关键词: 连续损伤, 水平井, 射孔参数, 近井筒破裂形态, 数值模拟

Abstract: Perforation provides fluid conduit between wellbore and reservoir, hence it is an important controllable parameter for hydraulic fracturing stimulations. Focusing on the mechanism of fracture growth from perforation to near-wellbore in horizontal wells, a hydro-mechanical coupling model was used to analyze the stress change, together with continuum-based damage elements to characterize the three-dimensional fracture propagation and geometry evolution. A finite element program was developed to investigate the effects of perforation on fracture initiation pressure, failure location and near-wellbore fracturing complexity. The model was validated against the results of analytical model and perforation fracture experiments. The simulation results of horizontal well fracture initiation pressure were coincided well with the records of field test. The results indicate that: perforation can be used to control the fracturing pressure and propagation behavior of the initial fracture, which has a further effect on the fracture geometry of near-wellbore region in horizontal wells. Optimizing perforation parameters can lead initial fracture extend toward the preferred fracture plane. The results could help to decrease the fracture pressure, reduce the tortuosity and complexity of near-wellbore fracture caused by the helical perforations, and improve the fracturing stimulation effects of tight oil and gas reservoirs.

Key words: continuum damage, horizontal well, perforation parameters, near-wellbore fracture geometry, numerical simulation