Abstract: During heavy oil catalytic aquathermolysis assisted by steam huff and puff, chemical properties of crude oil within these formations may vary to some degree due to temperature distribution differences. To appropriately simulate such changes of crude oil in these formations and predict well productivity with steam-assisted huff-and-puff in heavy oil development, the impact of distribution of temperature fields within the formation on heavy oil catalytic aquathermolysis are expressed in terms of viscosity change versus temperature. In the simulation, only the two-phase flow of oil and water are considered while gravity and capillary forces are not taken into account.Then those changes are introduced into the well-developed model in numerical simulation of steam-assisted huff-and-puff operations to construct numerical model for 2D two-phase steam-assisted huff-and-puff operations. In addition, techniques available to obtain relevant solutions are also provided. The model was used to simulate field tests of the fourth round of steam-assisted huff-and-puff catalytic aquathermolysis in Well K92N6 in the Gudong Oilfield. According to calculation results, oil production in this round of development would be around 4 560.4 t, while the actual production during the period was determined to be 4 899.7 t. The difference between actual and simulated was reasonable, about 6.92%, which could meet engineering requirements. Research results demonstrated that crude oil for catalytic cracking can be classified into three categories: unreacted, low-temperature reactive and high-temperature reactive according to temperature distribution around the borehole during steam-assisted huff-and-puff. The viscosity-temperature relationships of crude oil after cracking and modification of the three types can be placedinto theexponential function of temperatures and then be introduced into a mature steam-assisted huff-and-puff model to perform mathematically approximate characterization and simulation of the irreversible property changing progress in catalytic cracking during steam-assisted huff-and-puff processes. Relevant simulation results will provide guidance in optimization of technical parameters and inthe prediction of productivity for catalytic cracking techniques in steam-assisted huff-and-puff operations.