薄互层致密砂岩储层由于层间岩性差异、纵向非均质性强等原因,导致主裂缝难以垂向扩展,提高裂缝扩展速率可有效促进裂缝穿层扩展。为研究裂缝穿层断裂过程中的率效应机制,采用人工预制水泥-砂岩试件进行了三点弯断裂试验,通过数字图像...薄互层致密砂岩储层由于层间岩性差异、纵向非均质性强等原因,导致主裂缝难以垂向扩展,提高裂缝扩展速率可有效促进裂缝穿层扩展。为研究裂缝穿层断裂过程中的率效应机制,采用人工预制水泥-砂岩试件进行了三点弯断裂试验,通过数字图像法监测了裂缝扩展至层间接触界面处时的断裂过程区(fracture process zone,FPZ)发育特征;基于断裂动力学理论,提出了考虑率效应的裂缝扩展路径预测模型。研究结果表明:低速扩展时裂缝形态曲折,FPZ呈现短、宽的现象,高速扩展时裂缝平直,FPZ呈现长、窄的特点;FPZ存在离散性,且存在相互吸引的特点,裂缝从低弹性模量岩石向高弹性模量岩石低速扩展时层间接触界面处会提前产生高应变区,导致裂缝扩展至层间接触界面处时沿层扩展,高速扩展无此现象;岩石抗拉强度与裂缝穿越单元体的平均抗拉强度呈正相关关系,低扩展速率裂缝优先沿微缺陷扩展,导致岩石抗拉强度降低,高扩展速率裂缝优先沿自相似方向扩展,穿过大量高强度单元导致岩石抗拉强度增加;裂缝与层间接触界面夹角越大,裂缝越容易穿层扩展,裂缝与层间接触界面夹角为30°时,夹角影响效果最大,夹角超过30°时影响效果逐渐下降。研究结果对水力压裂参数优化、增加水力裂缝高度、提高薄互层致密砂岩油气产量具有重要意义。展开更多
According to a new investigation in the northern Hexi corridor,the remains of two surface rupture zones were discovered on the southern margin fault of the Helishan. One rupture has a length of approximately 7km and t...According to a new investigation in the northern Hexi corridor,the remains of two surface rupture zones were discovered on the southern margin fault of the Helishan. One rupture has a length of approximately 7km and the other 10km. The two surface rupture zones might have been produced by the latest earthquake event. On the surface rupture is continuous scarp and free face caused by the rupture. The scarp is about 1 ～ 1. 5m high and on some sites,nearly up to 2m. According to the OSL results,the latest T1 terrace and higher flood plain forming in 3000a B. P. are dislocated by the fault. The above reveals the rupture age to be later than the T1 terrace. However,in the historical data and earthquake catalogue,we didn't find related information about the fault and surface rupture in this area. The 180 A. D. Biaoshi M8. 0 earthquake and the 756 A. D. Zhangye-Jiuquan M7. 0 earthquake are documented in historical data. It is inferred by textual research that the two earthquakes are related to the northern marginal fault of Yumushan in the south of the basin. Due to a lack of reliable evidence,there are still many arguments on this inferred conclusion. Thus we hold that the two surface rupture zones were produced by one of the two large earthquakes or other unrecorded historical event. The research on the activity and surface rupture of this fault can offer valuable information for the tectonic study and strong earthquake risk estimates of this region in the future.展开更多
文摘薄互层致密砂岩储层由于层间岩性差异、纵向非均质性强等原因,导致主裂缝难以垂向扩展,提高裂缝扩展速率可有效促进裂缝穿层扩展。为研究裂缝穿层断裂过程中的率效应机制,采用人工预制水泥-砂岩试件进行了三点弯断裂试验,通过数字图像法监测了裂缝扩展至层间接触界面处时的断裂过程区(fracture process zone,FPZ)发育特征;基于断裂动力学理论,提出了考虑率效应的裂缝扩展路径预测模型。研究结果表明:低速扩展时裂缝形态曲折,FPZ呈现短、宽的现象,高速扩展时裂缝平直,FPZ呈现长、窄的特点;FPZ存在离散性,且存在相互吸引的特点,裂缝从低弹性模量岩石向高弹性模量岩石低速扩展时层间接触界面处会提前产生高应变区,导致裂缝扩展至层间接触界面处时沿层扩展,高速扩展无此现象;岩石抗拉强度与裂缝穿越单元体的平均抗拉强度呈正相关关系,低扩展速率裂缝优先沿微缺陷扩展,导致岩石抗拉强度降低,高扩展速率裂缝优先沿自相似方向扩展,穿过大量高强度单元导致岩石抗拉强度增加;裂缝与层间接触界面夹角越大,裂缝越容易穿层扩展,裂缝与层间接触界面夹角为30°时,夹角影响效果最大,夹角超过30°时影响效果逐渐下降。研究结果对水力压裂参数优化、增加水力裂缝高度、提高薄互层致密砂岩油气产量具有重要意义。
基金supported by the Joint Earthquake Science Foundation (B07007)the Foundation of Base Science of Institute of Geology,CEA (DFIGCEA0607122)the Foundation of State Key Laboratory of Earthquake Dynamics (LED0607)
文摘According to a new investigation in the northern Hexi corridor,the remains of two surface rupture zones were discovered on the southern margin fault of the Helishan. One rupture has a length of approximately 7km and the other 10km. The two surface rupture zones might have been produced by the latest earthquake event. On the surface rupture is continuous scarp and free face caused by the rupture. The scarp is about 1 ～ 1. 5m high and on some sites,nearly up to 2m. According to the OSL results,the latest T1 terrace and higher flood plain forming in 3000a B. P. are dislocated by the fault. The above reveals the rupture age to be later than the T1 terrace. However,in the historical data and earthquake catalogue,we didn't find related information about the fault and surface rupture in this area. The 180 A. D. Biaoshi M8. 0 earthquake and the 756 A. D. Zhangye-Jiuquan M7. 0 earthquake are documented in historical data. It is inferred by textual research that the two earthquakes are related to the northern marginal fault of Yumushan in the south of the basin. Due to a lack of reliable evidence,there are still many arguments on this inferred conclusion. Thus we hold that the two surface rupture zones were produced by one of the two large earthquakes or other unrecorded historical event. The research on the activity and surface rupture of this fault can offer valuable information for the tectonic study and strong earthquake risk estimates of this region in the future.
