讲座题目：Geomechanics and Shale Gas Development: The Relationships Among Microearthquakes, Fault Slip and Permeability Enhancement During Slickwater Hydraulic Fracturing 

报告人：Prof.  Mark Zoback

时 间：3月25日（周五）下午2:00-3:30
地 点：英杰交流中心第二会议室
主持人：龚斌（特聘研究员）

报告内容摘要：
     In this paper we illustrate several unusual phenomenon discovered during investigation of multi-well, multi-stage slickwater hydraulic fracturing operations in the Barnett shale that may have important consequences for the development of enhanced permeability in shale gas reservoirs. Forty hydraulic fracturing stages were carried out in five parallel, horizontal wells, drilled about 500 ft apart. While the pumping rates, duration, volume of proppant in each of the stages were nearly-identical, they were carried out in a variety of sequences. With a seismic monitoring array deployed in the middle well, the frac stages in the two wells to one side were frac’d simultaneously, starting at the toes of the well and proceeding toward the heels. The two wells on the other side were frac’d sequentially (“zipper frac’d”) again from the toe to the heel. In both cases, the seismic array was moved in the horizontal well to minimize the distance between the induced microseismic events and the seismic monitoring array.  Finally, the middle well was frac’d in a conventional manner, with the seismic array being deployed in the vertical section of one of the wells.
      After correcting for the inability to detect the smallest seismic events at larger distances, we found a systematic increase in the number of induced microseismic events with frac stage. Despite the fact that the rates and amounts of fluid that were pumped in each stage was essentially the same, the number of seismic events in a given stage increased markedly in the stages closer to the heel of the well, before dropping off right at the heel.
      The shut in pressures systematically increase with distance with stage number (distance from the toe of the well). In wells A, B and C, the shut in pressure decreases from its maximum value in the stages closest to the heel of the well. The facts that both the number of earthquakes and shut-in pressures increase with stage number, there is a correlation between shut-in pressure and the number of microseismic events induced in any given stage. We are examining a variety of physical models to examine the cause of the increase in shut-in pressure with depth. These include the cumulative effects of fracture propping and poroelastic effects.
      In addition to microseismic events in this data set, we’ve discovered long period, long duration (LPLD) seismic events. We can demonstrate that they come from the reservoir and believe they represent slow slip on faults during slick-water frac’ing operations.
      The implications of these results for estimating the stimulated rock volume during hydraulic fracturing operations as well as optimizing hydraulic fracturing operations.

报告人简介：
      Mark D. Zoback is the Benjamin M. Page Professor of Geophysics at Stanford University. He is also co-director of the Stanford Rock Physics and Borehole Geophysics industrial consortium and the current President of the American Rock Mechanics Association. Dr. Zoback conducts research on in situ stress, fault mechanics, and reservoir geomechanics. He is the author of a textbook entitled Reservoir Geomechanics published in 2007 by Cambridge University Press. He is the author/co-author of 300 technical papers and holds five patents. Dr. Zoback has received a number of awards and honors, including the 2008 Walter H. Bucher medal from the American Geophysical Union. In 2011, he was elected to the National Academy of Engineering. He was the co-founder of GeoMechanics International in 1996, where he was Chairman of the Board until 2008. He also currently serves as a Senior Executive Adviser to Baker Hughes, Inc.