油ガス田におけるAE法によるフラクチャー計測の可能性
2004 年 69 巻 6 号 p. 635-646
詳細
2004 年 69 巻 6 号 p. 635-646
A small-scale hydraulic injection experiment was conducted in the Yufutsu gas field in October 2003, to see the feasibility of AE (acoustic emission) monitoring for the purpose of the fractured reservoir delineation. Although many success stories have been reported from the area of geothermal fields, none of the study in oil/gas reservoir has been done in Japan. This is the first experiment in oil/gas reservoirs in this country. We have succeeded in recording more than 450 of good quality AE signals by downhole sensors installed at 2, 700-2, 790m depths during the injection of 280 tons of brine solution into the depth interval 4, 412-4, 995m in the gas saturated reservoir. As the results of AE analysis, it becomes clear that the distribution of the AE events has close relationship with the distribution of pre-existing fractures along the well and that the shearing associated with AE events improves the injectivity of the injection well.
The results of the field experiment were discussed through numerical simulations by using the "SHIFT" that simulates the shearing of fractures and relating permeability changes. The simulated results show a good matching in the pressure response and the AE activity, and provide us with useful understandings of the dynamics of the reservoir.
