超大型储气库注采气对区域应力与地震活动影响的实测研究

Hutubi underground gas storage in Xinjiang is Asia's largest storage, whose injection-production adjustment ability closes to Daqing oilfield annual output. Hutubi gas storage constantly induces small earthquakes since its application in 2013 June, and thus causes some safety hidden trouble. This project plans a continuous strain observation on the North West measuring line from Hutubi gas storage to Urumqi, based on a dense strain array consisting of 13 borehole stainmeters, which was recently constructed in the northern slope of Tianshan Mountain. The additional stress field change and the stress attenuation process caused by injection-production activity will be analyzed quantitatively, and the inherent relationship between stress change and seismicity space-time image will be studied. The future seismic activity trend around the gas storage field, especially near Urumqi, will be furthermore discussed by combining other borehole strain data of the surrounding stations and comparing the stress state near the gas storage with the additional stress field in the northern slope of Tianshan Mountain. Natural earthquake usually results from long-term slow change of tectonic stress, and induced earthquakes from short-term rapid change of additional stress caused by injection-production activity. This project will not only present quantitative understanding of stress change caused by large human activities, but also provide reliable observation foundation of large gas storage activity induced earthquake study.

新疆呼图壁地下储气库是全亚洲最大的储气库，其注采调节能力（当量）接近于大庆油田年产量。呼图壁储气库2013年6月投入使用后不断诱发小震活动，给安全生产造成一定隐患。本项申请将立足天山北麓最新布建的由13台钻孔应变仪组成的密集台阵，在由地下储气库至乌鲁木齐的北西向测线上进行连续应变观测，定量分析注采过程造成的附加应力场变化和应力衰减过程，研究应力变化与地震活动时空图像的内在联系。通过联合测线周边测点的钻孔应变资料，对比场区附近地应力状态与天山北麓区域附加应力场之间的差异，探讨储气库场区周边（尤其是乌鲁木齐附近）未来地震活动的发展趋势。天然地震多由构造应力的长期缓慢变化引起，而诱发地震则由注采气时附加应力的短期快速变化引起，本项研究不但能获得大型人类活动引起地应力变化的定量认识，还对超大型储气库引起诱发地震的可能性提供可靠的观测基础。

新疆呼图壁地下储气库是全亚洲最大的储气库，其注采调节能力接近于大庆油田年产量。呼图壁储气库于2013年投入使用后不断诱发小震活动，给安全生产造成一定隐患。本项目是基于天山北麓最新布设的钻孔应变仪密集台阵，定量分析注采过程造成的附加应力场变化和应力衰减过程，研究应力变化与地震活动时空图像的内在联系，探讨储气库场区周边未来地震活动的发展趋势。.项目执行期间，主要研究如下：1、基于已有钻孔应变密集台阵，在天山北麓吐谷鲁逆断层上盘，新建了呼图壁石梯子钻孔应变观测点。2、对储气库注采过程伴生的附加应力变化与应力衰减特征进行了半定量分析，通过对11个测点附近地应变变化与储气库油气井压力变化之间的Pearson相关系数特征作分析，得到其相关性系数随着与储气库距离的增大而逐渐减小。3、研究了应力应变变化与地震活动时空演化图像之间的关系，通过分析地震的近场和远场连续应变特征，认为当地震发生时在主动盘力源方向的某些位置，可能出现与发震断层相似的同震应变过程，其应力应变变化可能比在发震断层上所观测到的现象更接近主震的受力过程。4、针对研究期内发生的典型震例，利用研究区域已有的钻孔应变观测资料，联合数值模拟方法，得到呼图壁地震的发震断层极有可能是准噶尔盆地南缘断裂附近的一条断层面倾向北的高角度逆冲型盲断层的初步结论，同时向南倾斜的低角度逆冲断层和向北倾斜的反冲逆断层是在构造挤压应力作用下共同形成的冲起构造，对北天山山前的新生代构造变形和隆升过程具有重要作用。.本项目的研究获取得到了大型人类活动引起地应力变化的半定量认识，对超大型储气库引起诱发地震的可能性提供了较为可靠的观测资料，为认识北天山山前新生代构造变形和隆升过程提供了证据。