中国西部复杂山地山前带地震勘探应用技术研究

【作者】 苟量；

【导师】 贺振华； 黄德济；

【作者基本信息】 成都理工大学 ， 地球探测与信息技术， 2005， 博士

【摘要】 近几年来,随着勘探装备的改进,促进了地震勘探技术的进步,增强了地震勘探技术攻关的能力,加快了油气勘探的步伐,使得找油找气的领域已经向复杂山地地区延伸。相继在我国西部塔里木盆地库车山地山前带发现了如克拉2和迪那2等油气田,预示了复杂山地地区具有良好的石油勘探前景。 然而,在这类地区有两个方面的问题制约着地震勘探。一是复杂的地表条件,地表起伏剧烈,沿地表岩性变化大,老地层出露地表(且伴随不同的角度变化)或是巨厚的砾石层;二是复杂的地下地质构造,特别是库车山地区断裂发育、地下逆冲高陡构造;这两个因素造成了地震波场复杂,规则噪声能量强,地震反射信号能量弱,使得地震勘探非常凼难。本文从山地地震勘探的关键技术入手,即影响地震数据品质最关键的三个因素:反射信号能量吸收和衰减、静校正和规则噪声。 论文的第一部分针对提高有效反射波能量的激发和接收因素开展研究,在激发方面:从增强弹性波能量的炸药爆炸机制出发,系统研究了影响冲击波能量的激发因素,从激发环境上分析激发效果,在井深选择上采用双井微测井确定虚反射界面,分析虚反射对激发子波能量和频率的影响,结合爆炸半径,合理确定激发井深;在接收方面:围绕如何合理避开“地震窗”,提高地下反射信息的接收量,采用物理模型方法进行分析,合理地解决了逆冲高陡构造优化观测问题,包括观测系统形式、道距和覆盖次数等参数的选择。论文的第二部分是静校正方法研究,我们首先建立了合理的表层模型解决长波长静校正问题,再利用初至信息计算相对折射静校正以解决野外静校正问题;提出了在层析反演静校正中引入先验信息约束和调谐式先验信息约束的思路;先验信息约束和调谐式先验信息约束方法提高了常规层析反演静校正方法的收敛速度和反演精度,解决了常规层析静校正中存在的问题。论文的第三部分是压制规则噪声研究,针对西部山地地区非常发育的规则噪声,提出了把二维资料当成是三维资料的特例,采用逐点识别的方法,自动适应规则噪声视速度的任意变化,快速实现了压制二维和三维叠前地震数据上的规则噪声。论文的最后是应用实例,明显的应用效果证明了本文研究的成果能够有效地解决西部复杂山地地区地震勘探中存在的一些关键问题。更多还原

【Abstract】 In the recent years, the improvement of equipment has expedited the development of seismic exploration technologies, enhanced the abilities to attack difficult exploration problems and accelerated the exploration pace. The prospecting has been extending into complex mountain areas. The discovery of Kela-2 and Dina-2 oil & gas fields in Chuche basin west China indicates that there is great potential in complex mountain areas.However, there are two main issues that hinder the seismic exploration. The first one is the complex surface conditions, for instance the rugged landforms, rapid lithology variations, outcrops with conflicting dip angles, or thick gravel layers. The second one is the complexity of the subsurface structures, say, deeply faulted or steeply dipping overthrusts, especially in Chuche basin. All these complicate the seismic wave fields, cause strong coherent noises and weaken reflections, and thus, make the seismic exploration a very difficult task. This paper presents key techniques related to the three most crucial factors that influence seismic data quality, namely, reflection energy absorption and decay, statics and coherent noises.The first part is about how to get sufficiently strong reflections in data acquisition. In the shooting aspect, the various factors related to excited energy, such as explosion mechanism, shooting lithology, shot depth etc., are studied. In the recording aspect, focusing on how to record as much as possible reflected energy and reasonably avoid the "seismic barrier’, acquisition geometries including spread pattern, group interval and fold coverage are studied and with the help of a physical model, a reasonable and optimum acquisition geometry for a steeply dipping overthrust is designed. The second part is on the research of static correction methods. A reasonable near-surface model to solve long-wavelength statics problem is first built, then refracted first arrivals are used to compute relative statics to solve the field statics problem. We also developed a priory information constrain method and a ’scanning-style’ priory information constrain method in tomographic statics inversion. These two methods give higher convergence speed and inversion precision and therefore, solved the problems in conventional tomographic statics inversion. The third part is the research on coherent noise attenuation. According to the variety of strong coherent noises in the data of west China, a 2-D data is processed as a special 3-D data. A ’point-by-point’ auto-adaptive noise discrimination method was used to attenuate coherent noises in pre-stack 2D and 3D data. Real data examples are finally shown. The obvious effects show that the research results of this paper can effectively solve the crucial problems in the seismic exploration in complex mountain areas of west China.更多还原