Sirawitch Nantanoi, G. Rodríguez-Pradilla, J. Verdon
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引用次数: 4
Abstract
The Bowland Shale Formation is one of the most promising targets for unconventional exploration in the United Kingdom, with estimated resources large enough to supply the country's entire natural gas consumption for 50 years. However, development of the Bowland Shale has stalled due to concerns over hydraulic-fracturing-induced seismicity. Only three wells have been drilled and hydraulic-fractured to date in the Bowland Shale, and all three have produced levels of seismicity of sufficient magnitude to be felt at the surface. Susceptibility to induced seismicity will be determined by the presence of critically stressed faults. However, such faults can go undetected in conventional interpretation of 2D or 3D seismic surveys if they are shorter than the resolution retrievable from a seismic survey, or if they have low (and in some cases even zero) vertical displacement. In such cases, the faults that cause induced seismicity may only be visible via microseismic observations once they are reactivated. To better identify fault planes from 3D seismic images, and their reactivation potential due to hydraulic fracturing, a high-resolution fault-detection attribute was tested in a 3D seismic survey that was acquired over the Preston New Road site, where two shale-gas wells were hydraulic-fractured in the Bowland Shale in 2018 and 2019, obtaining fault planes with lengths between 400 and 1500 m. Fault slip potential was then estimated by integrating the obtained faults with the formation's stress and pore pressure conditions (with the Bowland shale also being significantly overpressured), and several critically stressed faults were identified near the previously hydraulic fractured wells. However, the faults that induced the largest seismic events in the Preston New Road site, of c. 200 m in length for seismic events of magnitudes below 3.0 (as imaged with a multicomponent, downhole microseismic monitoring array deployed during the hydraulic-fracturing stimulations), could not be identified in the 3D seismic survey, which only mapped fault planes larger than 400 m in length.
Bowland页岩地层是英国非常规油气勘探最有前途的目标之一,据估计其储量足以满足英国50年的天然气消费量。然而,由于担心水力压裂引起的地震活动,Bowland页岩的开发已经停滞。到目前为止,Bowland页岩只有三口井进行了钻井和水力压裂,这三口井都产生了足以在地面感受到的地震活动水平。对诱发地震活动的敏感性将取决于是否存在临界应力断层。然而,如果断层的分辨率小于地震测量的分辨率,或者断层的垂直位移很小(在某些情况下甚至为零),那么在2D或3D地震测量的常规解释中可能无法检测到这些断层。在这种情况下,引起诱发地震活动的断层只有在重新激活后才能通过微地震观测看到。为了更好地从三维地震图像中识别断层面,以及它们因水力压裂而重新激活的可能性,在2018年和2019年在Bowland页岩的两口页岩气井进行水力压裂的Preston New Road现场进行的三维地震调查中,测试了高分辨率断层检测属性,获得了长度在400至1500 m之间的断层面。然后通过将获得的断层与地层应力和孔隙压力条件(Bowland页岩也存在明显的超压)相结合来估计断层滑动的可能性,并在之前的水力压裂井附近识别出几个临界应力断层。然而,在Preston New Road地块,对于3.0级以下的地震事件,诱发最大地震事件的断层长度约为200 m(在水力压裂增产过程中使用了多分量井下微地震监测阵列进行成像),在3D地震调查中无法识别,只能绘制长度大于400 m的断层面。
期刊介绍:
Petroleum Geoscience is the international journal of geoenergy and applied earth science, and is co-owned by the Geological Society of London and the European Association of Geoscientists and Engineers (EAGE).
Petroleum Geoscience transcends disciplinary boundaries and publishes a balanced mix of articles covering exploration, exploitation, appraisal, development and enhancement of sub-surface hydrocarbon resources and carbon repositories. The integration of disciplines in an applied context, whether for fluid production, carbon storage or related geoenergy applications, is a particular strength of the journal. Articles on enhancing exploration efficiency, lowering technological and environmental risk, and improving hydrocarbon recovery communicate the latest developments in sub-surface geoscience to a wide readership.
Petroleum Geoscience provides a multidisciplinary forum for those engaged in the science and technology of the rock-related sub-surface disciplines. The journal reaches some 8000 individual subscribers, and a further 1100 institutional subscriptions provide global access to readers including geologists, geophysicists, petroleum and reservoir engineers, petrophysicists and geochemists in both academia and industry. The journal aims to share knowledge of reservoir geoscience and to reflect the international nature of its development.