重庆科技学院翻译 - 图文

RUSSIAN LOG INTERPRETATION F. Verga, P.P. Rossa, Politecnico di Torino, M. Piana, M. Gonfalini, ENI-AGIP Division

Copyright OMC 2001.

This paper was presented at the Offshore Mediterranean Conference and Exhibition in Ravenna, Italy, March 28-30, 2001. It was selected for presentation by the OMC 2001 Programme Committee following review of information contained in the abstract submitted by the authors. The Paper as presented at OMC 2001 has not been reviewed by the Programme Committee.

ABSTRACT

The assessment of the reservoir oil or gas in place depends significantly on the accuracy of resistivity data and on the reliability of their interpretation. However, the evaluation of the formation resistivity from Russian BKZ logs is very troublesome for western oil companies as the western interpretation

approach, based on laterolog measurements, is not suitable for the Russian tool characteristics and measures. Resistivity log data recorded in three Russian wells, for which a pronounced inconsistency was found between the water saturation values obtained according to the western interpretation method and the nature and rates of the produced fluids during well testing, were also interpreted applying the

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Russian methodology and a software, named Rt-Mod , suitable for interpretation of Russian logs. The Russian method involves a manual comparison between experimental resistivity measurements and theoretical type curves to obtain formation resistivity, invaded zone resistivity and invasion

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diameter. The Rt-Mod software performs a numerical resistivity simulation based on an inversion method used to generate formation and invaded zone resistivity profiles.

Resistivity values obtained from both methodologies appear to be reliable, and more consistent with well testing results than those obtained when the western interpretation was applied. In particular, the Russian approach appears to be very reliable when layers are thicker than two meters and allows the evaluation of the formation resistivity and invasion diameter also when deep mud invasion is present. However, the Russian approach is complex and very time consuming. Results obtained from the

software application are fairly consistent for any layer thickness. The numerical simulation is very quick, simple, and only requires few data to run log interpretation. However, calculated mud resistivity values are not always consistent with the reported fluid property.

INTRODUCTION

As a consequence of the major political and economical changes which recently occurred in the

countries formerly part of the Soviet Union, western oil companies have expanded their interest in these areas. However, investment planning and reservoir exploitation strategies require evaluation of the

available hydrocarbon reserves. Western oil companies must rely on information gathered with Russian tools and methodologies but then use different criteria for reservoir exploitation. In fact, a deep diversity exists between the Russian countries and the rest of the world, also arising from a cultural and linguistic barrier. At the same time there is a strong need to compare the respective experiences and to define common methodologies. This research was meant to help define a reliable procedure to interpret

Russian logs because logs are fundamental in the determination of the petrophysical properties of the reservoir rocks. In particular, the possibility of achieving a more accurate interpretation of the Russian resistivity logs (BKZ logs) was explored, because western methods, based on the laterolog tool

response, had failed to provide reliable results, mainly due to the differences between the Russian and the western instruments. In fact, the water saturation profile calculated as a function of the true

formation resistivity evaluated by western interpretation, was inconsistent with the nature and quantity of produced fluid during well testing.

The Russian methodology for resistivity log interpretation is entirely manual and is based on the

comparison between experimental resistivity points and theoretical type-curves and, therefore, it can be rather approximate. A new software was developed for resistivity modeling of the Russian resistivity logs, thus allowing a fully automatic interpretation of the registered log curves.

Water saturation values were calculated as a function of the true resistivity values obtained by application of different interpretation methodologies and as a function of different porosity

measurements with the aim to define a correct interpretation procedure and highlight possible error sources in reserve evaluation when interpreting Russian logs.

RUSSIAN TOOLS

The determination of the water saturation profile of a producing layer is based on the formation

resistivity, also called true formation resistivity, which is estimated by interpreting a series of apparent resistivity logs. In fact, direct measurement of the true formation resistivity is hampered by well logging due to bore-hole, mud, and mud filtrate invasion effects.

The minimum logging suites run in the majority of Russian wells typically comprise electrical, caliper, temperature, and gamma ray devices, which occasionally can be complemented by neutron-gamma, density, or acoustic porosity measurements. The minimum logging suites generally comprise less instrumentation than do the European correspondent suites and, except for the omission of an explicit porosity tool, are comparable with those run onshore in the USA before 1985. In general, log data presentation exhibits poor quality and most log hardcopies are black and white and hand-edited.

