Research Of The Earthquakes Induced By Water Injections In Borehole 3P Of Wenchuan Earthquake Fault Zone Scientific Drilling

In this paper it were summarized that significance of scientific drilling. On 12 May,2008, a destructive earthquake of magnitude Ms8.0 struck the Longmen Shan resign,Sichuan province,China.During the special period after the Wenchuan earthquake and the aftershock is still ongoing,Ministry of Science and Technology,Ministry of Land and Resources and China Bureau of Seismology rapid science drilling on the Wenchuan Earthquake Fault Zone(WFSD).The WFSD project plans to drill five science wells on the hanging wall of the co-seismic surface rupture zone,including the Yingxiu-Beichuan fault and the Anxian-Guanxian fault in Longmenshan area. The water flooding experiment site location is located on the wenchuan earthquake fault scientific drilling project WFSD-3P hole, the hole located on the hanging wall of the Anxian-Guanxian fault.The purpose of the research of the earthquakes induced by water injections in borehole is to study the behavior of the fluid to the fault through this experiment.From November 28, 2012 to March 9,2013,we conducted a 101-day water injection induced earthquake experiment, during the experiment, will receive the flow date, pressure, micro seismic data, geoelectric data and other meteorological data. This experiment using the experience of German continental ultra deep well drilling water injection induced earthquake experimental, by controlling the flow rate of injection,then observe the changes of pressure. During the experiment, the pressure will be change with the flow changes. Through the layout of earthquake observation network, we can monitor the micro seismic events.Through long-term observation and analysis of the data, the experiment got the relationship between flow,pressure and micro earthquake events in every day. The total amount of water injection achieved 47520 m3, in the first 4 days of the experiment,the pressure increased quickly,then after about 1 month,pressure was slowly rising, until December 28, 2014, the pressure reached maximum. For the next 3 days, the pressure droped slowly, until January 1,2014, pressure suddenly decreased rapidly. In the next few days, the pressure changed was not big,the number tended to be stable in addition to the pressure of low value in January 16,2014. On February 26, 2014, the pressure suddenly drops rapidly again.By analyse the recorded 824 seismic events, we can found that the earthquake events has increasing trend within a few days when the pressure suddenly droped. Experimental results show that the distribution of earthquake rupture location and the top and bottom interface of fault gouge in Anxian-Guanxian fault have a quite close relationship, analysis that may be caused by fault rupture again which caused by water injected lead to formation leakage.The results show that the experiment purpose of artificial water injection induced earthquake is reached.