摘要
水力压裂是页岩气开采的关键技术,其是否诱导地震已成为公众热点话题与学者研究焦点。针对页岩气开采的紧迫性与地震的灾害性凸显这一急需破解的矛盾,以四川盆地页岩气开采重点区块长宁背斜为例,对该区2018年12月16日5.7级和2019年1月3日5.3级地震及其余震序列应用研究区的速度模型进行重新定位,应用页岩气勘探的钻井与地震反射资料,开展构造解析,通过复原长宁背斜的形成过程揭示地震发生的构造地质背景,进一步探讨地震形成机制。研究表明,长宁背斜为一大型基底断层转折褶皱背斜,形成背斜的断层位移量为18km,长宁背斜吸收了33%的断层滑移量;长宁背斜的志留系龙马溪组页岩发生沿下伏基底断层滑动的层平行剪切,形成微裂缝系统;基底断层的下盘断坡部位在现今复活,该区地震多沿基底断层下盘断坡及其上、下发生,背斜与向斜转折端也出现地震集中区,但沿膝折带向上地震震级减小,志留系龙马溪组中多发生2.0级以下地震。长宁背斜区的地震目前主要发生在背斜南翼,为沿基底断层下盘断坡部位活动形成的天然地震。长宁地区的地震可能与现今青藏高原向东南缘挤出的大地构造背景有关,川西南地区的早期构造在晚第四纪复活疑是产生中等强度地震的主因。建议开展页岩气开发区地震活动的科学监测。
Hydraulic fracturing is a key technology in shale gas extraction,whether hydraulic fracturing induces earthquakes has become a hot topic in the public and the focus of scholars’research.The urgency of shale gas mining and the catastrophic nature of earthquakes highlight the urgent need to study this issue.The Changning anticline at the southern margin of the Sichuan Basin is a key area for shale gas exploitation.Taking this as an example,this paper applies the velocity model of the study area to reposition the M5.7 magnitude earthquake on December 16,2018 and the M5.3 magnitude earthquake on January 03,2019 and their aftershock sequence in this area.Using shale gas exploration drilling and reflection seismic data to carry out structural analysis,and recovering the tectonic geological background of earthquake occurrence by restoring the formation process of Changning anticline,to further explore the seismic mechanism.Our results show that the Changning anticline is a large basement fault-bend fold,and the displacement of the fault forming the anticline is 18 km,and the Changning anticline absorbs 33%of the fault slip.The Silurian Longmaxi Formation of the Changning anticline experienced larger-parallel shearing along underlying basement faults,forming a micro-fracture system.The footwall ramp of the basement fault is reactivated at present,earthquakes in this area mostly occur along the footwall ramp of the basement fault and above and below it.The anticlinal and synclinal hinge zones are also the earthquake concentration areas,but the earthquake magnitude decreases upwards along the kink-band,and small earthquakes below M2.0 occur in the Silurian Longmaxi Formation.So far,the earthquake in the Changning anticline mainly occurred in the southern limb of the anticline,which is a natural earthquake formed along the footwall ramp of the basement fault.The earthquakes in the Changning area are possible related to the geo-tectonic setting for the southeast outward compression of the Qinghai-Tibet Plateau at present,the moderate or large-scale earthquakes in the southwest Sichuan Basin are mainly due to the reactivation during late Quaternary of the earlier formed faults.It is suggested to carry out scientific monitoring of seismic activities in shale gas development zones.
作者
何登发
鲁人齐
黄涵宇
王晓山
姜华
张伟康
HE Dengfa;LU Renqi;HUANG Hanyu;WANG Xiaoshan;JIANG Hua;ZHANG Weikang(China University of Geosciences,Beijing 100083,China;Institute of Geology,China Earthquake Administration,Beijing 100045,China;Hebei Earthquake Agency,Shijiazhuang 050021,China;Research Institute of Petroleum Exploration&Development,PetroChina,Beijing 100083,China)
出处
《石油勘探与开发》
SCIE
EI
CAS
CSCD
北大核心
2019年第5期993-1006,共14页
Petroleum Exploration and Development
基金
国家自然科学基金项目(41430316,40739906,41272237)
关键词
地震灾害
页岩气勘探
页岩气开采
水力压裂
流体超压
构造变形
长宁背斜
四川盆地
earthquake hazards
shale gas exploration
shale gas production
hydraulic fracturing
fluid overpressure
structural deformation
Changning anticline
Sichuan Basin
