Horizontal well volumetric fracturing technology is typically used to increase oil and gas production from a single well and the ultimate recovery rate of a reservoir by creating a network of artificial fractures and increasing the effective reservoir seepage volume. Nevertheless, the constraints imposed by the limited extent of the fracture network and the subsequent partial closure of fractures at subsequent stages can result in complications such as a rapid decrease in production and a low primary recovery rate of horizontal wells. To provide a foundation for subsequent fracturing and modification programs, clarifying the residual oil saturation in each fracturing section is critical. This paper proposes a novel methodology for calculating residual oil saturation in volumetric fracturing sections of horizontal wells, with tight conglomerate reservoirs in the Mahu Sag of the Xinjiang Oilfield as an example, and establishes a quantitative calculation model for residual oil saturation across different fracturing sections. First, an equivalent cuboid-like model for fracture-controlled reserves in various fracturing sections was developed on the basis of the control range of fracture network spreading characteristics and their effect on the effective utilization of crude oil within pores and throats, resulting in the establishment of division coefficients for oil production across these sections. Second, the total oil production of a well was divided among different fracturing sections to obtain the remaining fracture-controlled reserves within each fracturing section. Last, a quantitative calculation model for fracture occurrence was established via the multiple linear regression method. This model can be used to accurately predict fracture parameters for horizontal wells without microseismic monitoring. The above method was employed to determine the residual oil saturation in different fracturing sections, which can effectively guide research on the planar distribution of residual oil in tight conglomerate reservoirs in the Mahu Sag. The theoretical model of this method can be applied to different types of tight reservoirs. To accurately calculate the residual oil saturation in different fracturing sections, the corresponding model parameters for specific reservoir types must be determined. This method has broad market application prospects.
Jing et al. (Sun,) studied this question.