【作者】 邬静；

【导师】 李录明；

【作者基本信息】 成都理工大学 ， 地球探测与信息技术， 2010， 硕士

【摘要】 油气检测和油藏描述中,介质的弹性参数十分重要,这些参数与地层岩性和流体性质有关。描述地层岩性的最主要的3个参数是纵波速度、横波速度和密度,叠前反演是定量求取这三个参数的有效方法。本文以地震波传播理论为基础,以模拟退火和遗传算法为工具,对多波叠前非线性反演进行研究,反演所用数据为带有入射角的叠前多波动校道集。首先对单层参数做反演,利用已知的上层参数和反射界面的AVA曲线递推反演下层参数。在初始模型远离真值的情况下,仍可以得到精度较高的下层参数。但这种递推的反演方式对上层参数有强依赖性,反演效率低,不利于多层的推广。出于适用性和效率的考虑,进一步建立了多层模型,以角道集的误差函数作为目标函数,实现基于波形的多层参数同步反演,反演结果仍具有不依赖于初始模型的优势。通过计算参数扰动所对应的扰动响应,分析了参数的敏感性特征,论证了目标函数的可行性。为了适应多参数的同步优化,对算法和模型做了改进,包括:①对模拟退火算法增加了快速热浴、记忆保优、回温退火,并将经典退火改为非常快速模拟退火;②将遗传算法的实数编码改进为更适用于地球物理反演问题的五进制编码机制。③改进方案采用层和样点的递进模型,样点模型主要针对层位,以确定反射界面为目的,层模型则针对层参数值的精确反演,根据两种模型的特点进行模型的递进反演;④将纵横波进行联合反演,与单一波型反演相比,能有效提高反演精度,尤其是横波速度的反演精度。改进后的方案对单界面、多层等多种理论模型均有较高的反演精度,反演对初始模型依赖性低、抗噪能力较强,对实际资料有一定的反演能力。反演所得参数能为线性和广义线性反演提供高质量的初始模型,也可以为油藏描述提供参考。更多还原

【Abstract】 The elastic parameters of formation are related with lithology and fluid properties, so they are very important for hydrocarbon detection and reservoir description. P-wave velocity, S-wave velocity and density are three main parameters which can descript the formation. In addition, Pre-inversion is an effective method to obtain the value of these three parameters.On the background of seismic wave propagation theory and adopting the simulated annealing and genetic algorithm, this thesis researched the multi-wave pre-stack nonlinear inversion. The data used for the inversion is multi-wave pre-stack NMO gathers.First, this thesis inversed the parameters of single layer-model by using the parameters of upper-layer and the AVA curve of the reflector to inverse the parameters of under-layer. Even the initial model is far from the true one, high precision parameters can still be obtained. But the inversion method has a strong dependence on the upper parameters, and its efficiency is so poor that can’t apply to the inversion of multi-layer.Considering the applicability and efficiency factors, multi-layer model has been established. This model used the error function of angle gather as the objective function to achieve simultaneous inversion. The result of inversion shows it has the advantage of not relying on initial model. According to computing response of every parameter’s disturbance, the sensitivity of parameters has been analyzed. Furthermore the feasibility of the objective function has been demonstrated.In order to adapting the simultaneous optimization of multi-parameter, this thesis made some improvement for algorithms and model which are as follows: (1) The improvements on SA including fast heat-bath, returning temperature strategy, memory function and changing the classical SA to very fast SA. (2) Switching float encoding to quinary encoding mechanism which is more suitable for geophysical inversion problem to improve GA. (3) The improved method adopted sample points model and layer model, the sample point model focused on layer and aimed at determining the reflection interface, layer model focused on inversing high accuracy parameters of layers. Combining the advantages of these two models can realize progressive inversion. (4) This thesis also jointed PP-wave and PSV-wave to realized inversion. Compared to the sole-wave inversion, joint inversion can improve the accuracy, especially for the S-wave velocity.The improved inversion method has high accuracy for a variety of theoretic models. It has low dependence on the initial model and strong resistance to noise. It can be applied to the real seismic data and get good inversion result. The inversion results can provide a high-quality original model for linear and generalized linear inversion; also it can give a reference for the reservoir description.更多还原