Western companies have tried to digitized Russian logs but results were sometimes disastrous due to differences in the test procedures, problems related to log and depth scales, and lack of a systematic log quality control, not to mention language problems. Furthermore, several log curves are often combined on the same plot track, which can render the resulting product difficult to understand (Harrison, 1995).

In URSS the evaluation of the true formation resistivity, Rt, is based on measurements recorded using lateral devices. Different lateral measurements (BKZ logs) are combined, using different electrode spacing thereby investigating different depths away from the well bore. Typical suites are composed of five or seven different tools characterized by spacing ranging from one half meter to eight meters. The layer limits are identified and positioned according to the response curve of the short-spaced lateral tools whereas a reliable evaluation of true resistivity is obtained on the basis of the response curve of the long-spaced lateral tools.

The analysis of the lateral measurements is complicated by the asymmetric response of the displayed

curve that does not allow evaluation of an apparent resistivity value (i.e., the measured value)

representative of each analyzed formation. Therefore, an inverted probe (upside-down lateral probe) is frequently run in conjunction with a regular lateral having the same spacing. When suites of resistivity logs include identically spaced BKZ and inverted BKZ curves a “Pseudo-compensated BKZ” gradient log can be obtained by averaging the conductivity read by each curve (Harrison, 1995). This compensated curve is symmetrical, deep-reading and usable in digital processing like induction, focused and normal logs.

Measurements obtained by normal, focused, and induction devices are also employed for Rt evaluation, but only to support and validate results obtained on the basis of lateral measurement analysis. In fact, the tool investigation depth for the induction log does not allow consistent interpretation of log measurements due to a frequently large mud invasion.

RUSSIAN INTERPRETATION

The Russian methodology for resistivity log interpretation allows evaluation of the true formation resistivity, invaded zone resistivity, and invasion diameter. It can be applied to recorded data without any preliminary compensation. The number of different available BKZ logs determines the reliability of the obtained resistivity values. The procedure is entirely manual, and resistivity data correction and interpretation is achieved by repeated and sometimes iterative comparison of the real measurements with appropriate, dimensionless type-curves. In particular, every resistivity value used throughout the interpretation procedure must be normalized with respect to the mud resistivity. However, it is not a standard practice to measure the mud resistivity on the field. It is therefore necessary to evaluate the mud resistivity from the apparent resistivity measurements recorded in low porosity layers.

The methodology requires a preliminary correction of the apparent resistivity values for shoulder bed effects, namely the effects related to the presence of adjacent beds characterized by different electric properties from the investigated layer. Each resistivity value, ??, measured in a limited thickness bed is transformed in the resistivity value of a corresponding ideal layer of infinite thickness (fig. 1). The transformation is performed graphically and requires mud resistivity, ?c, tool spacing, L, and layer thickness, H, to be known.

Fig 1:Transformation of apparent resistivity values to the corresponding values for an ideal

layer of infinite thickness

The ideal apparent resistivity values, ??, obtained by normal, focused, inductive, and lateral

measurements are reported as a function of the tool spacing, L, on the so-called interpretation form (fig 2).

The interpretation form is then superimposed to theoretical type-curves, which describe the apparent formation resistivity, ??, normalized with respect to the mud resistivity, ?c, as a function of the tool spacing, L, normalized with respect to well diameter, d. (fig 3). Each dimensionless curve is also

characterized by a given value of the normalized true formation resistivity, ??. In order to determine the true formation resistivity of the investigated layer the type-curve which best matches the real

measurements reported on the interpretation form must be sought. Since the theoretical curves are specifically derived to interpret lateral measurements, focused, inductive, and normal measurements need to be compared to different curves, called isoresistive curves, which are also plotted on the same chart. The isoresistive curves allow transformation of focused, inductive, or normal measurements into equivalent lateral measurements having the same investigation diameter.

Fig 3:Superposition of real data to dimensionless theoretical curves

Several charts reporting dimensionless type-curve sets similar to that shown in fig. 3 are provided, each characterized by different values of the invaded zone resistivity and invasion diameter. The selection of the most appropriate chart is aided by the use of another chart (fig. 4) reporting dimensionless curves for both the invaded zone resistivity - set A - and the invasion diameter - set B. Superposition of the interpretation form reporting the apparent resistivity values on this chart provides the most probable values for the invaded zone resistivity and the invasion diameter.

