Multiple stage fracturing with multiple pads (MSFMP) is an essential technology for efficient development of unconventional reservoirs, but connecting area of two well pads is still not stimulated. The in-situ stress in the connecting area of well pads would be disturbed after MSFMP, affecting the initiation and near-wellbore propagation of infill horizontal well whose horizontal wellbore deviates greatly from the optimal orientation. Therefore, this paper proposes a method for calculating the stress perturbation caused by MSFMP and then optimizing the perforation parameters of infill horizontal wells in the unstimulated area. The results show that stress disturbance at any position can be calculated based on the stress disturbance model, and then the optimal fracturing interval is obtained in the middle unstimulated area. Appropriate perforation parameters can significantly decrease the complexity of near-wellbore fractures.
The stress shadow (or induced stress) generated due to the formation of hundreds of hydraulic fractures during multiple stage fracturing with multi-well pads (MSFMP), leading to redistribution of the in-situ stress and affecting the propagation of subsequent fractures. To further maximize the recovery, infill horizontal wells whose horizontal wellbore azimuth deviates from the optimal wellbore azimuth (the minimum in-situ stress direction) need to be arranged in the middle unstimulated area (Figure. 1). However, the redistribution of in-situ stresses in the middle unstimulated area is complex after MSFMP of multiple layers.
Many significant efforts have been made on the calculation of stress shadow and its influence on fracture propagation [1–5]. The present stress calculation, however, mainly focuses on the stress shadow caused by single or multiple hydraulic fractures in the same layer, and the influence of stress shadow on fracture initiation and propagation of adjacent fracturing stages or wells is mainly concerned. It is rare to find that stress shadow after MSFMP of multiple layers, especially in the unstimulated connection area of well pads, is calculated. Therefore, it is urgent to establish a quick calculation method of complex stress shadow for MSFMP of multiple layers.
