Unconventional oil reservoirs, which are previously classified as uneconomic resources by traditional developing methods, have become one of the important world energy supplying parts in recent years with the application of horizontal drilling, hydraulic fracturing and numerous enhanced oil recovery (EOR) methods (K. Singh et al., 2019;Xie et al., 2021). These oil reservoirs usually bury deep underground with conditions characterized as high-pressure and high-temperature. In a typical unconventional oil reservoir exploitation, a hydraulic fracturing job is proceeded after the completion of horizontal drilling to increase transport channels for oil recovery (Z. Chen et al., 2020). Previously, a flowback operation of the fracturing fluid is usually designed to decrease the potential reservoir damage. However, recent developments in these oil fields showed that partly flowback or even no flowback with the subsequent shut-in operation increased the oil recovery (