Fig 4:Diagram for the selection of the most suitable value of invaded zone resistivity and

invasion diameter. Apparent resistivity values measured by long spaced lateral tools in thin beds are not representative and, therefore, the number of lateral measurements which can be used in the interpretation process is very limited. As a consequence, the log-analyst needs to subjectively supplement this lack of data to achieve interpretation, strongly jeopardizing the interpretation reliability. It is not advisable to apply the Russian log interpretation procedure to layers that are 2 meter thick or less.

NUMERICAL INTERPRETATION

Automatic interpretation of Russian log measurements to determine the true formation resistivity and

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invaded zone resistivity can be performed by using the Rt-Mod software.

The software generates an ideal, two-dimensional geometrical model of the investigated formation and the corresponding synthetic apparent resistivity profile using a finite differences forward modeling. The model is calibrated according to an inverse modeling procedure, i.e., the geometrical and electric properties of the model are progressively modified until a satisfactory superposition between synthetic and real logs is achieved.

Forward and inverse modeling are iteratively repeated until satisfactory convergence is reached. The resistivity values of the invaded and virgin zones assigned to each layer in the generated geometricalelectric model represent the results of the numerical simulation.

The numerical simulation is based on two different log curves, a curve recorded with a long-spaced tool and curve recorded with a short-spaced tool. A correlation log can also be provided, such as a self potential log or a gamma ray log, to confirm the layer sequence simulated by the software. It is also

possible to generate the true resistivity profile only based on the long-spaced measurements and on the stratigraphic log. The nominal well diameter should be assigned to correct the apparent resistivity values for well bore effects.

It was observed that the calculated mud resistivity values are not always consistent with the reported fluid property and, therefore, the interpretation results might be questionable since mud resistivity

determines the apparent resistivity correction for mud, mud cake and filtrate invasion. However, it is also possible that the reported mud resistivity is not reliable for the logged interval. Sensitivity analyses should therefore be run to evaluate more accurately the true mud resistivity.

Although the invasion diameter is calculated during the modeling process, it is not provided as a simulation result.

CASE HISTORY

Three wells were selected to apply the different methodologies for resistivity log interpretation. The wells are located in a sedimentary basin underlain by a folded and partially metamorphosed Paleozoic

basement. The depositional sequence is mainly made of shaly facies, but partly eroded carbonate and evaporitic sedimentary formations are also present. The carbonate sedimentary sequence originated from Jurassic to Quaternary and represents the most interesting gas bearing formation in the area. The reservoir net pay ranges from about 250 m to 100 m (in some marginal areas of the basin). Porosity

ranges between 13% and 20% and permeability is approximately 100 mD. The clastic carbonate

sequence is bounded by turbidites having porosity of 5 - 8 % and permeability between 0.1 and 5.0 mD. The well selection was based on the availability of a sufficient number of resistivity logs to apply the Russian interpretation approach, core analysis to validate porosity logs and to characterize fluids and rock quality, and well testing results to validate the calculated water saturation profiles. Furthermore, inconsistency had been found for all the selected wells between the water saturation values calculated as a function of true formation resistivity evaluated by the western conventional interpretation and the nature and quantity of produced fluids during well testing.

RESULTS AND DISCUSSION

The true formation resistivity values, Rt, obtained by application of the Russian interpretation are consistent with the apparent resistivity measured by long-spaced tools for layers thicker than 2 meters (fig 5). The stratigraphic sequence apparent from the resistivity values is not consistent with the

concavity changes of the response curve recorded by long-spaced tools due to low vertical resolution. The true formation resistivity profiles generated by numerical simulations are reliable when the synthetic and the real log are superimposed (fig 6). Generally, the superposition is very satisfactory except at the boundary of the analyzed interval where the Rt profile appears to be less reliable. Therefore, it is advisable that shoulder formations are also included when modeling the producing layer.

The comparison among simulations based on different tool combinations is shown in fig 7. In particular, the combination of the half meter- and eight meter-spaced lateral logs is the combination used for interpretation.

