【摘要】 如今众多的薄层定量描述方法通常基于Widess模型,利用地震属性能识别地层厚度小于四分之一地震波长(λ/4)的孤立薄层。然而实际工作中通常遇到的是一套薄互层,其中单个薄层的厚度往往远小于λ/4,应用现有地震方法难以分辨每个薄层。本文通过构建楔状薄互层模型研究薄互层调谐规律,建立了薄互层地震响应与薄互层参数之间的联系,提出了薄互层净厚度估算方法。文章首先提出地震视净毛比概念,并在研究薄互层调谐规律的基础上提出了去调谐算法,然后将薄互层地震响应经过去调谐转化成视净毛比,再通过视厚度与视净毛比相乘计算出净厚度。文中选用具有地层波阻抗意义的90°相位子波地震数据解释薄互层储层,并研究了90°相位子波的去调谐算法,能将90°相位子波地震振幅较准确地转化为视净毛比。四川广安地区须四段薄互层实例预测结果表明,本文提出的净厚度估算技术能有效预测河道三角洲相含气砂体的平面展布。更多还原

【Abstract】 Today a large number of methods for description of a thin layer are normally based on the Widess model.Seismic attributions like maximum amplitude or dominant frequency are usually used to recognize a thin layer less than λ/4.However,the target what we face in real exploration is usually a suit of interbedded sand/shale layers,each of which we can not recognize using seismic methodology.In this paper a laminated sand/shale wedge model is constructed to investigate the regularities of tuning effects of thin interbedded layers.The relation between seismic reflection characteristics and thickness parameters of the thin interbedded layers is built up.Then a method on net thickness estimation for thin interbedded reservoirs is presented.Importantly,the conception of seismic apparent net to gross is proposed,which can be acquired from seismic response of thin interbedded layers,using a detuning algorithm based on regularities of seismic tuning effects.Here 90° phase wavelet response with interests of impedance is chosen to interpret thin interbedded reservoirs.After the detuning algorithm for the 90° phase wavelet is deduced,apparent net to gross can be obtained from the real 90° phase wavelet response.Thus net thickness can be calculated by multiplying apparent thickness by apparent net to gross for the thin interbedded reservoir.The real forecast for the thin interbedded reservoir of Xu-4 member in Guang’an,Sichuan reveals the method on net thickness determination can be used to characterize the distribution of gas sand of channel facies or delta facies.更多还原