不同煤体结构的高阶煤储层物性特征及煤层气产出机理

发布时间：2018-05-06 17:35

本文选题：高阶煤 + 煤体结构　；参考：《中国科学:地球科学》2017年01期

【摘要】：煤储层物性是影响煤层气解吸、扩散、渗流的关键因素,其好坏直接决定煤层气井的产气效果.本文以高阶煤为例,基于压汞、低温液氮吸附、等温吸附、煤粒甲烷放散初速度测试以及煤层气井现场自然解吸数据,系统探讨了构造破坏作用下高阶煤的孔隙性、吸附性、扩散性、渗透性等物性的响应规律,建立了不同煤体结构高阶煤储层几何模型、扩散模式图及气体产出综合模式图.研究认为,高阶煤经历构造作用后孔隙性得到改造,不同孔径段孔隙数量均有所增加,中、大孔增加最为明显,孔隙连通性发生差异性变化,这种孔隙性的变化是造成不同煤体结构煤的吸附/解吸性、扩散性等储层物性出现差异的根本所在.原生结构和碎裂结构煤基质孔隙以微孔为主,相对缺少大孔以及大孔连通性较差的孔隙特征,制约着初期气体的解吸和扩散,而较小孔径段孔隙连通性相对较好利于后期气体的解吸和扩散,更由于气体解吸衰减速度慢,易形成长期的产能;碎粒结构和糜棱结构煤吸附、解吸能力增强,自然条件下气体扩散能力强,但储层条件下渗透率的强应力敏感性,导致该类储层渗透性最差,渗流能力弱制约了扩散和解吸的发生;气体综合产出过程中,不同煤体结构的煤储层随着储层压力的变化基质孔隙气体扩散模式发生动态演化,过渡型扩散不断增强,Fick扩散不断弱化,气体的扩散能力不断降低,其中微孔和过渡孔是限制气体扩散的主要孔径因素;提出的储层条件下气体产出的综合模式图可以显示制约不同煤体结构煤储层气体产出的关键因素所在,有助于对储层进行针对性改造.
[Abstract]:The physical properties of coal reservoir are the key factors affecting the desorption, diffusion and percolation of coalbed methane (CBM), which directly determine the gas production effect of CBM wells. Taking high-order coal as an example, based on mercury injection, low temperature liquid nitrogen adsorption, isothermal adsorption, initial velocity measurement of methane release from coal particles and field natural desorption data of coalbed methane wells, the porosity and adsorption of high-order coal under tectonic failure are systematically discussed. Based on the response laws of physical properties such as diffusivity and permeability, the geometric model, diffusion model diagram and gas production model diagram of high-order coal reservoirs with different coal body structures are established. The study shows that the porosity of high-order coal is reformed after structural action, and the number of pores in different pore sections is increased, and the increase of large pores is the most obvious, and the difference of pore connectivity occurs. The change of porosity is the root of the difference in the physical properties of different coal bodies, such as adsorption / desorption, diffusion and so on. The pores of primary and fractured coal matrix are mainly micropores, which are relatively short of large pores and poor connectivity of macropores, which restrict the desorption and diffusion of gas in the initial stage. The pore connectivity of smaller pore segments is more favorable to the desorption and diffusion of gas in the later stage, and because of the slow rate of gas desorption and attenuation, it is easy to form long-term productivity, and the desorption ability of granular structure and chyloidal structure coal adsorption is enhanced. Gas diffusion ability is strong under natural condition, but permeability is sensitive to stress under reservoir condition, which leads to the worst permeability of this kind of reservoir, and the weak seepage ability restricts the occurrence of diffusion and desorption. With the change of reservoir pressure, the diffusion model of matrix pore gas in coal reservoirs with different coal structure evolves dynamically, the transient diffusion becomes stronger and Fick diffusion becomes weaker, and the diffusion ability of gas decreases. Among them, micropore and transition pore are the main pore size factors limiting gas diffusion, and the comprehensive model diagram of gas production under reservoir conditions can show the key factors that restrict the gas production of coal reservoirs with different coal structures. It is helpful to reform the reservoir.
【作者单位】：河南理工大学能源科学与工程学院;中原经济区煤层气(页岩气)协同创新中心;

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