Kaiser效应点识别方法及储层地应力预测

Kaiser effect point identification method and in-situ stress prediction of

在储层岩心Kaiser实验中,声发射累积曲线通常出现多个突变点,导致常规Kaiser效应点识别方法不精确,甚至存在无法读取Kaiser点的问题。为此,提出将声发射能量图谱与声发射累积曲线结合的Kaiser效应点优化识别方法,并用于某油田X区块储层地应力预测。岩心单轴加载实验结果表明:加载初期,岩心处于压缩阶段,声发射数量较多,声发射能量值波动范围较大;加载中期,岩心处于弹性形变阶段,声发射数量较少,声发射能量值较低,变化幅度均一;加载后期,应力达到储层岩心破裂压力,岩心发生破裂,声发射数量急剧增加,声发射能量值达到峰值。加载中期阶段,当轴向应力达到储层岩心承受的历史最大应力时,岩心突然释放大量能量,声发射数量和能量值均突增,随后迅速降低,该现象与Kaiser现象相吻合,因此通过声发射能量图谱与声发射累积曲线结合的方法能够识别Kaiser效应点。利用优化后的Kaiser效应点识别方法,分析某油田X区块地应力分布,计算结果与现场测试结果吻合。

There are multiple mutation points in the acoustic emission(AE)cumulative curve in the Kaiser experiments of reservoir cores,causing the routine Kaiser effect point discriminant method to be inaccurate,and there is even a problem that the Kaiser point cannot be read.To solve this problem,an optimized Kaiser effect point discriminant method combining AE energy spectrum and cumulative AE curve is proposed in this paper and applied to the prediction of reservoir in-situ stress in Block X of an Oilfield.The experimental results of core uniaxial loading show that at the initial period of core loading,the core is in the compression stage,with a large number of AE and a wide fluctuation range of AE energy values.In the middle period of loading,the core is in the elastic deformation stage.The amount of AE is small,and the AE energy value is low.The range of change is uniform.At the late loading period,the stress reaches the fracture pressure of the reservoir core,and the core ruptures.The number of AE increases sharply,and the AE energy value reaches a peak.In the middle period of loading,the core suddenly releases a large amount of energy,and the AE number and energy value have a sudden increase,followed by a rapid decrease when the axial stress reaches the historical maximum stress of the reservoir core.This phenomenon is in accordance with that of Kaiser.Therefore,the Kaiser effect point can be determined by combining the AE energy spectrum and cumulative AE curve.By using the optimized Kaiser effect point discriminant method,the in-situ stress distribution in Block X of an Oilfield is analyzed,and the results are in good agreement with the field test results.