| 2019年3月柴达木盆地茫崖5.0级地震构造与油田井损关系分析 |
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| 引用本文： | 张长好,杨屹洲,郭召杰,朱立林.2019年3月柴达木盆地茫崖5.0级地震构造与油田井损关系分析[J].地质学报,2020,94(6):1911-1922. |
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| 作者姓名： | 张长好 杨屹洲 郭召杰 朱立林 |
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| 作者单位： | 1） 中国石油青海油田分公司勘探事业部，甘肃敦煌，736202;2） 造山带与地壳演化教育部重点实验室，北京，100871；3） 北京大学地球与空间科学学院，北京，100871;4） 中国石油青海油田分公司采油三厂，青海茫崖，816400 |
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| 基金项目： | 本文为国家科技重大专项（编号：2016ZX05003-006）和国家自然科学基金重点项目（编号：41930213）联合资助。 |
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| 摘 要： | 地震引起的油气勘探开发过程中的钻井破坏日益引发关注，研究地震构造与钻井破坏之间的关系对油田安全生产非常重要。2019年3月28日青海省茫崖地区发生一系列地震，最大震级达5.0级，震中位于柴西狮子沟构造，并且在地震期间狮子沟地区钻井发生破坏。结合高精度地震勘探数据与钻井资料，本文刻画了狮子沟地区的地震构造与井损点分布特征，进一步探讨钻井破坏的原因。研究表明狮子沟构造是本次地震的发震构造，由盐上滑脱构造与盐下基底卷入的正花状构造组成，两者夹有厚度不均匀的盐岩体。在地震中被破坏的钻井集中分布于狮子沟背斜北东翼，靠近盐岩体厚度最大的区域。钻井井损点大致位于盐岩体顶面的连面且平行于地层层面。震源机制解指示存在倾向南南东、倾角较陡、以逆倾滑分量为主、兼有左行走滑分量与倾向北东、倾角较缓、兼有逆倾滑分量与右行走滑分量的两节面，分别对应盐下基底断裂的分支断裂与盐上逆冲滑脱断裂。考虑到震源位置的不确定性，盐下分支断裂或盐上逆冲滑脱断裂可能是本次地震的发震断裂，其中后者具有更大的可能性。钻井破坏的原因是同震断层活动造成的沿不稳定盐层顶面发生顺层剪切。因此，本文报道了盐构造环境下地震造成钻井破坏的实例。
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| 关 键 词： | 柴达木盆地 茫崖地震 狮子沟构造 盐层 井损 |
| 收稿时间： | 2020/3/22 0:00:00 |
| 修稿时间： | 2020/5/9 0:00:00 |
Seismotectonics of the March 2019 MW 5.0 Mangya earthquake in the Qaidam Basin and borehole damage analysis |
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| ZHANG Changhao,YANG Yizhou,GUO Zhaojie,ZHU Lilin.Seismotectonics of the March 2019 MW 5.0 Mangya earthquake in the Qaidam Basin and borehole damage analysis[J].Acta Geologica Sinica,2020,94(6):1911-1922. |
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| Authors: | ZHANG Changhao YANG Yizhou GUO Zhaojie ZHU Lilin |
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| Institution: | 1) Petroleum Exploration Division, Qinghai Oilfield Company, PetroChina, Dunhuang, Gansu, 736202;2) Key Laboratory of Orogenic Belts and Crustal Evolution, Ministry of Education, Beijing, 100871;3) School of Earth and Space Sciences, Peking University, Beijing, 100871; 4) The 3rd Production Plant, Qinghai Oilfield Company, PetroChina, Mangya, Qinghai, 816400 |
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| Abstract: | The borehole damage induced by earthquakes during hydrocarbon exploration and production is attracting growing attention. For safe production it is important to study the relationship between seismotectonics and borehole damage. A series of earthquakes, with maximum magnitude reaching M5.0, occurred on March 28th, 2019 in Mangya, Qinghai province. Their epicenters were located in the Shizigou structure and several wells in the Qaidam Basin were damaged during these earthquakes. Based on high resolution seismic and drilling data, this paper depicts the seismotectonics and the distribution of borehole damage for further investigation into the causes of the borehole damage. Results show that a suprasalt detachment structure and a subsalt positive flower structure comprise the Shizigou structure. The seismotectonics of these earthquakes involve a salt body with non uniform thickness. The damaged wells during the earthquakes are mainly located in the NE limb of the Shizigou anticline and are close to the thickest part of the salt body. A plane which roughly consists of the borehole damage points is situated on the top surface of the salt body and is parallel to the layer. The result of the focal mechanism solution shows that one plane which dips steeply to the SSE mainly thrusts with a small left-lateral strike-slip component, whereas another plane which dips gently to the NE has both thrust and left-lateral strike-slip components. The two planes represent a branch of the subsalt basement engaged fault and the suprasalt detachment thrust fault respectively. Considering the uncertainty in the hypocenter location, either the subsalt branch fault or the suprasalt thrust detachment fault could be the causative fault, though the former is more likely. The reason for the borehole damage can be attributed to detachment along the top surface of the unstable salt during co seismic faulting. Thus, this paper reports an instance of borehole damage induced by earthquakes in salt tectonics. |
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| Keywords: | Qaidam Basin Mangya earthquake Shizigou structure Salt Borehole damage |
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