Fig 5:Resistivity values obtained by Russian interpretation

Fig 6:Resistivity profile generated by numerical simulation

The results obtained by application of the Russian manual methodology and by simulation were compared in terms of the true formation resistivity and invaded zone resistivity (fig 8). The resistivity values calculated with the Russian methodology are consistent to numerical simulations only when numerous reliable measurements are available, i.e., for layers approximately thicker than 2 meters. Numerical simulations seemed to be reliable for any layer thickness (fig 8 left). The layer subdivision adopted in the numerical simulations is greater than in the western or Russian interpretation because forward modeling attributes each concavity change to a formation anisotropy typical of a layer limit. However, measurement errors can influence the log response curve and induce concavity changes which are not due to the formation layering. A comparison between the invaded zone resistivity

calculated by the two interpretation methodologies indicated that results are in good agreement (fig 8 right).

The invasion diameter could only be calculated when the Russian methodology was applied. The results are reported in Tab 1.

Fig 7:Comparison of different resistivity profiles generated by numerical simulations

Fig 8:Formation and mud resistivity

The invasion diameter calculated for different layers of the same lithology are very consistent.

Furthermore, it is also reasonable to assume that the calculated invasion diameter is reliable when the formation resistivity and the invaded zone resistivity are reliable because Russian interpretation results are interdependent.

Tab. 1: Invasion diameter values Mud resistivity = 0.03 ?m Invasion diameter (m) 2.4 3.4 2.3 2.7 2.4 2.6 12 8 1 2 5 1.5

Layer thickness (m) The calculated invasion diameters are generally much greater than the typical values found for western wells. This is one of the reasons way interpretation based on laterolog measurements, like the western methodology, can not provide consistent results. In fact, the investigation depth of laterolog tools is smaller than the calculated invasion diameter and, therefore, the simulated resistivity profiles are not representative of the true formation resistivity.

The water saturation values are calculated on the basis of the true formation resistivity and porosity measurements. In the Russian countries the neutron-gamma tool, NGK, and the sonic tool, AK, provide the most reliable porosity measurements. In the case of the examined wells the porosity profile from the sonic tool were consistent with the porosity values measured on cores whereas the neutron-gamma tool overestimated the actual formation porosity (fig 9). This can be explained by considering that the neutron-gamma measurements are related to total formation porosity, while sonic measurements are related to the rock primary porosity only.

Fig 9:Porosity profiles from logs and porosity values from cores

Water saturation values were calculated using Archie’s law which is suitable for carbonate rocks in the absence of shales. Due to the lack of special core analyses standard values for the Archie’s law parameters in carbonate lithologies were assumed (a=1, m=2, n=2).

Comparison between water saturation values calculated as a function of porosity from neutron-gamma (fig. 10) and sonic measurements (fig. 11), respectively, show that consistent values are obtained on the basis of resistivity evaluated from modeling and Russian interpretation. Conversely, water saturation profiles obtained on the basis of resistivity evaluated by western interpretation did not prove reliable. Water saturation values calculated as a function of sonic porosity measurements seemed more

consistent with well testing with respect to saturation values calculated as a function of neutron-gamma porosity. In any case the application of Archie’s law requires reliable porosity measurements because it was verified that water saturation is affected more by uncertainties in porosity measurements than by formation resistivity. Furthermore, true formation resistivity squared profiles are not coherent with the adopted porosity curves. In fact, vertical resolution of resistivity and porosity measurements are not the same, and the calculated water saturation is often influenced by porosity variation even if the true formation resistivity does not change.

Finally, it was observed that the combination of the true formation resistivity evaluated with the western interpretation methodology and the porosity measurements from the neutron gamma ray tools lead to a water saturation profile which appeared locally consistent with well testing results. However, it must be emphasized that such agreement was purely casual, and due to a combination of errors (fig. 12).

Fig 10: Water saturation values as a function of porosity measured by neutron gamma tool.

Fig 11: Water saturation values as a function of porosity measured by sonic tool.

Fig 12: Comparison between different water saturation profiles.

Fig 12: Comparison between different water saturation profiles.

CONCLUSIONS

Results clearly showed that interpretation of the Russian resistivity logs according to the western methodology can not provide reliable true formation resistivity profiles, both due to the differences

existing between Russian and western tool configurations and to an unexpectedly deep mud invasion in the formation. Since the western interpretation approach is based on laterolog measurements the simulated resistivity profiles are not representative of the true formation resistivity because the instrument investigation depth is generally smaller than the calculated invasion diameters.

The resistivity values obtained by application of the Russian manual methodology and by numerical simulations are sufficiently consistent. The Russian methodology is very ingenious although extremely

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complex and very time consuming. The Rt-MOD software is very simple, only requires few data to run log interpretation, and quickly performs simulations.

