面向勘探目标基于反射纵波成像照明的VSP采集设计技术

基于VSP技术特点,对VSP采集设计的主要问题进行了探讨,结合实际资料和模拟计算分析,提出了产出/投入比的概念,并针对VSP采集设计如何实现产出/投入最大化问题,提出了面向勘探目标、基于反射纵波成像照明的VSP采集设计思路及实现方法。首先根据密度和速度测井资料或以往VSP速度资料建立1D速度模型,通过AVO分析初步确定最大偏移距选择范围;然后根据该最大偏移距范围,通过改进高斯射线束进行非零偏移距VSP勘探目标反射纵波成像照明模拟,以确定最佳最大偏移距和合适的观测井段;最后根据Walkaway-VSP(WVSP)/3DVSP观测系统,模拟勘探目标的横向覆盖次数及其分布,经过反复调整观测系统及采集参数,使勘探目标所获得的覆盖次数最大、分布最优。通过实际VSP观测系统设计方案对比分析,证明了本文VSP采集设计技术良好的应用效果。

VSP survey design is discussed based on technical features of VSP.The basic concept of output-input ratio is addressed by means of seismic imaging illumination of VSP up-going P-wave.A target-oriented VSP survey design method based on an improved Gaussian beam illumination analysis is proposed to realize output-input maximization.Firstly,a 1D model is established based on density and velocity logging data or previous VSP velocity data.The optimum selection range of maximum offset is determined via AVO analysis.Based on the optimum range of selected maximum offsets,the method then realizes numerical simulation of seismic imaging illumination of VSP up-going P-waves for non-zero offset VSP exploration targets using improved Gauss ray beam,so as to determine the optimum maximum offset and identify appropriate observation well sections.Finally,based on the WVSP/3DVSP observation system,the horizontal folds and its distribution in the target layer are simulated.After repeated adjustment of the observation system and acquisition parameters,the folds of the exploration targets get maximized and optimal distribution is achieved.Comparative analysis of actual VSP observation system design schemes indicates that the proposed design method has a good application potential.

国家科技重大专项“库车坳陷深层-超深层天然气田开发示范工程”(2016ZX05051)资助。