关键词: 特低渗透油藏, 水力压裂, 定向射孔, 转向压裂, 双S型裂缝, 计算模型

Abstract: In order to improve fractures in new wells of low-permeability reservoirs,a new methodology to generate dual-S fractures in deflection fracturing of oriented perforation was proposed.The three-dimensional finite element method was used to study the mechanism of fracture initiation in oriented perforation.Considering the shape of arbitrary fracture,underground stress and fluid pressure distributed in fractures,a model for specifying stress intensity factor of arbitrary fracture was set up.The propagation criteria for mixed-type fracture of type Ⅰ and type Ⅱ were also presented.The models and computation procedures for determining fracture propagation path were provided,and the software for simulation of fracture propagation was developed.Surface micro-seismic technique was used in fracturing treatment of three wells to monitor fracture propagation directions.The monitoring results agreed well with the model prediction.The dual-S type fractures can be generated in a single formation by using oriented perforation fracturing technology,which may be an effective method to improve oil production in ultra-low permeability reservoir.

Key words: ultra-low permeability reservoir, hydraulic fracturing, oriented perforation, deflection fracturing, dual-S fracture, computation model