The true formation resistivity values obtained with the Russian approach are reliable only for thick layers (more than 2 meter-thick) whereas results obtained from the software application are fairly consistent for any layer thickness. However, calculated mud resistivity values are not always consistent with the reported fluid property and when the simulated value differs significantly from the reported

measurement, the obtained interpretation results might be questionable. Although the layer sequence reproduced by the software may not be representative or the real formation, resistivity results seem to be consistent with the results obtained with the Russian interpretation.

Finally, it was verified that also porosity measurements can significantly affect water saturation and, therefore, the porosity curve to adopt for calculation of water saturation should be accurately selected. In fact, combination of erroneous true formation resistivity and porosity profiles might even lead to a locally consistent water saturation profile.

ACKNOWLEDGEMENTS

The authors are very grateful to Petroleum Software Technologies for providing access to the software

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RtMOD used in this research.

REFERENCES

Agip- Schlumberger, \, 1998.

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俄罗斯测井解释 F. Verga, P.P. Rossa，都灵理工大学；M. Piana, M. Gonfalini，

意大利埃尼集团石油总公司

2001年版权OMC

本文是在意大利拉文纳2001年3月28-30日海上地中海会议和展览。它是由OMC 2001计划委员会提交选定审查后的信息包含由作者提交的摘要。本文在介绍了OMC 2001没有被计划委员会审查。

摘要

石油或天然气储层的评价明显取决于电阻率的准确性以及数据和解释的可靠性。然而,作为西方的解释方法评价俄罗斯西方石油公司BKZ日志地层电阻率是非常麻烦的, 基于侧向测井解释,不适合俄罗斯解释特点和措施。名为RT模型记录的三个俄罗斯钻井电阻率测井资料，其中一个明显的发现是测试期间含水饱和度值和西方解释方法的性质和产生的流体速率不一致，并解释了俄罗斯的方法和应用软件，适用于俄罗斯的测井解释。俄罗斯方法需要手动对比实验电阻率测量和获得理论类型曲线地层电阻率、侵入带电阻率、侵入直径。RT

模型软件基于反演方法执行一个电阻率数值模拟用于生成地层和侵入带电阻率资料。

电阻率值的方法似乎是可靠的，且比在西方解释应用更符合测试结果。特别是俄罗斯的方法似乎是非常可靠的比两米厚层时,允许地层电阻率的评估和入侵直径也当深泥入侵。然而，俄罗斯的方法是复杂的和非常耗时的。从软件应用程序得到的结果是相当一致的任何层厚度。数值模拟是非常快的，简单的，只需要较少的数据运行的测井解释。然而，计算泥浆电阻率值并不总是与报道的流体性质一致。

介绍

由于最近的重大政治和经济变化发生在前苏联的一部分的国家,西方石油公司在这些领域扩大了他们的兴趣。然而，投资规划和油藏开发的战略需要有效的油气储量评价。西方石油公司必须依靠俄罗斯的工具和方法收集到的信息，然后使用不同的标准对油藏进行开发。事实上,俄罗斯国家和世界其他地区之间存在多样性,也因文化和语言障碍。同时有一种强烈的需要比较各自的经验和定义常见的方法。本研究旨在帮助定义一个可靠的过程来解释俄罗斯日志因为日志基本储层岩石物性的测定。特别是实现更准确的可能性解释俄罗斯电阻率的日志(BKZ日志),因为西方的方法,基于侧向测井仪的响应,未能提供可靠的结果,主要是由于俄罗斯和西方之间的差异的工具。事实上，计算含水饱和度剖面地层真电阻率的一个函数评价西方的解释,在试井的产液量和性质上不一致。

俄罗斯对电阻率测井解释方法的完全手册和基于实验电阻率点之间的比较和理论曲线标准,因此,它可以相当近似。一个新的开发软件是俄罗斯电阻的电阻率建模日志,从而允许一个完全自动的解释注册记录曲线。含水饱和度值计算作为一个真正的应用程序获得的电阻率值的函数不同的解释方法和不同的孔隙度测量的功能,目的定义是一个正确的解释过程,强调可能的误差源在储备评价解释俄罗斯日志。

