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川西地区火山碎屑熔岩气层低阻成因浅析
Genesis of low resistivity in pyroclastic lava gas reservoirs, western Sichuan Basin
吴煜宇1 李 亚1 赖 强1 谢 冰1 殷 榕1 李 庚2
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作者单位:1. 中国石油西南油气田公司勘探开发研究院 2. 中国石油川庆钻探工程有限公司地质勘探开发研究院
中文关键字:川西地区 火山碎屑熔岩 低阻成因 微孔隙 蚀变 高束缚水饱和度
英文关键字:Western Sichuan Basin; Pyroclastic lava; Low-resistivity genesis; Micropore; Alteration; High irreducible-water saturation
中文摘要:    为明确四川盆地西部二叠系峨眉山组基性火山碎屑熔岩气层低阻成因,综合利用岩心孔渗、XRD 衍射、CT 扫描、恒速压汞、扫描电镜和相渗等岩石物理实验,结合地质与测井资料,对川西火山岩气层低阻成因进行研究。结果表明:①火山岩相控制着火山岩岩性,喷溢相火山碎屑熔岩成岩时与围岩温差大,冷凝速度快,矿物结晶程度低,玻璃质含量高,为后期脱玻化微孔隙发育和矿物蚀变奠定了基础,因此,火山岩相是低阻气层的宏观主控因素;②微观上,川西火山碎屑熔岩脱玻化形成大量微小孔隙,且连片发育,易吸附地层水形成良好的导电通路导致地层电阻率降低,同时,脱玻化孔的形成加剧了火山岩的蚀变程度,蚀变后的绿泥石以“孔隙内衬式”附着在孔隙壁上形成比较连续的“黏土壳”,经吸附大量地层水进一步导致地层束缚水含量增高,增强了地层的导电能力,地层电阻率进一步降低,因此,脱玻化形成的大量微孔隙和高度蚀变形成的绿泥石“黏土壳”的双重叠加作用造成的高束缚水饱和度是川西火山碎屑熔岩气层低阻的微观主控因素。
英文摘要:    In order to figure out some genesis of low resistivity in basic pyroclastic lava gas reservoirs of the Permian Emeishan Formation, western Sichuan Basin, the low-resistivity genesis was studied by making comprehensive use of petrophysical experiments (such as core porosity and permeability, X-ray diffraction, CT scanning, constant-rate mercury injection, scanning electron microscope, and relative permeability) and geological and well-logging data. Results show that (1) for volcanic rocks, facies controls lithology. During diagenesis of eruptive-facies pyroclastic lava, its temperature was more different from its surrounding rock, leading to fast condensation, low mineral crystallization, and rich vitreous content, which might lay foundation for the development of vitrified micropores and the mineral alteration in later stage, also indicating that the volcanic facies is one macroscopic factor controlling low-resistivity gas reservoirs; and (2) microscopically, the pyroclastic lava was devitrified to form a large number of developed and massive micropores, resulting that it was easy to absorb formation water to form better conductive path, further reduce resistivity. At the same time, those formed devitrified micropores might intensify volcanic alteration. The altered chlorite was adhered to some micropore walls in the form of “pore liner” to form relatively continuous “clay shell”, which could absorb large amount of formation water so as to further increase irreducible-water content, enhance conductivity, and further decrease resistivity. Thus, both high irreducible-water saturation caused by the superposition of abundant devitrified micropores and highly altered chlorite “clay shell” should be microscopic factors affecting low resistivity in the pyroclastic lava gas reservoirs, western Sichuan Basin.
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国内统一连续出版物号:CN51-1159/TE |国内发行代码: |国际标准出版物号:ISSN1673-3177 |国际发行代码:
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