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中深层砂砾岩体叠前地震成像技术应用研究

The Applied Research of Seismic Pre-stack Imaging Technique on Medium-deep Glutenite Body

【作者】 吴常玉

【导师】 杜世通;

【作者基本信息】 中国石油大学 , 地质资源与地质工程, 2009, 博士

【摘要】 胜利油田在砂砾岩体储层多口探井的钻探及试油相继获得重大突破后,显示出济阳坳陷陡坡带砂砾岩扇体油气藏巨大的勘探潜力,从早期对砂砾岩体沉积特征的认识――单断式边界断裂控制的砂砾岩体受坡度的影响在横向展布范围上较窄,向湖一侧不易发育砾岩体――转变为新的认识和理论:构造活动强度大,物源充足,纵向上厚度较大,极易发育三角洲前缘滑塌的砂砾岩体,储集空间得到有效改善,物性变好易成藏。波动方程有限差分正演模拟方法揭示了中深层砂砾岩体的地震反射特征。主要表现为内部反射杂乱且变化,顶底及前缘上有较强的连续或断续反射;频率较低也有变化,频率的成层性较差;盐下堆积的砂砾岩体大多表现为块状杂乱弱振反射,其间较为连续的反射与不同期次的沉积砂体有关。高阶广义屏叠前深度偏移方法基于反问题求解中常用的摄动理论,根据速度场的非均匀程度自动在空间与波数域交替进行波场延拓。它兼具傅立叶变换方法、有限差分方法各自的优点,可以自适应于介质的复杂性。双域操作的方法大大降低了数值离散所造成的格点频散,并且计算量较时间-空间域中有限差分偏移技术小,从而使之对横向变速的适应能力有了显著提高。针对中深层砂砾岩体区从地质及地震资料方面的分析、具有代表性过井剖面的正演模拟的基础上,开展有针对性的保幅处理方法、一致性处理方法及数据规则化方法研究;同时,开展实际地震资料处理应用工作,进一步提高了中深层砂砾岩体的成像精度及分辨能力,满足济阳坳陷陡坡带砂砾岩体油藏描述的需要。

【Abstract】 Since 2005, many exploration wells such as Che66, Fengshen1, Yan22, Lishen1 and etc. in Shengli Oil Field have made major breakthrough in drilling and production test, which shows that the fan-shaped glutenite reservoir near the abrupt slope area in Jiyang Depression has great exploration potential. Early understanding of the glutenite depositional features were as follows: The glutenite body controlled by single boundary faulting became narrow in the lateral distribution due to the impact of the slope, and the conglomerate body was difficult to develop to the lake side, resulting in relatively low degree of prospecting. Now we have new understanding of the glutenite depositional features: With strong structural activities, adequate sources and bigger vertical thickness, the glutenite body was easy to be developed from the delta front slump. The reservoir space has been effectively improved, and the better physical properties make it easy to form a reservoir.Through forward modeling technique, we understood the seismic reflection characteristics of the medium-deep Glutenite body as follows: the internal reflection was disorderly and constantly changing, strong continuous or discontinuous reflection occurred on the top, the end and the front of Glutenite Body; The frequency is low and can be changeable with bad frequency stratification; Most of the glutenite accumulated under salt dome showed the reflection features of massive size, weak amplitude. Some of the continuous reflection is related to the depositional sand body from different times.In this paper, a dual-domain wave equation pre-stack depth migration method for solving inverse problems is based on commonly used perturbation theory. By using of this method, the wave field alternatively extends between space and wave number domain automatically in term of the non-uniformity of velocity field. This method combines Fourier transform method and finite difference method with their respective advantages, and can be adaptive to the complexity of medium. Wave travels freely in the wave number domain through a uniform medium with some sort of reference velocity. The reference velocity can change with depth with maximum angle up to90 o.The interaction between wave and the non-uniform medium in the space domain is carried out by modifying wave front. The method using dual-domain can greatly reduce the grid dispersion caused by numerical dispersion, and the calculation work in time - space domain is less compared with the finite difference migration technique. This method will significantly increase the adaptability to lateral velocity variation.In this paper, geologic and seismic data analysis especially for glutenite rock in the medium-deep zone has been conducted, and typical through-well cross sections have been selected for forward modeling. Based on this, specific processing study work has been carried out. Meanwhile, 3D seismic data processing technique has been used in around Fengshen1 well area. The application of the technique has further enhanced the imaging precision and resolution of the glutenite body in the medium-deep, and met the need of the glutenite reservoir description near the abrupt slope area in JiYang Depression.

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