AUTHOR=Yang Zhi-dong , Wang Yong , Zhang Xu-yang , Qin Ming , Su Shao-wen , Yao Zhen-hua , Liu Lingfu 

TITLE=Numerical Simulation of a Horizontal Well With Multi-Stage Oval Hydraulic Fractures in Tight Oil Reservoir Based on an Embedded Discrete Fracture Model

JOURNAL=Frontiers in Energy Research

VOLUME=Volume 8 - 2020

YEAR=2020

URL=https://www.frontiersin.org/journals/energy-research/articles/10.3389/fenrg.2020.601107

DOI=10.3389/fenrg.2020.601107

ISSN=2296-598X

ABSTRACT=Tight oil is a kind of unconventional oil and gas resources with great development potential. Due to the unconventional characteristics of low porosity and low permeability, in tight oil reservoirs, single wells generally have no natural productivity, and industrial development is usually conducted in combination with horizontal wells and hydraulic fracturing techniques. 
To capture the flow behavior effected by fractures with complex geometry and interaction, we adopted embedded fracture models (EDFMs) to simulate the development of fractured reservoirs. Compared with the traditional discrete fracture models (DFMs), the embedded discrete fracture models (EDFMs) can not only accurately represent the fracture geometry, but also do not generate a large number of refine grids around fractures and intersections of fractures, which shows the high computational efficiency. To be more consistent with real character of reservoir and reflect the advantage of EDFMs on modeling complex fractures, in this work, the hydraulic fractures are set as oval shape, and we adopted 3-dimenssion oil-gas two-phase model considering capillary forces and gravity effects. We developed an EDFM simulator, which is verified by using fine grid method (FGM). Finally, we simulated and studied the development of tight oil without and with random natural fractures. In our simulation, the pressure varies widely from the beginning to the end of the development. As real situation, tight oil reservoirs have high initial pressure and adopted step-down bottom hole pressure (BHP) development strategy where the BHP of last stage is below the bubble point pressure and the free gas will appear in the reservoir. Modeling studies indicate that the geometry of fracture has a great influence on the pressure and saturation profiles in the area near the fractures, dissolved gas flooding contributes to the development of tight oil, and natural fractures can significantly improve production, while the effect of stress sensitivity coefficient of natural fractures on production is more significant in the later stage of production with lower reservoir pressure.