Simulator of Pressure Loss in Circulative System During Drilling or Cementing ﷯ The simulator allows to calculate pressure losses in borehole during drilling and cementing. Approximation of rheological characteristic measured by a viscosimeter with two-power and polynomial model of non-Newtonian liquid, provides best precision among similar methods of pressure computation, because the polynomial model in computations uses full information received from multivelocity viscosimeters. Z-criterion, usually used for a non-Neutonian liquid power model is used in the simulator for determining the flow type. The borehole circulating system channel consists of tube sections of round and annular profile with a constant area, during calculations their flow type is determined. Then simulator computes pressure losses for two-power and polynomial models of liquid flow. Precision benefits from using polynomial model are most significant for high viscosity muds with complicated rheology.