俄罗斯的工具

对生产层的含水饱和度分布的确定是根据地层电阻率，也称地层真电阻率，这是由一系列的视电阻率解释估计的日志。事实上，这是直接测量地层真电阻率测井由于钻孔，泥浆的阻碍，和泥浆滤液侵入的影响。最小日志套件运行的大多数俄罗斯井通常包括电,卡尺,温度,和伽马射线设备,偶尔可以辅以中子伽马,密度、声波孔隙度测量。通常最小日志套件包含欧洲相应套件和仪表,除了遗漏一个显式的孔隙度工具,可与1985年以前美国陆上运行的相比。一般来说,日志数据呈现展品质量差和大多数日志硬拷贝黑色和白色的手工编辑。西方企业试图数字化俄罗斯日志,但有时在测试过程中结果是灾难性的,由于日志和深度范围内差异问题,以及缺乏一个系统日志质量控制,更不用说语言问题。此外,一些测井曲线通常结合在相同的情节,可以渲染生成的产品难以理解(哈里森,1995)。

在URSS地层真电阻率的评估, RT的评价，是基于测量记录横向器件。不同的横向测量(BKZ日志)相结合,使用不同电极间距从而调查不同深度远离井眼。典型的序列是由五或七种不同的工具以间距一半米八米不等。根据响应曲线短间距横向的工具限制识别和定位可靠的层真电阻率是评价的基础上获得长间隔横向响应曲线的工具。

横向分析复杂不对称反应显示测量曲线, 不允许一个视电阻率值评价非对称响应（即测得的值）的每个分析形成代表。因此,倒置的探测器(倒横向探头)经常运行与常规侧有相同的间距。当电阻率日志的套件包括相同间隔BKZ和倒BKZ曲线“伪补偿表示”梯度日志可以通过平均电导率读每个曲线(哈里森,1995)。

这个补偿曲线对称,深度识别和可用在感应等数字处理,集中和正常的日志。

正常获得的测量,集中和感应设备也用于地层电阻率评估,但只支持和验证结果的基础上,横向测量分析。事实上,感应测井的工具探测深度不允许日志的一致解释测量由于经常大量泥质入侵。

俄罗斯的解释

电阻率测井解释俄罗斯方法允许的地层真电阻率评价，侵入带电阻率，和侵入直径。它可以应用于记录数据没有任何初步的赔偿。可用不同的数量BKZ日志确定获得的电阻率值的可靠性。这个程序是完全手册，和电阻率数据校正和解释的重复，有时与实际测量的比较合适的迭代实现，无因次曲线。特别是，在解释程序使用的每一个电阻值必须是标准化与泥浆电阻率。然而,这不是一个标准的做法来测量泥浆电阻率。它从视电阻率测量结果记录在低孔隙率层评价泥浆电阻率是必要的。

需要初步校正方法来解决分层的视电阻率值影响,即影响存在相关邻层表现为不同的电特性研究层。每个电阻率值,测量在有限厚度的层上转换相应的电阻率值的理想无限层厚度(图1)。执行变换图形和要求的泥浆电阻率,工具间距L，地层厚度被称为H。

图1:视电阻率值转换到相应的理想值无限层厚度

理想的视电阻率值、通过法线,焦点、归纳,和横向测量工具的函数间隔L,所谓的解释的形式(图2)。

解释的形式再叠加理论型曲线，描述地层视电阻率 ,规范化的泥浆电阻率,测井间距L,井直径d。(图3)。每个无量纲曲线也具有给定值的归一化地层真电阻率。为了确定目的层的最佳匹配的报告解释形成真正的测量必须寻求曲线地层真电阻率。由于理论曲线进行了具体推导解释横向测量，聚焦，电感，和正常的测量需要比较不同的曲线，称为isoresistive曲线，并绘制在同一图表。该isoresistive曲线允许改造为重点，归纳，或正常测量等效侧测量具有相同直径的调查。

图3:叠加的真实数据无量纲理论曲线

提供了几个图表报告无因次标准曲线集类似于图3所示,每个特征是不同的泥浆侵入带电阻率和入侵的直径值。选择最合适的图表的帮助下使用另一个图表(图4)报告无量纲曲线的侵入带电阻率-设置-直径和入侵设置表单b .叠加的解释报告此图表上的视电阻率值提供了最可能的值侵入带电阻率和入侵直径。

