| 岩芯尺度的宽频介电常数频谱实验室测量设备的误差分析及其在物质测量中的应用(英文) |
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| 引用本文： | 张天华,AL-OFI Salah,Mahmood Akbar.岩芯尺度的宽频介电常数频谱实验室测量设备的误差分析及其在物质测量中的应用(英文)[J].地球物理学进展,2012,27(2):582-595. |
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| 作者姓名： | 张天华 AL-OFI Salah Mahmood Akbar |
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| 作者单位： | 斯伦贝谢碳酸盐研究中心,SDCR,Dhahran Techno Valley-KFUPM,P.O.Box 39011,Dammam/Doha Camp 31942,沙特阿拉伯 |
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| 摘 要： | 宽频介电常数频谱测井技术最近被引进石油工业.这种新技术区别于传统介电常数测井技术在于多频率频谱的测定和利用.高频谱端包含介质油水饱和度信息,而低频谱端对介质中孔隙结构和水的分布形态很敏感.这种新技术可以有效地被应用于比如超淡水介质或者超黏度重油等对于常规测井来说是很困难的测量环境,而且受介质水中的含盐度影响很小.随着井下测井仪器的投入使用,相应的实验室岩芯测定设备和方法就变得重要起来.因为实验室环境相对较为稳定和可控,实验室岩芯测量结果是对井下测量的很好地验证和校订.文献中记载了许多非破坏性的实验室介电常数的测量设备,然而这些设备的共同局限性是它们对岩芯尺寸和岩芯样本的要求和限制,一般要求粉末状岩芯或者一厘米左右的小柱状岩芯.在碳酸盐介质中,非均匀性和各项异性非常普遍,小的岩芯样本能否涵盖井下设备测量尺度(1.5英寸)的特性很值得商榷.本文中介绍了一种最新设计的实验室大直径宽频介电常数测量设备.这个设备可以直接测量石油工业传统的1.5英寸岩芯样本,测量是非毁坏性的,也就是测量后的岩芯样本可以直接用于其它实验室测量设备,比如电阻率测量或核磁共振测量等.大量重复性试验测得的介电常数色散频谱的精确度对于低损耗介质在2%以内而对于高损耗介质在对孔隙度和含盐度校正以后精确度在3%.文中详细介绍了测量设备所使用的反演程序的算法模型,以及反演误差的算法.反演最后的误差可以用来做数据质量的评定.该测量装置被用于许多物质的测定.测定物质的数据库中合成石英(fused quartz),Teflon,合成陶瓷以及单晶硅的介电常数值可以在文献中找到.该设备的测量结果与文献参考值相符合,说明了该设备测量结果的可靠性.该设备还测量了矿物晶体碳酸钙,晶体白云石以及晶体硬石膏的介电常数,这是常见的碳酸盐介质的主要成分.这些测量给出了碳酸盐介质的边界成分区域值作为参考.该设备测量的两个单晶硅柱状样本的介电常数频谱特性发现退火会改变晶体的结构提高强度,同时会改变介质介电常数的特性.同时矿物晶体碳酸钙测量值高于粉末状测量结果也说明晶体结构可能会导致介电常数测量的不同.该设备具有1.5英寸的大尺度,因此具有和井下设备相仿的测量范围,因而不受介质水平各项异性的影响.但另一方面,该设备仍可以研究垂直各项异性.垂直各项异性的主要原因可能是化学成分不同,孔隙结构不对称或者温度对水分布的影响等等.在对岩石地面露头采样的研究中,宽频介电常数频谱实验室设备检测出了岩芯垂直各项异性,通过对比核磁共振一维孔隙度剖面结构发现总孔隙度不均衡以及分布不对称为该各项异性的主要来源,并且被CT图像所证实.
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| 关 键 词： | 宽频介电常数频谱设备 宽频 各项异性 频率色散曲线 碳酸盐 |
Error quantification of a plug scale lab dielectric spectroscopy setup and its application in material characterization |
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| ZHANG Tian-hua
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AL-OFI Salah
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Mahmood Akbar.Error quantification of a plug scale lab dielectric spectroscopy setup and its application in material characterization[J].Progress in Geophysics,2012,27(2):582-595. |
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| Authors: | ZHANG Tian-hua AL-OFI Salah Mahmood Akbar |
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| Institution: | ZHANG Tian-hua,AL-OFI Salah,Mahmood Akbar(Schlumberger Dhahran Carbonate Research Center,Dhahran Techno Valley-KFUPM,P.O.Box 39011,Dammam / Doha Camp 31942,Saudi Arabia) |
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| Abstract: | Wide band Dielectric Spectroscopy has been newly introduced in oil industry.Dielectrics measurement is acting on water molecules and sensitive to pore water content and distribution in all the salinity range.In this case,application of Dielectric Spectroscopy is important in difficult environment such as fresh water or heavy oil.With the introduction of downhole logging device to measure multi-frequency dielectrics,the requirement of an adequate lab measurement device on similar petrophysical parameters with similar measurement physics becomes important and with high priority.There are non-destructive dielectric measurement devices available in the literature.However the major limitation of those devices is the sample measurement volume.Those devices either work on powder samples,mm-range thin discs or 1 cm range small cylindrical plugs.In carbonate heterogeneity can act in a wide range of scale and modify petrophysical parameters greatly.In this case,the small-sized sample measured properties may not be representative enough for the 1.5-in diameter rock plug,which is the oil industry standard plug size. In this paper we will present the frequency response pattern and error quantification on a non-destructive device that is able to measure Dielectric Spectroscopy on the standard 1.5-in or even larger diameter rock plugs.The detailed characterization of the device presented in this paper shows that the repeatability of this device is within 2% of the material dielectric constant value for dry rock plugs and 3% of material value for wet rock plugs.Error bar can also be given on dielectric dispersion curves as a quality control.Application of this device reveals that frequency response of dry,low loss material is not the same as brine saturated high loss material.The algorithm used in the inversion and its error analysis is presented in detail in the paper. Different types of materials are measured with this large probe.The measurement on fused quartz,Teflon,ceramics and silicon materials matches the value of literature,which gives confidence of our setup.The measured value of calcite,dolomite and anhydrite provides good estimation end points for calcium carbonate rocks with complex lithology.In the literature the values of these minerals are in a variation range and difficult to use for oil industry.The measurements on two artificial mono-crystalline Silicon plugs,one with annealing and one without,reveals the pissibq sensitivity of dielectric spectroscopy on molecular structure variation.The measured dielectric constant on calcite crystal has larger value than literature which is usually measured on powders also agrees with the assumption that crystal size may have effect on dielectric constant value. Although the device is large-bore that can overcome horizontal heterogeneity effect imposed by carbonate sample size,manipulating the lab measurement and interpretation still allow us to identify vertical heterogeneity existed on the core plug.The heterogeneity can be caused by lithology distribution,pore system distribution,temperature etc… The case study result on carbonate outcrops presented in this paper shows that porosity heterogeneity existed in the upper part of the rock plug compared to the lower part of the same plug is captured by Dielectric Spectroscopy measurement and confirmed by NMR 1D profiling porosity distribution and CT-scan image. |
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| Keywords: | dielectric spectroscopy wide-band heterogeneity dispersion curves carbonates |
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