页岩气的测井响应特征 翻译

2 页岩气的测井响应特征
2.1 页岩气的常规测井响应
页岩气的常规测井响应主要包括页岩储层的自然伽马、井径、声波时差、中子孔隙度、地层密度、岩性密度和深浅电阻率等。

吴庆红等（2011）研究认为斯伦贝谢公司于2004年开展了页岩气测井解释，建立了页岩气测井系列，包括自然伽马、补偿中子、补偿密度、电阻率、声波扫描、电阻率成像(FMI)、伽马能谱(HNGS)和元素俘获能谱测井(ECS)等，其中声波扫描、电阻率成像、元素俘获能谱测井是页岩测井的关键技术[10]。

潘仁芳（2009）研究总结了对页岩气储层有效的测井曲线及对应的响应关系[11]，见表3。

表3 页岩气测井曲线响应特征（文献[11]）
Tab.3 Response characteristics of shale gas well logging (data [11])
2.2 页岩气的常规测井系列
裸眼井测井常用三大测井系列、十一条测井曲线，可解决储层的岩性划分、物性评价和含油气性评价等。

由于页岩气测井的特殊性，需要对常规测井系列进行方法组合优选。

笔者认为，页岩气测井的主要内容应包括：岩性定性识别和定量评价、含气层的划分与评价、储集空间和渗流空间物性评价。

开展页岩气测井的关键问题是，那里是页岩层、源岩有机质含量如何、页岩含气性如何、裂缝等储渗空间发育程度怎样。

页岩气测井评价中，岩性定性识别和定量评价的常规测井方法主要包括自然电位测井、自然伽马测井和井径测井；含气层划分与评价的主要测井方法包括深浅侧向或深中感应电阻率测井、声波时差测井、密度测井和中子测井；储集空间和渗流空间物性评价的主要测井方法是声波时差测井、密度测井和中子测井。

值得指出，页岩气常规测井系列从方法上似乎涵盖了现代测井全部方法，但页岩气测井方法组合和资料解释的侧重点却与石油测井有所不同。

这与页岩气本身的特殊性密切相关。

测井新技术中的核磁双Tw测井，进行差谱分析后,可根据差谱识别油、气、水层,对双TE测井进行移谱分析,可以判断气层。

时间推移测井,下套管后最佳时间测量的中子与固井后24h内测量的中子曲线重叠,利用其差值可以评价气层[2]。

2 Logging Response Characteristics of Shale Gas
2.1 Conventional Logging Response of Shale Gas
Conventional logging responses of shale gas mainly include natural gamma ray, well diameter, acoustic time, neutron porosity, formation density, lithology density and depth resistivity of shale reservoir. On the basis of the research in 2011, Wu Qinghong, etc think that Schlumberger Company has carried out the logging data interpretation of shale gas and has established logging suite of shale gas in 2004. This logging suite includes natural gamma ray, compensation neutrons, compensation density, resistivity, sound waves scanning, resistivity imaging (FMI), gamma ray spectrum (HNGS) and element captured spectrometry logging (ECS) and so on. And among these, the key technologies of shale logging are sound waves scanning, resistivity imaging and element captured spectrometry logging [10]. In 2009, Pan Renfang has summarized the logging curves that are effective to shale gas reservoir and their corresponding relationships as shown in Table 3.
2.2 Conventional Logging Suite of Scale Gas
Openhole logging usually uses three logging suites including eleven logging curves to solve the problem of lithology division, physical parameters evaluation and oiliness evaluation of the reservoir. Because of the particularity of shale gas logging, conventional log series need to be choosed and combined renewedly.
In the author’s opinion, the main content of shale gas logging should include the qualitative identification and quantitative evaluation of the lithology, the classification and evaluation of the aerationzone and the physical parameters evaluation of the reservoir space and seepage space. The important problems of scale gas logging are the situation of shale strata, organic matter content of source rock, gas content of shale and permeability space abundance of reservoir. In shale gas logging evaluation, the conventional logging methods of the qualitative identification and quantitative evaluation of the lithology mainly include natural potential logging, natural gamma ray logging and well diameter logging; the conventional logging methods of the classification and evaluation of aeration zone are mainly include depth lateral logging or depth-mid induction resistivity logging, acoustic time logging, density logging and neutron log; the conventional logging methods of physical parameters evaluation of reservoir space and seepage space mainly
include acoustic time logging, density logging and neutron log.
It' is worth pointing out that shale gas conventional logging series seems to cover all modern logging methods, but the emphasis of the combinatorial methods and data interpretation of shale gas logging is quite different from oil well logging. This is related with the special density of the shale gas itself.
MRI double Tw logging is one logging method of of new logging technology. The steps of this logging method are as follow: First, the differential spectrum should be anal sized. Second, according to the differential spectrum, oil,.wanter and gas should be distinguished. Third, the shifted spectrum analysis to the double TE logging should be done. Then, the air layer can be identified.Time lapse logging is that air layer is evaluated by the D-value of data of the neutron measured at the best time after running casing and the neutron measured within 24 hours after cementing[2].
Tab.3 Response characteristics of shale gas well logging (data [11])
3.3 页岩气的测井评价技术展望
3.3 The Outlook of Scale Gas Well Logging Evaluation Technology
由于页岩气自身的特殊性，能够用于页岩气评价的测井资料往往受到多种因素控制，直接采用单一测井信息或某一储层参数进行页岩气评价解释研究，除了在一些特殊情况下可以取得满意效果外，一般很难推广使用。

