塔河地区面向缝洞体的地震采集优化策略研究

Research on optimization strategy of seismic acquisition for fractured-cavity bodies in Tahe area

塔河油田随着开发的深入,高精度三维地震资料已经不能完全满足需求,面临着小尺度缝洞预测难、规模缝洞体结构、连通关系及剩余油描述难等问题。这里从塔河地区现阶段地震开发面临的问题出发,结合塔河地区地震地质条件、高精度三维采集方法与应用效果和影响缝洞体成像的地震采集关键因素分析,研究了面向小尺度缝洞的地震采集优化策略。证实了影响塔河地区小尺度缝洞体成像最重要的因素是地震资料的信噪比,而提高信噪比最有效的手段是增加覆盖次数;其次要做好缝洞绕射的记录与保护,减小采集面元更充分地记录好绕射波场,减小检波器组合更好地保护好绕射波场,为绕射波成像提供数据基础。提高缝洞体结构以及连通关系的描述精度,需要进一步拓展地震资料的有效频带;塔河地区地震激发接收条件好,具备一定的拓展频带的空间;一方面采用低频检波器接收更好的记录低频信息,在压噪处理时保护低频信息,拓展有效低频,提高地震资料倍频程;另一方面通过高叠次进一步压制高频随机噪声,突出有效反射,拓展有效高频。采用以上优化策略在塔河地区开展了地震采集试验,小尺度缝洞体的成像精度明显提高。

With the in-depth development of Tahe Oilfield,high-precision 3D seismic data can no longer fully meet the needs,and it faces problems such as difficulty in predicting small-scale fractured cavities and difficulty in describing the structure,connectivity,and remaining oil of large-scale fracture-cave bodies.In this paper,the optimization strategy of seismic acquisition for small-scale fractured cavities is studied by starting from the problems faced by the current seismic development in the Tahe area,and combining with the seismic geological conditions in the Tahe area,the high-precision 3D acquisition method and application effect,and the analysis of the critical factors of seismic acquisition that affect the imaging of fractured-cavity bodies.It is believed that the most crucial factor affecting the imaging of small-scale fracture-cave bodies in the Tahe area is the signal-to-noise ratio of seismic data.Therefore,the most effective means to improve the signal-to-noise ratio is to increase the coverage times.Secondly,to provide the data basis for diffraction wave imaging,it is necessary to record and protect the diffraction of the fractured cavities,reduce the acquisition bin to record the diffraction wave field more fully,and reduce the geophone combination to protect the diffraction wave field better.To improve the description accuracy of fracture-cavity structure and connectivity,further expanding the influential frequency band of seismic data is necessary.There is a particular space for expanding the frequency band because the seismic excitation and reception conditions are good in the Tahe area.On the one hand,low-frequency geophones are used to record low-frequency information better and protect low-frequency information during noise suppression to expand effective low-frequency and improve the octave of seismic data.On the other hand,high stacking times further suppress the high-frequency random noise to highlight the adequate reflection and expand the effective high frequency.Using the above optimization strategy,a seismic acquisition experiment was carried out in the Tahe area,and the imaging accuracy of small-scale fracture-cave bodies was significantly improved.