index, pore structure, compressibility coeffcient, mechanical property and percolation characteristic. It is indicated that the lower the pressing pressure and cement content are and the higher the water fooding strength is, the lower the rock strength is, the looser the rock is and the more easily it can be damaged. The yield stress decreases exponentially with the decreasing of pressing pressure, and logarithmically with the decreasing of cement content and the increasing of water fooding strength. To prepare extra high permeability unconsolidated cores with certain strength, the pressing pressure shall be at least 4 MPa and the cement content shall be about 5%. It is demonstrated that the artifcial unconsolidated core is similar with reservoir cores all around, and it can replace the reservoir core for experiments. It can be used as the reference for the investigation of ultra high permeability unconsolidated cores.