濮城油田注水驱油引起的地震活动特征分析

Characteristics of the seismic activity associated with fluid injection in Pucheng oilfield

利用孔隙压力扩散机制,分析了濮城油田注水引起的地震活动特征,获得了油田开发期不同时段的流体孔隙压力扩散特征,并分析了注水压力、注水量与诱发地震的频度、震级之间的相关性特征.研究结果表明:濮城油田与注水有关的地震活动表现出明显的分期特征,基于孔隙压力扩散过程触发机理,计算出孔隙压扩散系数在初期注水量增加时段(1980—1994年)约为0.1 m^2/s,在注水量保持稳定时段(1994—2006年)在0.12~0.16 m^2/s之间,在实施层间精细注采措施后(2007年后)约为0.05 m^2/s;濮城油田注水诱发地震的地震频度、最大震级和注水压力、累积失水量之间存在一定的相关性,其地震年频度和注水压力、累积失水量之间呈现指数相关特征,其最大震级和注水压力、累积失水量之间呈现线性相关特征.本项研究对分析解释注水诱发地震机理、定量评价注水诱发地震的危险性具有一定的参考价值.

Using the mechanism of pore pressure diffusion,we analyzed the characteristics of seismic activity associated with fluid injection and the fluid pore pressure diffusion at different times during the development period of Pucheng oilfield. We also analyzed the relationships between the water injection pressure,injection water volume and the frequency,magnitude of induced earthquakes. The results shows as following： the seismic activity associated water injection in Pucheng oilfield showed significant stage characteristics, we calculated the pore pressure diffusion coefficient based on the trigger mechanism of pore pressure diffusion process,and the results shows that the pore pressure diffusion coefficient increased in the initial injection period（ 1980—1994）and is about 0. 1 m^2/s,between 0. 12 to 0. 16 m^2/s in the period（ 1994—2006） while injection volume unaltered,and is about 0. 05 m^2/s after using the interlayer fine injection-production measures;Seismic frequency, maximum magnitude of those earthquakes induced water injection related to the injection pressure and accumulated water loss. There is an exponential relationship between the earthquake frequency and the water injection pressure,accumulated water loss, and linear correlation between the maximum magnitude and the water injection pressure,accumulated water loss. This research may be helpful to the study of the mechanism of earthquake induced water injection, and to quantitatively assess the risk of water injection.