| 连续型致密砂岩气近源累计聚集的特征及成因机制 |
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| 引用本文： | 郭迎春,宋岩,庞雄奇,姜振学,付金华,杜建军.连续型致密砂岩气近源累计聚集的特征及成因机制[J].地球科学,2016,41(3):433-440. |
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| 作者姓名： | 郭迎春 宋岩 庞雄奇 姜振学 付金华 杜建军 |
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| 作者单位： | 1.中国地质科学院地质力学研究所，北京 100081 |
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| 基金项目： | 中国博士后科学基金2014M550984中国地质调查局地质大调查项目12120115003501国家自然科学基金项目U1262205 |
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| 摘 要： | 致密砂岩气是非常规油气资源的重要组成部分，是当前技术条件下可动用程度最高的部分.致密砂岩气可分为连续型致密砂岩气和圈闭型致密砂岩气.通过系统地对比圈闭型和连续型致密砂岩气在运聚、分布上的地质、地化特征差异，并使用物理模拟实验揭示了连续型致密砂岩气呈近源累计聚集的动力学成因机制.研究表明:圈闭型致密砂岩气是天然气远距离运聚的结果，在天然气组分和碳同位素上都有很明显的分馏效应，具有良好的输导体系，形成了“常规圈闭汇聚、具有边底水、优质盖层封盖”的特征；连续型致密砂岩气是近源累计聚集的结果，天然气组分和碳同位素基本不产生分馏效应，同一地区碳同位素呈现离散性，表现出“连续分布、近源汇聚、气-水分布复杂或倒置”的特征.连续型致密砂岩气近源累计聚集是致密砂岩储层中近纳米级孔喉背景下天然气运移动阻力变化及平衡的结果.在天然气运移至气-水临界界面之前，气-水界面将天然气与地层水分为两个系统，天然气运移的动力是气体异常压力，浮力作用产生的基本条件不满足，运移阻力是上覆地层水压力和毛细管压力.连续型致密砂岩气圈闭可认为是非常规动力圈闭，其核心可概括为“(近)纳米级孔喉、气体活塞式推进、浮力基本不起作用、动阻力平衡决定气-水界面”.
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| 关 键 词： | 致密砂岩气 近源聚集 连续型 圈闭型 石油地质 |
| 收稿时间： | 2015-06-25 |
Characteristics and Genetic Mechanism of Near-Source Accumulated Accumulation for Continuous-Type Tight-Sand Gas |
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| Abstract: | Among the unconventional gas supply sources, tight-sand gas constitutes a significant percentage, which is the most available part under current technology. It can be divided into two types, continuous-type and trap-type. Geological and geochemical differences in characteristics on migration, accumulation, and distribution between trap-type and continuous-type tight-sand gas were compared systematically. Through physical simulation experiments, the dynamic genetic mechanism of near-source accumulation of continuous-type tight-sand gas was revealed. Trap-type tight-sand gas is the result of natural gas accumulation for a long migration distance with a good conducting system, causing an obvious fractionation on gas composition and carbon isotope and resulting in the following characteristics-"convergence in conventional traps, with edge and bottom water, high-quality sealing". Continuous-type tight-sand gas is the result of near-source cumulative accumulation. Consequently, the gas composition and carbon isotope fractionation effect is unconspicuous, and discreteness exists among carbon isotopes in the same area. Different from trap-type, the continuous-type tight-sand gas exhibits the following characteristics such as "continuous distribution, near-source aggregation, complex or inverted gas / water distribution". The near-source accumulation of continuous-type tight-sand gas is consequence of counterbalance between force and resistance when gas migrates in nanoscale pore-throats developed in tight sandstone reservoirs. Before the natural gas migrates to the critical gas-water interface, it is separated into gas system and water system by the inversed gas-water interface. The gas migration force is abnormal gas pressure, while the need to generate buoyancy cannot be met. The gas migration resistances include overburden formation water pressure and capillary pressure. The magic trap of continuous-type tight-sand gas can be considered unconventional dynamic trap which core contents can be summarized as "(almost) nanoscale pore-throat, gas migrate follows the piston principle, buoyancy does not work, balance between force and resistance determines gas-water interface". |
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