Novel Models for Brittleness Evaluation in Unconventional Reservoirs

YUAN (Daniel) Hu


Rock is usually more brittle at low confining pressure and shows tendency toward ductility when the confining pressure increases, which is conflictive with the existing models in BI calculation. The effective stresses in the reservoir decrease at elevated pore pressure, which is equivalent to reducing the influence of confining pressure and thus increases the brittleness of rocks. The influence of temperature on rock texture at 0 confining pressure can be ignored. The relationship between temperature and pore pressure can be expressed based on thermoporoelastic equations. For brittle rocks, the larger the energy dissipaAon during the process, the smaller the fragments after rock failure. For plastic rocks, the energy consumption of plastic deformation should be considered. The new model matches well with experimental results, which consider the influence of Young’s modulus, Poisson’s ratio, tensile strength, confining pressure, pore pressure and fracture toughness in BI calculaAon and can be built by using conventional data like well logs or seismic data.