Marine riser-free subsea pump lifting drilling system circulation temperature change dynamic simulation method

The invention discloses a marine riser-free subsea pump lifting drilling system circulation temperature change dynamic simulation method. The method comprises the steps: obtaining operation parameters, environment parameters, well bore structure parameters and thermal parameters of a target well; respectively establishing a temperature control equation in the seawater section drill string, a temperature control equation in the stratum section drill string, a temperature control equation in the stratum section annulus and a temperature control equation in the seawater section return pipeline; determining initial and boundary conditions; carrying out discretization processing on the space structure of the whole system by adopting an internal node method; discretizing the control equation ona corresponding node; and finally, substituting the corresponding parameters into a discrete formula to calculate to obtain the circulation temperature in the seawater section drill string, the circulation temperature in the