Refracture technique has been a common practice to mitigate the flow rate decline and revitalize wells productivity. However, refracturing design in tight resource wells is difficult because the dynamic stress changes due to long term reservoir depletion. This paper presents a workflow for the refracturing in tight oil reservoirs with the geological modelling, geomechanical modeling and refracturing fracture simulation. The combination of the core, logging, and seismic data were used to establish the reservoir, natural fracture, rock mechanical, and in-situ stress models. Moreover, the perforations in the refracturing stage were also selected with three main factors, including the remaining oil distribution, low formation pressure and average production index per pressure decline rate. Thus, dense cluster spacing fracturing and temporary plugging methods can be applied to create new and old fractures depends on the updated reservoir properties. Using a loose coupled technique, the in-situ stress prior to refracturing was computed and local dynamic stress change can be found along the horizontal well lateral stage. Numerical simulations indicate fluid injection volume and pump rate have critical influences on the reservoir stimulated volume (SRV) while the best scenarios can be determined for the given case. Compared with the initial fracturing, the SRV volume of the refracturing is increased by 150%, which is beneficial for oil production increase in this area. The field application demonstrates that refracturing can greatly improve well production in the tight oil reservoir.
Due to complex lithology, strong heterogeneity, and low permeability in tight oil reservoirs, the oil production in many reservoirs is not ideal. Thus, refracturing techniques have been regarded as one important oil recovery technique. The continuous development of reservoirs makes residual oil-rich and low-pressure areas near production wells increasingly evident. The long-term production of hydraulic fractured wells can lead to the depletion of the formation pressure, possibly reducing their production capability. To mitigate the rapid decline in oil production, refracturing treatments are introduced to enhance recovery and increase production. Previously, refracturing optimization design was primarily focused on a vertical well, and conventional design ideas were used to determine the timing of fracture reorientation. However, the optimization design for refracturing in horizontal wells is more complex. Significant variations in formation pressure, geomechanical properties, and in-situ stress occur along the lateral stage of horizontal wells due to the long-term depletion and previous stimulated volume. Thus, it is necessary to consider the significant impact of geomechanical properties and in-situ stress change on fracture propagation during refracturing treatment.
