Experimental Study on the Stress Sensitivity in Different Permeability Reservoirs

In order to study the stress sensitivity in different permeability reservoirs,the reservoir characteristics are considered,and the fractured cores with the matrix permeability of 18.876×10 ^-3μm²,234.247×10^-3 μm² and 540.12×10^-3 μm² are made by the Brazilian test.The permeability of these homogeneous cores and fractured cores are tested at different effective pressures.The influence of fracture on the reservoir stress sensitivity is studied by the characterization parameter of permeability retention ratio.The stress sensitivity in low permeability reservoir and high permeability reservoir is compared.The results show that the fractures can enlarge the stress sensitivity of reservoirs.The stress sensitivity of reservoir is influenced by the closure degree of fractures,and the stress sensitivity is strong in low effective pressures because the fracture is not compacted completely,while the stress sensitivity is weak after the effective pressures beyond to a limitation as the fracture is closed totally.With the increasing permeability,the stress sensitivity of fractured reservoir improves evidently while the stress sensitivity of homogeneous reservoir remains stable.From the actual reservoir properties,the fractures always develop in the low permeability reservoir and few exist in the high permeability reservoir,so the stress sensitivity in low permeability reservoir is stronger than that in high permeability reservoir.