摘要
在东部平原地区,由于地表地质条件变化不大,原始地震数据中有效反射波相对稳定,静校正问题及各类干扰不十分突出,信噪比相对较高,在常规处理中已形成了一套相对稳定的地震数据处理流程。
复杂地表低信噪比地区地震资料,由于地表及地下地质条件复杂,激发及接收条件差,在原始采集记录上存在着严重的静校正问题及各类强干扰,记录上几乎看不到有效反射波的影子,原始资料信噪比低,静校正问题突出。用常规的地震数据处理流程根本无法满足地质任务的需要,严重影响着此类地区油气勘探与开发的进程。
塔里木盆地沙漠地区地表起伏大,低降速带和表层速度横向变化剧烈,静校正问题十分突出;另一方面,受巨大沙丘的影响,采集的地震数据中侧面干扰十分严重,导致地震记录信噪比较低,有效信号淹没在强能量侧面干扰、散射干扰之中,在采集到的有些原始单炮记录上很难看到有效反射波的影子。
本文针对该区地震数据的特点,着重从静校正和叠前去噪入手,以解决因沙丘起伏产生的静校正问题并压制各种噪声干扰,从而提高资料的信噪比。
在解决该区静校正问题方面,采用了配套的静校正技术。首先,总结了新的沙丘曲线公式,以解决长波长和中波长静校正问题;采用交互折射静校正技术,以解决大的剩余静校正问题;采用分炮检距地表一致性剩余静校正的方法,以解决同一共反射道集中不同炮检距的剩余静校正差异问题。
在叠前去噪方面,采用中值滤波、自适应低频噪声压制、强能量干扰波压制等技术,对不同的噪声分别压制。同时,根据噪声在不同“域”存在的线性关系和强弱关系不同,采用“多域串联”去噪的方法,取得了较好的处理效果。
In the eastern plain of China, the surface geological conditions vary mildly, so the reflections in raw seismic data are relatively stable, the problems of static correction and all kinds of disturbance are not much severe and the Signal-to-Noise Ratio (SNR) is relatively high. A set of methods in seismic data processing have been established in the routine processing.
However, for the seismic data from the low SNR region with complex surface, because of the complicated surface and underground geology structures and the poor transmitting/receiving conditions, there exist severe static correction problem and strong disturbance in the original records so that reflections can not be identified in raw data. The needs of geological task cannot be met with the routine seismic processing methods, which influences badly exploring and developing in this kind of areas.
In the desert region of talimu, the surface is very complex. The strong lateral velocity variation of the low velocity layer (LVL) and the surface layer results in the serious problem of static correction. However, flank disturbance caused by large dune in the seismic data is very severe, which leads to the decrease of signal-noise ratio of seismic data. Flank disturbance and dispersion of high energy submerge the signals. The reflection signals are hard to be seen in some raw single-shot records.
According to the features of seismic data in this region, the article emphasizes on static correction and pre-stack de-noising, which aims to eliminate static correction caused by complex dunes and some noise disturbances to increase the signal-noise ratio of seismic data.
On the aspect of solving static correction problem, we adopt the matched static correction technique. Firstly, we summarize the new equations of dune curve to solve the long wavelength and medium wavelength static problem. Secondly, we adopt mutual refraction statics technique to solve the large residual statics. Finally, we adopt offset-division surface consistence residual statics method to solve the discrepancy problem of residual statics from different offset in the common reflection gathers.
On the aspect of prestack de-noising, we adopt the technique of median filtering, adaptive low frequency noise suppression, and high-energy disturbance suppression to suppress the different noises respectively. Meanwhile, according to the different linear relationships and strong-weak relationships among different“fields”, we apply the methods to different datasets in series and achieve a better processing results.
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