激电效应对AMT正演的影响及其在砂岩型铀矿中的数值模拟
Influence of induced polarization effects on AMT forward modeling and its numerical simulations for sandstone uranium deposits
胡英才 1王瑞廷 2李貅3
作者信息
- 1. 西北有色地质矿业集团有限公司,陕西西安 710054;长安大学地质工程与测绘学院,陕西西安 710061;核工业北京地质研究院 中核集团铀资源勘查与评价技术重点实验室,北京 100029
- 2. 西北有色地质矿业集团有限公司,陕西西安 710054;长安大学地质工程与测绘学院,陕西西安 710061
- 3. 长安大学地质工程与测绘学院,陕西西安 710061
- 折叠
摘要
音频大地电磁测深法应用比较广泛,已成为固体矿产深部地球物理探测的主要方法之一,但在处理解释中,往往只考虑电磁效应,忽略了激电效应,这与实际地质情况不相符.本文在实现带激电效应的二维音频大地电磁有限元正演基础上,模拟了激电效应各参数对二维正演响应的影响大小及规律,同时对二连盆地砂岩型铀矿的地电模型进行了数值模拟研究.结果表明:①基于Cole-Cole模型实现的带激电效应二维AMT正演,随着极化率、频率相关系数及时间常数取值的增加,主要降低二维正演视电阻率异常响应值,增大阻抗相位异常响应值,这对探测低阻目标体有利,探测高阻目标体影响较大;②激电效应中的零频电阻率和极化率对二维正演响应影响较大,频率相关系数与时间常数对正演的影响大小主要取决于极化率,当极化率较大时,二者对正演响应同样具有较大的影响;③在砂岩型铀矿中,当砂体中存在浸染状及含硫化物的岩性时,较大的激电效应会对频域电磁测深法探测目标砂体产生较大影响,因此在探测前需进行正演建模,了解激电效应的影响大小.
Abstract
The extensively applied audio magnetotellurics(AMT)has become a primary method for deep geophysical exploration of sol-id mineral resources.However,its data processing and interpretation often only consider electromagnetic effects but ignore induced po-larization(IP)effects,which is inconsistent with actual geological conditions.Based on the two-dimensional AMT finite-element for-ward modeling with IP effects,this study simulated the magnitude and regularity of the influence of various parameters of IP effects on the two-dimensional forward response.Moreover,this study conducted a numerical simulation on the geoelectric model of sandstone u-ranium deposits in the Erlian Basin.The results show that:(1)With an increase in the values of polarizability,frequency correlation coefficient,and time constant,the two-dimensional AMT forward modeling with IP effects based on the Cole-Cole model primarily re-duced the abnormal response value of two-dimensional forward modeling apparent resistivity and increased the abnormal response value of impedance phase.This is beneficial for detecting low-resistivity targets rather than high-resistivity targets;(2)The zero-frequency resistivity and polarizability in IP effects exhibit a significant influence on the two-dimensional forward response.The influence of both frequency correlation coefficient and time constant on the forward response primarily depends on the polarizability.High polarizability suggests their significant influence on the forward response;(3)In the case of disseminated and sulfide-bearing lithologies in the sand bodies of sandstone uranium deposits,greater IP effects will significantly influence the detection of target sand bodies using frequency-domain AMT.Therefore,forward modeling is necessary before detection to determine the magnitude of IP effects.
关键词
音频大地电磁测深法/激电效应/二维正演/砂岩型铀矿Key words
audio magnetotellurics/induced polarization effect/two-dimensional forward modeling/sandstone uranium deposit引用本文复制引用
基金项目
西北有色地质矿业集团博士后科研工作站项目(XBDKKJ202111)
国家自然科学基金(41604126)
出版年
2024
国家科技期刊平台
NSTL
万方数据