陆相盆地低煤级煤储层特征研究——以准噶尔、吐哈盆地为例

Features of Low Rank Coal Reservoir in Limnic Basins

研究了准噶尔、吐哈盆地低煤级煤储层的特征 ,结果表明 :该储层几何形态复杂 ,且受成煤环境的控制 ,表现出显著的规律性变化 .煤体形态可归纳为与成煤环境对应的 4种类型 ,其中形成于湖成三角洲的朵状、舌状煤体成藏规模最大 .浅部煤储层以含气量低、甲烷浓度低、含气饱和度中等、含气强度大为特征 ;但在构造相对简单的盆缘斜坡深部具有很好的勘探开发潜力 .煤储层孔容及比表面积都很大且变化范围也大 ;中值孔径、孔隙率的变化特征与孔容一致 ,预示了低煤级煤储层较高的基岩渗透率 .兰氏体积和兰氏压力都显著低于中、高煤级煤储层 ,煤储层达到饱和的机率更大 ,更容易解吸 .古构造应力场控制着煤储层割理裂隙系统的发育程度和分布规律 ,现代构造应力场特征影响煤储层割理裂隙系统的开合程度 ,盆缘斜坡多为高渗区 .

The low rank coal reservoirs in limnic basins of Jungaar and Tuha were researched. The result shows that the geometric pattern of the reservoir is complex and controlled by the coal forming environment, displaying a regular variation. The geometric patterns can be divided into four types, each of which corresponding to a kind of coal forming environments; Among them the lobate and ligulate coal bodies are the favorable ones for forming gas pools in the largest scale. The shallow coal reservoirs are characterized by low gas content, low methane density, medium gas saturation and gas bearing intensity. While at the deep levels of the basin margin slopes with relevant simple structure, the reservoir has some potential in development and exploration of the gas. The specific pore volume and the specific surface area are larger and with a wider variation in contrast with medium and high rank coal reservoirs. The variation of medium pore diameter and porosity factor is in accordance with that of the pore volume, showing a high permeability of low rank coal reservoirs. Both Langmuir volume and Langmuir pressure of the reservoir are obviously lower than that of medium and high rank coal reservoirs, showing that the reservoir has a high probability to be saturated and desorbed. The paleo structural stress field controls the development and distribution of cleat and fracture systems,while the modern field affects the opening and closing of them.