当前的最佳选择是基于地质、岩心、测井和生产动态资料开展四性关系研究，建立有关页岩气评价地质参数解释模型，以利用测井资料进行页岩气评价。

由于页岩气储层参数与多种测井信息之间的定量关系往往难以确定，因此，可借用现代数学中的灰色关联判别技术和神经网络技术进行页岩气的精细分析和预测评价，借用R/S 变尺度分析技术开展页岩气层裂缝识别与评价。

这些技术方法的优点是勿需考虑具体的数学模型，“隐含式”可表达出页岩气储层参数与测井响应之间的非线性关系，从而实现页岩气储层的定量分析[22,23]。

另外，将新的测井技术（比如核磁共振测井、阵列感应测井等）以及精细二维及三维地质勘探解释技术[8]引入到页岩气综合评价中，多角度、多方位地收集页岩气储层的相关信息，从而提高页岩气层的测井综合评价精度。

3.3 The Outlook of Scale Gas Well Logging Evaluation Technology
For the particularity of shale gas itself, logging data that can be used to evaluate shale gas is controlled by various factors. Except getting some satisfied results the special circumstances, direct using single logging data or a certain reservoir parameters to evaluate, interpret shale gas is generally difficult to widely use. At present, the best option is based on geology, core, well logging and production dynamic data, carrying out the study of “the relation of the four characters”, building shale gas evaluation model, and the using logging data to evaluate shale gas.
Because it is always difficult to make sure the quantificational relationship between shale gas reservoir parameters and various logging data, shale gas can be subtly analyzed and evaluated by grey correlation discriminant technology and neural network technology in contemporary mathematics, and shale gas stratum crack and shale gas stratum crack can be identified and evaluated by R/S analysis technology of variable scale. The advantages of these techniques are that specific mathematical model is not required to considered, and the nonlinear relationship between shale gas reservoir parameters and the response of well logging. The quantificational analysis of shale gas reservoir can be realized [22, 23].
In addition, introducing new logging technology (such as nuclear magnetic resonance logging, array induction logging, etc), subtle 2D and 3D geological exploration interpretation technology into shale gas comprehensive evaluation, as well as collecting the correlative data of shale gas
reservoir from multi-angles, thereby, can improve the comprehensive evaluation precision of shale gas well logging.
3.2
页岩本身具有很低的渗透率，但网状裂缝系统大大提高了页岩的储气能力，因此，在对页岩气藏进行储量计算时，对页岩中裂缝系统的评价十分重要。

目前，常用测井方法评价裂缝，如微电阻率测井、声波测井、双侧向测井、成像测井等[20，21]。

声波测井对低角度和水平裂缝反映较好、对高角度裂缝反映较差。

双侧向测井是近年发展起来的识别裂缝的好方法，裂缝越发育，双侧向电阻率越低；垂直及网状裂缝越发育双侧向差异越大。

高角度裂缝的有效性表现为电阻率曲线在高阻背景上有所下降，深浅侧向电阻率幅度差很大，但是如果差异过大，裂缝的张开度虽很大，但横向延伸很短，裂缝的有效性就很差；低角度裂缝的有效性表现在电阻率曲线在高阻背景上的明显降低，曲线形状尖锐，一般呈负差异，说明横向延伸较远，幅度差越大，张开角度就越大，有效性就越好；如果出现正差异，说明横向延伸短，有效性就差。

此外，应用于页岩裂缝识别的还有井径曲线的变化、异常流体压力和应力的关系、相干分析技术等[16]。

Shale itself possesses very low permeability. However, the system of network fractures greatly improves the gas storing capacity of shale. Therefore, when the reserves of shale gas reservoir are calculated, the evaluation of shale crack system is very important.
At present, frequently-used well logging methods are micro resistivity logging, acoustic logging, dual laterolog, imaging lagging, and so on. Acoustic logging can reflect low-angle and horizontal crack well, and can not reflect high-angle crack well. Dual laterolog, which develops in recently years, is the best way to identify crack, the more developmental crack, the lower dual lateral electric resistance rate; and the more developmental vertical and meshy crack, the bigger difference of dual laterlog. The effectiveness of high-angle crack shows that the resistivity curve will decline under the background of high electric resistance and the magnitude difference of depth- shallow lateral electric resistivity rate is very wide. However, if the difference is overlarge, the opening of crack is wide, but the horizontal expansion is very short. So the effectiveness of crack is quite bad. The effectiveness of low-angle crack shows that the resistivity curve will decline obviously under the background of high electric resistance, and the curve shape is sharp and generally shows negative difference. This indicates hat the further horizontal extension, the greater magnitude difference and the wider opening angle can lead the better effectiveness. If the positive difference appears, then the horizontal extension is short, and so the effectiveness is bad.Besides, the hole diameter curve change, the relation between abnormal fluid pressure and
stress and coherence analysis technology also can be applied to the identification of shale crack.。