The Analysis Of Mechanical Parameters In Unconsolidated Sandstone

Unconsolidated sandstone is one of the most common reservoir rocks,which prevails both domestic and overseas.During unconsolidated sandstone reservoirs exploitation,reliable physical and mechanical properties are obtained.Due to unconsolidated sandstone of high porosity,high permeability and weak cementing strength,pore pressure and temperature affecting unconsolidated sandstone mechanical properties should be considered.From the triaxial test and thermo-solid coupling analysis,the main conclusions were as follows:(1)With the increase of pore pressure,compressive strength of unconsolidated sandstone came down.Elastic modulus dropped largely at low pore pressure,meanwhile elastic modulus dropped small at high pore pressure.Poisson's ratio increased firstly and decrease subsequently.(2)Elastic modulus and compressive strength were well fitted with quadratic fitting precision of pore pressure.The Poisson's ratio was poor quadratic fitting precision with pore pressure.So Poisson's ratio did not have the exact correlation with pore pressure.(3)With the increase of temperature,unconsolidated sandstone compressive strength increased firstly and decreased afterwards.The compressive strength decreased sharply until temperature got the limited value,which was opposite to the rock stability.(4)Though numerical simulation of the compressive test under different pore pressure and temperature,equivalent plastic strain was similar to the result of experiment.According to the mechanical parameters,temperature influence on wellbore and sandstone was investigated with ABAQUS simulating the process of themo-dynamic oil exploitation.From the result of simulation,the temperature influence of well stability should be considered in unconsolidated sandstone.