基于伽马能谱的元素测井发展历程及技术展望

随着对油气勘探开发的不断深入,勘探对象复杂,给测井解释评价带来极大的挑战.基于伽马能谱的元素测井是通过测量地层元素自发产生或中子源激发的次生伽马能谱,利用谱解析方法获得地层元素含量,为复杂储层测井评价提供一种有效手段.本文全面归纳总结了伽马元素能谱测井的发展历程,认为其可分为四个大的阶段:自然伽马能谱测井、地球化学测井、元素俘获能谱测井和基于脉冲中子源的元素能谱测井;并对其测井技术进行展望,认为基于伽马能谱的元素测井应遵循"三多"发展趋势,即:多功能仪器设计、多参数成果解释和多方位近钻头测量.     

基于Monte-Carlo模拟的元素俘获能谱测井中元素谱特征分析（英文）

为了使用简易的方法获取可靠的单元素伽马能谱,本文针对元素俘获能谱测井仪器单元素中子伽马能谱的获取进行了仿真模拟计算,包括中子源的选择、地层模型的设计以及探测器的布置。采用Monte Carlo方法中具有代表性的MCNP(Monte Carlo N-Particle Transport Code System)程序模拟了Am-Be中子源产生的中子经过慢化后与地层元素发生热中子俘获反应的中子和光子的输运过程,记录了元素的特征γ射线和伽马能谱,获得的了十种元素的中子俘获伽马能谱。经过对比分析,模拟计算结果与斯伦贝谢公司公布的单元素标准γ能谱在特征峰位位置及谱形变化方面具有很好的一致性,且主要特征峰位所在的位置与国际原子能机构核数据中心数据一致,用实际测量谱验证表明了利用该方法获得的中子伽马能谱具有较强的实用性,对于元素俘获能谱测井数据处理的深化研究具有一定的实用价值,同时也为其他类型元素测井仪器数据处理提供了重要的借鉴意义。     

利用俘获伽马能谱确定饱和度的可行性及蒙特卡罗模拟研究

脉冲中子伽马能谱测井是利用多探测器获取非弹性散射伽马、热中子俘获伽马能谱及伽马时间谱,通过C/O和地层宏观吸收截面来确定饱和度,但俘获伽马能谱的信息没有得到很好利用,在地层水矿化度较高的情况下,由于俘获伽马能谱的Si,Ca和H的能窗内总的伽马计数与Fe能窗内的伽马计数比值与含氯量有关,因此由俘获伽马能谱确定含水饱和度是可行的,利用MCNP(蒙特卡罗方法)模拟研究了三能窗计数与Fe能窗计数比值与饱和度、岩性、孔隙度、泥质含量、井眼持水率、地层水矿化度以及井眼套管等条件下的关系,为在高矿化度地区利用俘获伽马能谱确定饱和度的可行性在理论上提供了支持.     

基于元素俘获能谱测井的多矿物最优化处理方法(英文)

计算地层岩石矿物组分并形成连续变化的岩性剖面是测井解释的核心工作之一。相对于传统的POR、CRA等处理方法,最优化方法能够利用各类测井、地质信息进行综合求解,适用范围更广、计算精度更高。元素俘获能谱测井可以提供多达9种常见地层元素的重量百分含量,使得岩性剖面的计算更直接、更准确。为了充分发挥最优化方法、元素俘获能谱测井的优势,进一步提高岩石矿物组分计算的精度,本文首先确定了不同矿物的元素俘获能谱测井响应方程形式和权重系数计算方法,然后在全岩氧化物实验分析和理论计算的基础上确定了常见矿物的元素含量测井响应值,从而形成了一套完整的基于元素俘获能谱测井的多矿物最优化处理新方法。应用证明,新方法的处理结果与岩心分析结果具有较好的一致性,平均绝对误差在10%以内,其计算精度更高。     

碳氧比能谱测井的蒙特卡罗模拟

介绍碳氧比能谱测井蒙特卡罗模拟方法及软件,内容包括输运计算与探测器响应计算,其中中子诱发y使用了期望值技巧,γ散射采用指向概率法.计算结果可分别给出次级γ线光和连续光,还可给出被探测物或元素的非弹性谱和俘获谱,新方法基本解决了碳氧比能谱测井深穿透、低计数率的难题.     

