西昆仑山前石炭系斜坡相的发现及沉积演化

Discovery of Carboniferous Platform Margin Slope and Evolution of Regional Sedimentary Facies in Front Belt of Western Kunlun Mountains

塔里木盆地西南西昆仑山前石炭系具有良好的油气勘探潜力,但至今未获得突破,沉积相分布特征及规律研究不够深入是其主要的原因之一。针对这一问题,通过系统分析塔里木盆地西昆仑山前石炭系12条野外剖面、3个钻井和一幅地震剖面沉积特征,首次在石炭系发现台地边缘斜坡相,并根据“沿坡定缘”的思路明确了区域沉积相类型、特征及沉积相分布和演化。研究表明,石炭系台缘斜坡相包括滑塌沉积、岩屑流沉积、浊流沉积和静水沉积等,沿塔里木盆地西昆仑山前呈东西向展布。早石炭世晚期和什拉甫-晚石炭世早卡拉乌依期,新藏公路以东为铁克里克古陆,新藏公路以西的台地边缘高能相带沿西昆仑山前呈自西向东条带状展布,其内侧发育潟湖相沉积,覆盖了喀什-叶城凹陷的主要区域。晚石炭世阿孜干-塔哈奇期,海侵范围扩大,古陆消失,沿西昆仑山前地区发育台缘斜坡-台地边缘-局限台地-蒸发台地相沉积体系。因此,喀什-叶城凹陷为高能相带的主要发育区,且具备良好的生储盖组合,是塔里木盆地西南西昆仑山前石炭系勘探的主要目标区。

The Carboniferous formation in front belt of western Kunlun mountains has good potential for hydrocarbon exploration,but no breakthrough has been made so far.The lack of in-depth research on the distribution characteristics and patterns of sedimentary phases is one of the main reasons for this.By systematically analyzing the Carboniferous sedimentary characteristics of 12 field profiles,3 drillings,and one 2D seismic profile in the front belt of the western Kunlun mountains,we have identified for the first time about the platform margin slope in the Carboniferous,and have defined the type and characteristics of the regional sedimentary phases,as well as the distribution and evolution of the sedimentary phases,based on the idea of“defining the margin along the slope face”.The Carboniferous platform margin slope phase includes slip deposits,debris flow deposits,turbidity flow deposits,and hydrostatic deposits,which spread in an east-west direction along the front belt of western Kunlun mountains of southwestern Tarim Basin.In the Late Early Carboniferous,Heshilafu Formation–Early Late Carboniferous and Kalawuyi Period,the east of the Xin–Tibet Highway was Tiekelike ancient uplift,and the west of the Xinjiang–Tibet Highway located a platform margin face,which stripped from west to east in front belt of western Kunlun mountains,a lagoonal face developed on its inner side,and covered the main area of the Kashgar–Yecheng Sag.In the Azigan–Tahaqi period of Late Carboniferous,marine expanded and ancient uplift disappeared,and platform margin slope-platform margin-restricted platform-evaporative carbonate platform facies developed.Therefore,the Kashgar–Yecheng Sag is the main development area of the high-energy phase face,and has a good combination of source,reservoir and cap;it is the main target area for exploration of the front belt of western Kunlun mountain carboniferous system in southwestern Tarim Basin.