Abstract: Refracturing is an important technique to tap the potential of reservoirs and boost production in depleted oil and gas fields. However, fracture propagation during refracturing, including both conventional refracturing and temporary-plugging refracturing remains poorly understood, especially for cases with non-uniform distribution of formation pressure due to long-term oil production and water injection. Therefore, taking pilot tests of refracturing with sidetracking horizontal wells in tight reservoirs in the Changqing Oilfield, China as an example, we establish a three-dimensional numerical model of conventional refracturing and a numerical model of temporary-plugging refracturing based on the discrete lattice method. Non-uniform distributions of formation pressure are imported in these models. We discuss the effects of key operating parameters such as injection rate, cluster spacing, and number of clusters on the propagation of multi-cluster fractures for conventional refracturing. For temporary-plugging refracturing, we examine the impacts of controlling factors such as the timing and number of temporary plugging on fracture propagation. In addition, we analyze a field case of temporary-plugging refracturing using well P3 in the Changqing Oilfield. The results show that fractures during refracturing tend to propagate preferentially and dominantly in the depleted areas. Improved stimulation effect can be obtained with an optimal injection rate and a critical cluster spacing. The proposed model of temporary-plugging refracturing can well describe the temporary plugging of dominant existing-fractures and the creation of new-fractures after fracturing fluid is forced to divert into other clusters from previous dominant clusters. Multiple temporary plugging can improve the balanced propagation of multi-cluster fractures and obtain the maximum fracture area. The established numerical model and research results provide theoretical guidance for the design and optimization of key operating parameters for refracturing, especially for temporary-plugging refracturing.