层状盐岩能源储库典型夹层渗透特性及其密闭性能研究

 夹层的渗透率是深部层状盐岩中能源储库密闭性评价的关键参数。针对我国深部层状盐岩中常见的3种典型夹层，采用稳态气测法测试了渗透率并给出密闭性分析结果。研究指出：(1) 3类典型夹层的低渗特征明显，渗透率均为10－2～10－5 mD；但各盐矿区的夹层岩性及地质条件差别较大，导致渗透率出现较明显差异，其中以平顶山硬石膏泥岩的渗透率最低、渗透率变化范围居中；金坛灰质泥岩渗透率次之、变化范围却最大；而淮安含盐泥岩渗透率最高、变化范围最小。(2) 静水压力对渗透率的影响极为显著，具体表现为静水压力越大渗透率越低；存在某一“压密临界压力”，当静水压力位于该值前渗透率随静水压力增大而急剧下降(下降1～2个数量级)，超过该值后渗透率降低很小并渐趋于平缓；静水压力与渗透率基本满足 (K为渗透率；P为静水压力；A，B为拟合参数)的拟合关系。(3) 渗透率随静水压力变化的内在机制是测试岩心具有可压缩性，但压缩效果随压力增大逐渐减小，到一定程度后增加压力也无法使岩体进一步压密，从而导致渗透率渐趋于恒定。以上研究表明，中国层状盐岩的典型夹层均具有较低的渗透率，可基本满足能源储库的密闭性要求。

INVESTIGATION ON PERMEABLE CHARACTERISTICS AND TIGHTNESS EVALUATION OF TYPICAL INTERLAYERS OF ENERGY STORAGE CAVERNS IN BEDDED SALT ROCK FORMATIONS

The permeability of interlayer is a key parameter for the tightness evaluation of energy storage caverns constructed in bedded rock salt formations. Thus，the steady gas flow method of permeability tests for typical interlayers of 3 kinds of bedded rock salt areas of China，as well as the analysis of tightness evaluation，has been carried out. The research indicated that：(1) The low permeable properties of the three kinds of typical interlayers are very obvious，with the corresponding permeability range of 10－2–10－5 mD. Due to the large difference of petrophysical properties and geological conditions of interlayers in different areas，the permeability exhibits obviously different with each other，in which the anhydrite mudstone of Pingdingshan has the lowest permeability，but the variance range is the medium；the calcareous mudstone of Jintan has the middle permeability，but the variance range is the maximum；and the saline mudstone of Huai?an has the highest permeability，but the variance range is the minority. (2) The hydrostatic stress states greatly influence the permeability，exhibiting the permeability decreasing as hydrostatic stress increasing. The“compaction criticle pressure”phenomenon is obviously for permeability. When the hydrostatic stress is lower than the transition stress，permeability decreases rapidly(about 1–2 orders). However，while beyond the transition stress the permeability decreases very slow and sustains steady gradually. The fitting relationship of hydrostatic stress versus permeability can be basically expressed by power function： (K is permeability，P is hydrostatic pressure，A and B are fitting parameters). (3) The mechanism of the permeability?s development versus the hydrostatic stress informs that the compressibility of porous interlayer rock. But the compaction effect will become lower and lower even become almost useless while the hydrostatic stress has reached some threshold value；so the permeability will not decrease after then. The test results presents that the permeability of the typical interlayers in bedded salt rock in China is very low so the tightness of storage caverns is basically satisfied.