Discrete element method simulation of the growth and efficiency of multiple hydraulic fractures simultaneously-induced from two horizontal wells

Multiple hydraulic fracturing treatment from horizontal wells has been widely used to enhance the productivity of unconventional hydrocarbons. Interaction among the fractures can cause the reorientation of fractures and lower the stimulation efficiency. We perform discrete element method (DEM) simulations to assess the influence of completion scheme on the trajectory and efficiency of fractures simultaneously-induced from two horizontal wells. Simulation of a single hydraulic fracture yields reasonable agreement with the theoretical solution regarding the fracture pattern and stress alteration and thus confirms the validity of the model. Stress shadowing effect caused by the opening of early fractures alters the state of local stress and thus leads to the appearance of dominant fractures and the reorientation of other fractures located in the altered stress field. Influences of the fracturing scheme including the distance between wells, the spacing between injection points, and arrangement of injection points are examined. The distribution uniformity index reveals that the effect of distance between wells on improving the efficiency of treatment is conditionally dependent on the spacing between injection points. Under the conditions considered in this study, the distance between wells enhance the efficiency only when the spacing reaches 40 m. Similarly, enlarging the spacing between injection points does not affect the distribution uniformity index when the distance between wells is 40 m, but effectively mitigate the stress shadowing effect and promotes the fracturing efficiency when the distance exceeds 60 m. Arrangement of injection point plays a negligible role on the fracturing efficiency compared with the spacing among them.