The invention relates to a method for determining reservoir
porosity based on PDC
rock breaking simulation and
logging mechanical
specific energy. The method comprises the following steps: constructing a
dynamic modulus and first static modulus state conversion model; combining the
dynamic modulus and first static modulus conversion model with the
porosity and
dynamic modulus relationship to construct a
porosity and first static modulus model; a stratum model is constructed, and a second static modulus is set according to the range of 10-80 GPa; creating a PDC
drill bit model, and fixing a reference point; surface-surface contact is adopted, a
drill bit-stratum
action model is set, and an eight-node reduction integral unit is adopted for grid division;
rock breaking simulation is carried out, and the drilling pressure, the rotating speed, the torque and the mechanical drilling speed under different second static moduli are extracted. Calculating a mechanical
specific energy value by using the drilling pressure, the rotating speed, the torque and the mechanical drilling speed; regression fitting is carried out on the obtained mechanical
specific energy value in an index form, and a mechanical specific energy and second static modulus relation model is constructed; enabling the first static modulus to be equal to the second static modulus, and constructing a porosity and mechanical specific energy relation model; and collecting and filtering the while-
drilling engineering parameters, substituting the while-
drilling engineering parameters into the porosity and mechanical specific energy relation model, and determining the porosity value of the reservoir in real time. The method has the advantages of low cost and
continuous data points, and the porosity can be quantitatively monitored in real time in the while-drilling process.