图4：图为选择最合适的侵入带电阻率值和侵入直径。

视电阻率测量值的长间距横向工具薄层不具有代表性，因此，横向测量可用于解释过程中的数量是很有限的。因此，日志分析需要主观补充这种缺乏数据实现的解释，强烈影响的解释的可靠性。它不建议采用俄罗斯测井解释厚2米或更少的程序层。

数值解释

自动解释俄罗斯测井测量来确定地层真电阻率和侵入带电阻率可以通过使用Rt模型执行软件。

该软件生成的原理是二维几何的研究组和相应的合成视电阻率剖面正演模型，使用有限差分。该模型的校准，根据逆向建模过程，即模型的几何和电性能逐步修改直到达到合成和真实记录之间的令人满意的叠加。

正向和逆向建模的迭代重复，直到达到满意的收敛。电阻率值是分配给每一层的入侵和原始在生成geometricalelectric模型代表数值模拟的结果。

数值模拟是基于两个不同的测井曲线,曲线记录long-spaced工具和曲线记录短间距的工具。相关的日志也可以提供,如自我潜在的日志或伽马射线日志,确认的层序模拟软件。还可以生成真正的电阻率剖面仅基于long-spaced测量和地层日志。名义直径也应该分配给正确的井眼的视电阻率值的影响。

观察,计算泥浆电阻率值并不总是符合流体性质及报道,因此,解释结果可能有问题因为泥浆电阻率决定了视电阻率校正泥、泥饼和滤液侵入。然而,它也可能报告泥浆电阻率是不可靠记录的时间间隔。敏感性分析应该更准确地评估真正的泥浆电阻率运行。

虽然入侵直径的计算方法是在建模过程中，它不提供一个模拟的结果。 勘探史

三个井被选为电阻率测井解释应用不同的方法。油井位于一片底部沉积盆地褶皱和部分变质古生代基底。沉积序列主要是由泥质相,但部分碳酸盐和蒸发沉积地层也存在腐蚀。碳酸盐岩沉积序列来自侏罗纪第四纪,代表了最有趣的含气区内形成。水库的净范围约100米到250米不等(在一些边缘地区的盆地)。孔隙度范围在13%至20%之间,渗透率大约100 mD。碎屑碳酸序列是有界的浊积有5 - 8%的孔隙度和渗透率在0.1和5.0之间。选择是基于可用性的足够数量的电阻率日志应用俄罗斯解释方法,岩心分析孔隙度来验证日志和描述流体和岩石质量,以及测试结果来验证计算含水饱和度资料。此外,发现不一致的选择井含水饱和度值计算一个函数之间的西方传统的解释和地层真电阻率评估生产液体的性质和数量在试井。 结果与讨论

地层真电阻率值，RT，由俄罗斯解释中的应用得到了一致的视电阻率测量长间隔层厚度大于2米的工具（图5）。电阻率的地层序列明显价值观不相符的凹性变化的响应曲线记录long-spaced工具由于较低的垂直分辨率。地层真电阻率的概要文件生成的数值模拟是可靠的合成和真实的日志时叠加(图6)。一般来说，除了在叠加分析的时间间隔，RT分布似乎是不可靠的边界非常令人满意。因此，它是可取的，也包括建模时地层产层。

基于不同的工具组合模拟之间的比较是在图7所示。特别是在半米和八米的组合分隔开的横向日志是用于解释相结合。

图5:俄罗斯解释获得的电阻率值

图6:电阻率剖面生成的数值模拟

获得的结果由俄罗斯手册的应用方法和仿真比较的地层真电阻率、侵入带电阻率(图8)。俄罗斯的电阻率值计算方法是一致的数值模拟只有当大量可靠的测量,即层厚约2米。数值模拟似乎是可靠的任何层厚度(图8)。层细分采用数值模拟大于西部或俄罗斯解释因为每个凹度模型属性变化的典型地层各向异性层极限。然而,测量误差可以影响测井响应曲线和诱导凹度变化并非由于地层分层。对比侵入带电阻率计算的两种解释方法表明,结果很一致(图8)。 入侵直径只能当俄罗斯计算方法应用。结果报道在标签1。

