四川盆地泸州区块页岩气三维地震覆盖密度优选  

Optimizing 3D seismic coverage density in Luzhou shale-gas block,Sichuan Basin

作　　者：周晓冀 杨智超 杜文军 王雪梅 巫骏 敬龙江 Zhou Xiaoji;Yang Zhichao;Du Wenjun;Wang Xuemei;Wu Jun;Jing Longjiang(Southwest Geophysical Company,CNPC BGP Inc.,Chengdu,Sichuan 610213,China)

机构地区：[1]中国石油东方地球物理勘探有限责任公司西南物探分公司

出　　处：《天然气勘探与开发》2021年第2期93-99,共7页Natural Gas Exploration and Development

摘　　要：页岩气藏高效开发依赖于高精度三维地震资料,而覆盖密度是决定三维地震资料品质和投资成本的关键参数。针对四川盆地泸州区块海相页岩气三维地震资料,在确保对比因素单一性的前提下,通过抽炮排列将覆盖密度由原始的52.5×10^(4)道/km^(2)逐步退化为6种不同覆盖密度的三维观测系统,并对其叠前偏移成果进行定性、定量评价以论证和优选覆盖密度参数;同时对比了相同覆盖密度下大面元高覆盖和小面元低覆盖两种观测系统的优劣。结果表明:①叠前偏移成像效果随着覆盖密度的增大而逐渐改善,信噪比也随之提高,振幅、频率、信噪比的定量评价显示泸州区块页岩气三维地震观测系统覆盖密度选择在42.0×10^(4)道/km^(2)较为合适;②在相同的覆盖密度下,大面元高覆盖观测系统能够提高地震资料的信噪比,有利于复杂构造的成像,而小面元低覆盖观测系统则有更高的纵横向分辨率。结论认为:开展覆盖密度参数退化试验,综合定性和定量评价结果能够获得一个兼顾成像效果和经济性的覆盖密度参数;在覆盖密度确定的前提下,对于信噪比较高地区,可以选择小面元低覆盖观测系统,而对于信噪比较低地区,可以选择大面元高覆盖观测系统。For shale-gas reservoirs,the efficient development relies on high-precision 3 D seismic data,and 3 D coverage density is a key parameter that determines data quality and investment costs.In the 3 D seismic survey on marine shale gas in Luzhou block,Sichuan Basin,the recording geometry was optimized by gradually reducing the 3 D coverage density from the original 52.5×10^(4)/km^(2) to 6 different values through thinning shot array in that premise the contrast factor maintains the same.In addition,some pre-stack migration results were qualitatively and quantitatively evaluated to optimize this density.Furthermore,both good and bad points of two recording systems(one with large bin and high coverage,and another with small bin and low coverage)were summarized at the same density.Results show that:(1)the effect of pre-stack migration image may gradually be improved with the increase of 3 D coverage density,and the SNR is also increased.Quantitative evaluation on amplitude,frequency,and SNR proves that in Luzhou shalegas block,the coverage density of the geometry system is better to be 42.0×10^(4) traces/km^(2);and(2)at the same coverage density,the former geometry system can improve SNR and is beneficial to the imaging of the complex structures whereas the latter one can record seismic data with higher vertical and horizontal resolution.It is concluded that through some tests to reduce the coverage density,combined with comprehensively qualitative and quantitative evaluation,a certain coverage density parameter considering both imaging effect and economy can be obtained.After determining the density,in one area with high SNR,the geometry system with small bin and low coverage should be selected while the geometry system with large bin and high coverage for another area with low SNR.

关 键 词：四川盆地 页岩气 三维观测系统 覆盖密度 参数退化 叠前时间偏移 

分 类 号：P631.4[天文地球—地质矿产勘探]