脉冲中子双伽马谱饱和度测井方法及数值模拟研究

脉冲中子双伽马谱饱和度测井方法是利用特定的脉冲和测量时序设计,采用远、近伽马探测器记录非弹性散射和俘获伽马能谱以及伽马射线时间谱,通过获取C/O和地层宏观俘获截面等信息来确定地层含油饱和度.采用大直径仪器和BGO晶体探测器时,其采集的非弹性散射和俘获伽马能谱计数统计性优于国外仪器,重复脉冲发射中子后伽马射线时间谱仍满足指数衰减规律,且能使伽马射线时间谱的道计数累积,计数统计性好于常规中子寿命测井,得到的地层宏观俘获截面与单脉冲发射近似相同.在地层孔隙度未知的情况下,利用C/O和地层宏观俘获截面交会技术可以定量确定含油饱和度.     

基于时频分析的中子非弹性散射伽马能谱反演方法

本文针对脉冲中子多循环发射过程中测量的非弹伽马能谱受俘获能谱干扰,引起的油水区分度小的问题,提出了利用时间谱和能谱结合获取纯净非弹伽马能谱的方法.通过蒙特卡罗方法建立C/O仪器数值计算模型,模拟不同井眼和地层条件下的伽马时间谱,分析了井眼和地层对伽马能谱的贡献,对比了俘获伽马时间谱理论计算结果和模拟结果,同时利用某油田刻度井实测数据,验证该方法在评价含油饱和度的可靠性.结果 表明:井眼条件是影响伽马能谱的主控因素;利用理论计算的脉冲区内俘获密度和数值模拟结果一致;采用该方法处理某油田刻度井实测数据,C/O对油、水差异反应更加灵敏度,油水动态范围提高;最终实测井数据也验证了该方法的准确性.     

元素测井产额计算及影响因素分析

元素测井是非常规储层测井评价的主要测井方法之一.元素测井是以元素测量为基础,从矿物成分的角度提供地层信息,有效地将测井资料与地质信息结合起来.元素产额获取会受地层矿物和井眼环境的影响.为了提高元素产额计算的准确性,有必要对影响元素产额计算的因素进行分析.本文利用蒙特卡罗方法分析加权最小二乘逆矩阵法在地层矿物相对复杂的情况下求取元素产额时,地层减速作用、地层俘获作用、地层密度与井眼尺寸对元素产额计算精度的影响.研究结果表明,地层密度对元素产额计算的精度影响较大,地层密度越低,地层元素之间的相互影响越大,使得元素产额计算的误差变大,而元素产额计算受地层减速作用与地层俘获作用的影响较小,仅在地层减速能力较弱或地层俘获作用较强时对元素产额计算有一定影响,井眼尺寸对元素产额计算的精度影响取决于井内介质.     

核辐射测井全能谱分析方法综述

多元素能谱测井通过全能谱分析方法求取单个地层元素的产额,进而求取元素重量百分含量和矿物百分含量,为识别复杂油气藏岩石类型和矿物类型、建立复杂油气藏新的测井解释模型及应用正确评价方法开辟了新的途径,为地质问题和工程问题的解决提供了新的手段,全能谱分析方法研究是当前国内核辐射测井研究热点之一.本文表分析多元素能谱测井的重要...     

测井中子发生器

测井中子发生器作为中子源目前应用于地层岩性、孔隙度、含油饱和度及地层动态监测测井,是C/O测井、中子寿命测井、氧活化水流测井以及脉冲伽马能谱测井等仪器的核心部件.简要介绍了几种国外测井中子发生器的产品.阐述了测井中子发生器的工作原理、基本构成及关键技术.介绍了中国石油测井有限公司测井仪器厂研制生产的中子发生器产品系列.脉冲中子伽马测井是当前油田生产动态监测普遍采用的技术.介绍了实现宽频带、锐截止的技术途径以及目前所取得的成果.中子发生器产额的稳定性及开机重复率指标的提高将会极大拓宽其应用领域,尤其在使用同位素中子源的领域,可以替代同位素中子源发挥独到的优势.介绍了中国石油测井有限公司在中子发生器产额稳定方面所做的工作和取得结果,并列举了稳定产额后的中子发生器在元素分析领域所取得的成功试验.     

Estimating thermal conductivity from core and well log data

The aim of the presented work was to introduce a method of estimating thermal conductivity using well log data. Many petrophysical properties of rocks can be determined both by laboratory measurements and well-logs. It is thus possible to apply geophysical data to empirical models based on relationships between laboratory measured parameters and derive continuous thermal conductivity values in well profiles. Laboratory measurements were conducted on 62 core samples of Meso-Paleozoic rocks from the Carpathian Foredeep. Mathematical models were derived using multiple regression and neural network methods. Geophysical data from a set of seven well logs: density, sonic, neutron, gamma ray, spectral gamma ray, caliper and resistivity were applied to the obtained models. Continuous thermal conductivity values were derived in three well profiles. Analysis of the obtained results shows good consistence between laboratory data and values predicted from well log data.     

