Given the abundant reserves, shale oil resource has great potential for future utilization. However, shale formation is often characterized by complex geological structures and developed stratification, which greatly restricts the formation stimulation performance of volumetric fracturing along the vertical direction in horizontal well and therefore raises development costs. To address such issues, a new method that utilizes radial-borehole fracturing based on vertical well is proposed to extract shale oil. This paper describes the fracturing network under radial borehole fracturing. A numerical model that considers shale formation, hydraulic fractures, and the wellbore is built to predict the productivity of radial-borehole fracturing and horizontal well fracturing. Moreover, a simplified cost evaluation model is built, respectively.

Furthermore, this paper analyzes the influence of different well patterns, fracture heights, and Kv/Kh ratios on radial-borehole well productivity and compares the cost-effectiveness of a radial-borehole fractured well and horizontal well fracturing. Results indicate that radial-borehole fracturing is capable of eliminating the constraints of fracture height and thereby improving stimulation performance; more radial boreholes and main wells result in more oil production; in addition, as the fracture height decreases, the ratio Kv/Kh is closer to 0, it is more recommended to use radial borehole fracturing. A case study of Eagleford shale oil reservoir is herein carried out: The 9-vertical well, 3-layer, 4-lateral radial borehole fracturing brings the same oil production as the 3-horizontal well multistage fracturing (open hole completed) does, while the former costs 0.36 M$ less of the latter. Using radial borehole fracturing method to develop shale oil is proposed in this paper. The results can provide new insight into the effective development of shale oil resources at low cost.

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