页岩气储层含气量计算方法研究及测井应用

发布时间：2018-08-27 16:15

【摘要】：北美页岩气的成功开发,第三次能源革命就此兴起。中国作为一个页岩气储量大国,在页岩气勘探开发方面得到了高度重视,并且已经取得了阶段性成果。页岩气在储层中的储集方式有三种,游离态,吸附态和溶解态。其中溶解态天然气能够在一定情况下向吸附态方向转化,含量相对较低,因此页岩气主要由游离气和吸附气两种赋存状态为主。在勘探开发过程中,页岩气的含气量一直是评价储层储量的关键点。其中的游离气含气量评价主要借鉴常规砂岩已有的评价方法;吸附气主要利用吸附模型评价吸附气含气量,且种类较多。例如Langmuir单分子层吸附模型、BET多分子层吸附模型、微孔充填模型、DA-Langmuir等温吸附模型和基于Langmuir单分子层吸附模型的改进模型等等。本文首先简要介绍了页岩气储层的基本特征和页岩储集空间特征。阐述了页岩复杂而相对特殊的储集空间。进而通过一系列岩石物理实验考察并深入分析了此种特殊储集空间对物性的影响。简述了基于等温吸附曲线的页岩孔隙微观表征方法,比较各个方法的优劣,认为H-K、DA和QSDFT方法较为适合页岩孔隙表征。测量了5块龙马溪组页岩岩电与核磁T2谱,发现T2谱基本属于双峰或三峰分布,前峰明显高于后峰。主峰均在1ms以下,充分反映了页岩特殊的微孔隙空间;后两个峰一般在15ms和130ms左右,分别反映页岩孔隙中的中孔和黏土层间微裂隙。进而在核磁T2谱的基础上提出了一种简化页岩孔隙模型,将页岩孔隙空间分为两部分,一部分为孔径在6nm以下,具有较强吸附能力的微孔隙,一部分为大于6nm且天然气主要以游离气为主的孔隙。在游离气含气量计算的精度方面主要依赖含水饱和度的计算,本文主要选用阿尔奇公式评价含水饱和度,并对其适用性进行了探讨和验证。分析数据时,发现n值与样品比表面和孔容存在正相关关系,与孔径存在负相关关系,m值与样品比表面和孔容存在正相关关系,并且层理方向影响饱和度指数n值的测量,竖直层理的样品的n值更小;而对于水平层理样品的n值较大且更为可靠。简述了吸附气基本特征和目前现有的吸附模型,利用核磁T2谱与孔径分布进行比较,进而得到横向弛豫时间与孔径分布之间的函数关系。将现有的固液气三相等温吸附模型进行改进,引入过剩吸附量概念,使之更为符合实际地层情况。对模型各个参数求取方法进行了探究,以确定模型参数。最终将上述方法应用到实际井中,并与岩心含气量数据进行对比,取得了较为满意的效果。
[Abstract]:The successful development of shale gas in North America led to the third energy revolution. As a large country of shale gas reserves, China has received great attention in shale gas exploration and development, and has achieved some achievements. There are three types of shale gas in the reservoir: free state, adsorption state and dissolved state. The dissolved natural gas can be transformed to the adsorptive state under certain conditions, and the content is relatively low. Therefore, shale gas mainly consists of free gas and adsorption gas. In the process of exploration and development, shale gas content is always the key point to evaluate reservoir reserves. The evaluation of free gas content mainly refers to the existing evaluation methods of conventional sandstone, and adsorption gas mainly uses adsorption model to evaluate the gas content of adsorbed gas, and there are many kinds of adsorbed gas. Such as Langmuir monolayer adsorption model, micropore filling model, DA-Langmuir isothermal adsorption model and modified Langmuir monolayer adsorption model, etc. In this paper, the basic characteristics of shale gas reservoir and the characteristics of shale reservoir space are introduced briefly. The complex and relatively special reservoir space of shale is expounded. Furthermore, through a series of rock physics experiments, the influence of this special reservoir space on physical properties is investigated and analyzed in depth. The microcosmic characterization methods of shale pores based on isothermal adsorption curves are briefly described. The results show that H-KnDA and QSDFT methods are more suitable for characterization of shale pores. The T 2 spectra of 5 blocks of Longmaxi formation shale rock are measured. It is found that the T 2 spectrum basically belongs to two peaks or three peaks, and the front peak is obviously higher than the back peak. The main peaks are below 1ms, which fully reflect the special micropore space of shale, and the latter two peaks are generally about 15ms and 130ms, which reflect the mesoporous and interlayer microfractures in shale pores, respectively. On the basis of T2 spectrum of NMR, a simplified pore model of shale is proposed. The pore space of shale is divided into two parts, one is micropore with pore size below 6nm, which has strong adsorption ability. Part of the pore is larger than 6nm and the natural gas is mainly free gas. The accuracy of free gas volume calculation mainly depends on the calculation of water saturation. In this paper, Archie formula is used to evaluate water saturation, and its applicability is discussed and verified. When analyzing the data, it is found that there is a positive correlation between n value and the specific surface and pore volume of the sample, a negative correlation between n value and pore size, and a positive correlation between the m value and the specific surface and pore volume of the sample, and the stratification direction affects the measurement of saturation exponent n. The n value of vertical bedding samples is smaller than that of horizontal bedding samples, and the n value of horizontal bedding samples is larger and more reliable. In this paper, the basic characteristics of adsorption gas and the existing adsorption models are briefly described. The T _ 2 spectrum of NMR is compared with the pore size distribution, and the functional relationship between transverse relaxation time and pore size distribution is obtained. The existing solid-liquid gas three-phase isothermal adsorption model is improved and the concept of excess adsorption capacity is introduced to make it more in line with the actual formation conditions. In order to determine the parameters of the model, the method of obtaining each parameter of the model is explored. Finally, the method is applied to practical wells, and compared with core gas content data, satisfactory results are obtained.
【学位授予单位】：吉林大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P618.13;P631.81

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