STATISTICAL MULTIVARIATE ANALYSIS OF AIRBORNE GEOPHYSICAL DATA ON THE SE BORDER OF THE CENTRAL LAPLAND GREENSTONE COMPLEX*

Statistical multivariate methods for the integrated processing of airborne geophysical data were tested. The data consisted of magnetic, electromagnetic and gamma radiation measurements, to which cluster analysis, principal components analysis and discriminant analysis were applied. Also, auxiliary variables were derived from the original ones and their value was tested. Although the frequency distributions of the data do not favour statistical analysis, the practical results are acceptable. Principal component analyses show geological and technical aspects that are difficult to obtain from the original observations. In cluster analyses, the sources of measured fields control the grouping of variables. Discriminant analysis was applied to the automatic identification of rocks by geophysical data. The rocks investigated are metasediments and metavolcanics, some magnetic and others conductive. When all available geophysical data were included, correct identifications were made in more than 60% of cases. In particular, gamma ray observations were found to improve the discrimination of non-magnetic and non-conductive rocks. The geophysical similarity of rocks studied by cluster analysis depends on electrical and magnetic properties as well as on their origin; the content of radioactive elements in turn is related to the origin.     

A heuristic model of three-dimensional spectra of temperature inhomogeneities in the stably stratified atmosphere

Many measurements have shown that the random temperature fields in the stably stratified atmosphere are not locally isotropic (LI). The local axial symmetry (LAS) hypothesis looks more appropriate under these conditions. The object of this paper consists in the development of a flexible tool for spectral studies of LAS scalar fields independently of their origin in stably stratified geophysical flows. A heuristic model of a 3D spatial spectrum is proposed in order to describe and study statistical properties of LAS temperature inhomogeneities from LI structures up to quasi-layered ones. To simplify the solution of this problem, a main assumption was accepted: the consideration is restricted to 3D spectra which may be given on a one-parametric family of surfaces of rotation. Such 3D spectra may be represented by a single function of one variable which is the parameter of the family. This approach allows one to introduce the generalized energy spectrum which describes an energy distribution according to inhomogeneity sizes. The family of surfaces determines the shape of inhomogeneities. The family of ellipsoids of rotation and power-law generalized energy spectrum is used as the simplest example of the model application in order to study the general properties of LAS-structure spectra. The behavior of vertical, horizontal, and oblique 1D spectra and coherency spectra is studied. The relationship between the suggested model and some existing models of temperature spectra is considered. The application of the model for the analysis of experimental data is shown for two sets of measurements. It is shown that the suggested model may quantitatively describe experimental 1D spectra and coherency spectra from a unique point of view. It is noted that the model may be used for both the planning of measurements and data processing. Possible generalizations of the model are considered for random fields with more degenerate symmetry and for space-temporal spectra.     

电流线追踪电位电阻率层析成像方法初探

电阻率层析成像技术尽管已有了一些比较好的结果，但从国内外发表的文章可以看出，基本上采用的都是有限元方法，而电阻率层析成像的核心问题也就是雅可比矩阵的求取问题。有限元方法能够很好地实现该问题的求解，但需要的计算机内存及计算时间相当的大，为此我们类比地震学中走时射线追踪技术，开展了电流线追踪电位电阻率层析成像方法研究。     

复杂地形条件下航空伽玛能谱地形改正方法探讨

应用矩形辐射体航空伽玛辐射场理论,研究应用于复杂地形条件下的航空伽玛能谱资料的地形改正方法,并针对该方法进行验证. 本文利用航空物探测量过程中获得的DTM数据（达到了地形改正所需的地形起伏数据精度）,应用矩形辐射体航空伽玛辐射场理论,根据地面辐射体与航空伽玛场分布之间的正演关系,对航空伽玛能谱解释方法的原理进行了正演分析和反演推导. 探索出一种按影响角进行地形改正的方法. 该方法特点是适合于任意飞行方式(缓地形和水平飞行均可)和任意地形条件航空伽玛能谱的逐点地形改正. 结果表明该地形改正方法能够基本消除航空伽玛能谱测量中的地形起伏产生的影响,经地形修正后的航空伽玛能谱异常能较正确地反映地面辐射体的真实情况.     

