【作者】 周晨光；

【导师】 韩立国；

【作者基本信息】 吉林大学 ， 地球探测与信息技术， 2007， 硕士

【摘要】 共反射面叠加(CRS)提供一种从多次覆盖反射数据进行零偏移距模拟的方法,它不依赖于先验速度信息。对二维资料应用共反射面叠加,可产生CRS叠加面,它依赖于三个参数,它们是零偏移距射线的出射角α,以及与零偏射线有关的两个波前曲率半径R N和R NIP,即法向波和法向入射点波的波前曲率半径。对自激自收剖面上的每一个样点可确定一组最佳参数,这组参数能使CRS走时面最好地拟合反射同相轴。确定三参数的过程是反复搜索和寻优的过程,所以这里将涉及到从一维到三维的寻优算法。此文以两种途径,分别应用多种最优化方法进行三参数的寻优,并对结果、实现效率进行分析,得出其一种途径因应用了全局最优化算法而更可取,并将其应用到实际数据,得出的剖面浅层效果比较好。更多还原

【Abstract】 The seismic survey is the most effective prospecting geophysical method during exploration and development of oil/gas. The structure and the lithology of the geological body become increasingly complex now. So it must assure that the seismic section own upper resolution if we need accurately describe the targets. High signal/noise ratio is the precondition of high-resolution.Common-Reflection-Surface (CRS) stack is the best way at present to simulate zero-offset section. Common Reflection Surface is a circle segment around an underground reflector. Its travel time response in the time domain, which is CRS stack surface, can be regraded as a combination of all Common Reflection Point (CRP) trajectores in the segment. CRS stack can focus more energy in the vicinity of the reflector, therefore can obtain a better zero offset section by stacking events with same phase.The notable advantage of CRS stack Fresnel zone, and select method and it is the valid seismic data is that it can calcalate the stack area using Projected to stack. This process of selection is like usual DMO method.At first, based on wave equation, high-frequency ray solution and its character are given to clarify theoretical foundation of the method. The hyperbolic and parabolic travel time of the reflection in layer media are presented in expression of matrix with paraxial ray theory. With geometrical optics, the relationship between object point in model and image point in image space is built for the complex subsurface. The travel time formula of reflective point in the monunifonn media is deduced. Also the formula of reflective segment of zero-offset and nonzero offset section is provided.For 2-D acquisition, the CRS stack leads to a stacking surface depending on three search parameters. The optimum stacking surface needs to be determined for each point of the simulated zero-offset section. For a given primary reflection, these are the emergence angleαof the zero-offset ray, as well as two radii of wavefront curvatures R N and R NIP.They all are associated with two hypothetical waves:the so-called normal wave and the normal-incidence-point wave. We also addressthe problem of determining an optimal parameter triplet(α, RNIP, RN) inorder to construct the sample value(i.e.,the CRS stack value)for each point in the desired simulated zero-offset section.This optimal triplet is expected to determine for each point the best stacking surface that can be fitted to the multicoverage primary reflectionevents.To make the CRS stack attractive in terms of computational costs, a suitable strategy is described to determine the optimal parameter triplets for all points of the simulated zero-offset section. For the implementation of the CRS stack, we make use of the hyperbolic second-order Taylor expansion of the stacking surface.This representation is not only suitable to handle irregular multicoverage acquisition geometries but also enables us to introduce simple and efficient search strategies for the parameter triple.In specific subsets of the multicoverage data(e.g.,in the common-midpoint gathers or the zero-offset section),the chosen representation only depends on one or two independent parameters,respectively.So we present two optimization strategy for estimating these three parameters and simulating a zero-offset section through CRS stacking formalism.by different optimized methods such as variational simulated annealing algorithm,patternsearch algorithm and so on.Finally, the processing of practical data is successful though existing the dip discrimination phenomenon.更多还原