图7:不同电阻率的比较概要文件生成的数值模拟

图8:地层泥浆电阻率

计算出的同一岩性不同层侵入直径一致。此外，它是合理的假设，当地层电阻率和侵入带电阻率可靠则计算出的侵入直径可靠，因为俄罗斯解释结果是相互依存的。

选项卡1:入侵直径值 泥浆电阻率= 0.03 Wm 层厚度(m) 入侵直径(米) 12 2.4 8 3.4 1 2.3 2 2.7 5 2.4 1.5 2.6 发现计算出的入侵直径一般比西方的典型值大得多。这是一个基于测井测量解释原因的方式，如不能提供一致结果的西方方法一样。事实上，双侧向测井工具的探测深度小于计算侵入直径和，因此,模拟电阻率资料并不代表地层真电阻率。

在含水饱和度的基础上计算地层真电阻率和孔隙度。在俄罗斯国家中子伽马工具、NGK和声波工具,正义与发展党,提供最可靠的孔隙度测量。的检查井的孔隙度剖面与孔隙度值测量声波测井仪是一致的核心而中子伽马工具高估了实际的地层孔隙度(图9)。这可以解释为考虑到中子伽马测量与地层孔隙度,而声波测量岩石原生孔隙度有关。

含水饱和度值是对地层真电阻率和孔隙度的测量计算。在俄罗斯国家中子伽马工具，该工具，和声波，AK，提供最可靠的孔隙度测量。在检查威尔斯从声波测井的孔隙度曲线与实测岩心而中子伽马工具高估了实际地层的孔隙率值一致的情况下（图9）。这可以通过考虑，中子伽马测量总地层孔隙度的相关解释，而声波测量相关的岩原生孔隙只有。

图9:孔隙度资料从日志和从岩心孔隙度值

含水饱和度值计算使用Archie定律适用于碳酸盐岩在缺乏页岩。由于缺乏特别的核心分析标准Archie定律在碳酸盐岩岩性参数的值被认为(m = 2 = 1,n = 2)。

比较水饱和度从中子伽马值计算孔隙度的函数(图10)和声波测量(图11),分别显示一致的价值观得到电阻率的基础上评估建模和俄罗斯的解释。相反,水饱和度资料得到电阻率的基础上评估由西方解释并不能证明可靠。含水饱和度值计算函数的声波孔隙度测量似乎更符合试井对饱和值计算中子伽马孔隙度的函数。在任何情况下Archie定律需要可靠的孔隙度测量的应用程序,因为它是验证孔隙水饱和度是影响的不确定性测量地层电阻率。此外,地层真电阻率的平方与采用概要文件不一致的孔隙度曲线。事实上,垂直分辨率电阻率和孔隙度的测量是不一样的,和计算含水饱和度往往是影响孔隙度变化不改变即使地层真电阻率。 最后发现的组合地层真电阻率与西方解释评价方法和中子伽马射线的孔隙度测量工具导致含水饱和度剖面出现在本地测试结果符合良好。然而,它必须强调,这样的协议是纯粹的休闲,而且由于错误的组合(图12)。

图10:含水饱和度值作为孔隙度测量的中子伽马函数工具。

图11:含水饱和度值作为声波孔隙度测量的工具函数。

图12:比较不同含水饱和度之间的配置文件。

结论

结果清楚地表明,俄罗斯电阻率解释日志根据西方方法不能提供可靠的地层真电阻率资料,同时由于俄罗斯和西方之间的差异现有工具配置和意外深泥形成的入侵。自西方的解释方法是基于侧向测井测量的模拟电阻率资料并不代表地层真电阻率,因为仪器探测深度一般小于入侵直径计算。

俄罗斯的电阻率值通过应用手册由数值模拟方法和充分一致。俄罗斯的方法是非常巧妙的虽然极其复杂和耗时。Rt-MOD软件非常简单,只需要一些数据来运行测井解释,并迅速执行模拟。

与俄罗斯的方法获得的地层真电阻率值是可靠的仅为厚层(超过2 meter-thick)而从软件应用程序获得的结果相当一致的任何层厚度。然而,计算泥浆电阻率值并不总是一致的报道时流体性质及模拟值的测量报告有很大区别,解释获得的结果可能会有问题。虽然层序列复制的软件可能不代表或真正的形成、电阻率的结果似乎与俄罗斯解释的结果一致。

最后,验证,也可以显著影响含水饱和度和孔隙度测量,因此,孔隙度曲线采用含水饱和度的计算应该准确地选择。事实上,错误的地层真电阻率和孔隙度资料甚至可能导致本地水饱和度剖面一致。 感谢

作者非常感谢石油软件技术提供软件RtMOD?用于这项研究。

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