层状盐岩储库长期运行腔体围岩流变破坏及渗透现象研究

Investigation on rheodestruction and permeability of surrounding rock for long-term running storage cavern in bedded rock salt

通过热力耦合作用下层状盐岩流变实验研究可知,层状盐岩内部各层之间由于蠕变率不同变形不协调,导致层状盐岩体内多重剪切破坏,层间流变破坏后呈网格状,孔隙、裂隙增多,渗透率比未扰动时提高5个数量级,储库长期运行腔体围岩流变破坏后天然气必然发生泄漏。同时,层状盐岩流变破坏后气体渗透实验表明,其渗透率与有效体积应力关系为K=16.5×10-15 exp(-0.035Θe)。基于裂隙介质,建立了层状盐岩储库长期运行腔体围岩流变破坏后渗透特性数学模型,并对金坛天然气储库长期运行腔体围岩渗透特性进行了数值模拟,结果表明:由流变破坏造成的盐岩与夹层交接面处产生的裂隙是气体渗透的主通道,具有较强的导气能力,夹层内部气体渗透滞后于层间裂隙气压,渗透速度随时间的延长逐渐减小,最后达到稳定状态。所以,高盐分泥岩夹层对天然气储库长期运行腔体围岩的渗透特性具有很大影响,确定合理的运行压力是保证天然气储库不发生渗漏的必要条件,为我国盐岩溶腔储库长期运行腔体围岩天然气渗漏现象研究提供一些参考依据。

According to study on coupled thermo-mechanical creep properties of bedded rock salt,it is shown that the deformation within bedded rock salt is out of line;it leads to multiple shearing destruction and becoming grid between the interlayer of bedded rock salt;meanwhile,the pores and fissures are increased;the gas permeability is augmented and it raised 5 orders of magnitude than not disturbance;so natural gas must leak when gas storage cavern under long-term running.The experimental study of gas permeability of bedded rock salt at rheodestruction shows that the relation between gas permeability and effective volume stress is K=16.5×10-15 exp(-0.03Θe).A mathematical model for long-term running permeability of gas storage cavern in bedded rock salt is established;and the numerical simulation for Jintan Gas Storage Cavern is carried out;the results are as follows: the fissures between the interlayer of bedded rock salt is main aisles of gas permeability;it has strong gas permeability;gas permeability within interlayer is delayed the fissure between interlayer;the speed of gas permeability is decreased with time;at last,it reaches stable state.So the salt-mudstone interlayer has a great impact on permeability of long-term running gas storage cavern of surrounding rock;reasonable running pressure is the important condition to the gas storage cavern without leaking.The results can offer some frame of reference to natural gas permeability research of long-term running storage cavern.