阿尔金南斜坡东段鼻状构造带构造演化特征及找气方向

2011年，中国石油青海油田公司在东坪构造上钻探东坪1井，于古新统-始新统路乐河组砂砾岩中钻获工业气流，证实柴达木盆地阿尔金斜坡东段鼻状构造带存在油气资源。为寻找下一步的油气勘探重点区块，利用最新处理的地震资料及钻井数据，剖析了该区的地质结构，将鼻状构造带自造山带向盆地中央方向划分为4个部分（依次为山前高位断阶带，中部斜坡区，低位扭动隆起区和深部凹陷区），这4个部分彼此分开，却又相互关联。在此基础上，根据区域地质资料及构造应力场变化情况，将鼻状构造带自新生代以来的构造演化分为以下3期：①喜马拉雅早期（K-N₁末），由于构造反转及右行压扭走滑运动，形成Ⅰ期北西向断裂，控制了深凹陷与古隆起的展布；②喜马拉雅中期（N₂¹-N₂³），阿尔金断裂转为左行压扭走滑运动，形成Ⅱ期北东向断裂，发育低位扭动隆起；③喜马拉雅晚期（N₂³末-Q），阿尔金断裂发生强烈逆冲推覆，形成Ⅲ期平行于山前的叠瓦逆冲断层，并产生高位断阶及中部斜坡。最后，通过对生储盖组合和成藏条件的分析，指出该区高位断阶带和低位扭动隆起区为下一步油气勘探的有利区带。

Evolutional history and gas exploration direction of the nose-like structural belt in the eastern part of south Altun slope, Qaidam Basin

In 2011, industrial gas flow in the Paleocene Eocene Lulehe Formation was obtained in the exploratory well Dongping 1 on the Dongping structure drilled by Petrochina Qinghai Oilfield Company, and this verifies the oil/gas potential of the nose like structural belt in the eastern part of south Altun slope in the Qaidam Basin. In order to identify key target areas for future exploration, the newly processed seismic data and drilling information were used to analyze the geologic structure in this study area. The nose like structure belt was divided into 4 zones from the orogenic belt to the center of this basin, namely piedmont high fault terrace zone, middle slope zone, low wrench uplift zone and deep depressed zone. Based on the regional geologic data and tectonic stress field variation, the evolution of the nose like structure zone since the Cenozoic was divided into 3 periods. First, during the Early Himalayan Tectonic Period (from K to the end of N₁), the tectonic inversion and right lateral compress shear strike slip resulted in the stage Ⅰ NW trending fault, which controlled the distribution of deep sags and paleo uplifts. Second, during the Middle Himalayan Tectonic Period (from N₂¹ to N₂³), the activity of the Altun fault was transformed into left lateral compress shear strike slip, resulting in the formation of the stage Ⅱ NE trending fault and development of low wrench uplift. Third, during the Late Himalayan Tectonic Period (from the end of N₂³ to Q), the Altun fault experienced strong overthrusting, leading to the formation of the stage Ⅲ imbricated thrust in parallel to the piedmont as well as the high fault terrace and middle slope. In the end, the analysis of source reservoir cap combination and hydrocarbon accumulation conditions reveal that the high fault terrace zone and low wrench uplift zone are favorable target areas for future exploration.