COSMIC大气掩星开环数据反演方法

COSMIC星座GPS无线电掩星探测利用GPS开环接收技术提高低层大气观测数据的质量和对上升掩星事件的跟踪能力.开环掩星观测数据受到GPS导航数据调制的影响,在其数据后处理中必须消除该影响以获得高质量的科学反演结果.利用GPS导航数据调制码数据和利用开环数据本身内在的关系等两种方法可以消除该影响.将上述方法应用于COSMIC的掩星事件个例反演,获得了修复的大气附加相位数据;并利用几何光学近似反演方法和全谱反演方法,获得了射线弯曲角. 全谱反演方法获得的弯曲角及其温度反演结果与COSMIC数据中心的结果一致,说明我们的算法是有效的.     

In‐situ gamma‐ray spectrometric study of weathered volcanic rocks in Hong Kong

In‐situ gamma‐ray spectrometry (GRS) measurements were conducted at 35 sites in Hong Kong where volcanic rocks with varying extent of weathering were exposed. Elemental analyses using X‐ray fluorescence spectrometry and inductively coupled plasma–mass spectrometry were carried out on samples collected from these 35 plus 22 other locations to assess the feasibility of using the GRS method to quantify the extent of weathering. The Parker weathering index, varying within a range of 0·0–0·8 for the samples studied, was used as a geochemically based reference scheme for correlating the gamma‐ray spectrometric results with the extent of weathering. For the former 35 sites, the concentrations of the three major radioelements, K, U and Th, determined by in‐situ GRS were compared to laboratory‐determined values from the samples. The study reveals that no significant change occurs to the contents of the three radioelements during the initial state of weathering. But once the rocks become highly weathered, further progression of weathering is accompanied by a systematic removal of K and an increased dispersion of U and Th. The results show that K content, which is indicative of the extent of weathering, can be retrieved reliably with the gamma‐ray spectrometry technique. The study has given support to the potential use of the downhole spectral gamma method for evaluation of weathering grade and the detection of subsurface clay‐rich levels. Copyright © 2002 John Wiley & Sons, Ltd.     

Optimum pilot sweep

The successful application of high-resolution seismic methods requires evaluating each element in the seismic system and ensuring that each part of the system contributes optimally to the success of the method. Unfortunately, unlike data processing, seismic signal generation is not carefully optimized. The purpose of our study was to optimize the source signal in order to better coordinate field operations with subsequent data processing to achieve their common objective. We developed an iterative method for a rational frequency distribution of the energy of a seismic source. The method allows the optimum amplitude spectrum of a source signal to be calculated, thus providing the best data quality at the end of the processing. We assume that the source signal is affected by a total transfer function, by the reflectivity function of a target interval, and by ambient noise, whose characteristics, if not known, can be estimated or measured in practice. The transfer function includes data processing other than the correlation stage and the final trace-optimizing filter. The variance of a reflectivity estimate is considered to be a measure of the data quality and improvement of the characteristic corresponds to a decrease in the variance. For this reason, a constrained Wiener deconvolution filter is used as the final trace-optimizing filter. It not only minimizes the variance of a reflectivity estimate but also ensures a specific signal-to-noise ratio. The method is made feasible by following the Vibroseis technique, primarily because of the versatility of the technique in controlling the signal spectrum. With the optimum amplitude spectrum obtained, the corresponding optimum pilot sweep can be readily calculated. Examples using synthetic data are presented to illustrate the method.     

基于多射线联合反演的速度无关叠前地震数据Q值估计

描述地震波衰减特征的品质因子Q对地震数据处理和油藏描述非常重要,在地震勘探领域,Q值一般通过垂直地震剖面(VSP)数据或地面地震数据得到.由于叠前地面地震数据具有复杂的射线路径且存在噪声、调谐干涉效应等影响,从叠前地震数据中准确估计Q值相对困难.本文以地震波射线传播为基础,根据同相轴局部斜率和射线参数的映射关系,将多射线波形频谱同时带入谱比法联合反演估计Q值,提出了基于多射线联合反演的速度无关叠前Q值估计方法.该方法通过局部斜率属性避开了速度对Q值估计的影响,局部斜率携带地震波传播的速度信息,具有相同局部斜率的地震反射波具有相同的传播射线参数.同相轴局部斜率是地震数据域的属性,而速度是模型域的参数,在估计Q值中采用数据域的属性参数可以直接应用于数据的联合反演,而不需要通过速度对其做进一步的转化,从而提高了Q值估计的精度.同时,本方法采用预测映射(predictive mapping)技术将非零炮检距反射信息映射到零炮检距处,从而获得零偏移距走时对应的Q值.模拟和实际算例验证了本文方法的有效性.