柴西乌南地区下干柴沟组下段沉积体系研究与有利储集层预测

Study on sedimentary system and prediction of favorable reservoirs in lower segment of Ganchaigou Formation at Wunan area,west Caidam basin

在高分辨率层序地层学原理和分析方法指导下,通过对钻井和测井资料的综合分析.在柴达木盆地西部乌南地区古近系渐新统下干柴沟组下段(E31)中识别出1个长期基准面旋回(三级级层序)LSC1和4个中期基准面旋回(四级层序):MSC1、MSC2、MSC3和MSC4。识别出2种类型的沉积体系:辫状河三角洲沉积体系和湖泊沉积体系,并在等时地层格架内分析了各基准面旋回的沉积体系构成和储层砂体的发育演化。综合分析认为:在垂向上.MSC2和MSC3上升半旋回前缘分流水道砂为本区最有利的储集层段;在平面上,乌8井东北的辨状河三角洲前缘桑叶体是目前油气勘探的有利区带。

Under the guidance of principles and analytic methods of high-resolution sequence stratigraphy,and through an o- verall analysis on drilling and logging data,identified are the long-term stratigraphie base level circle(the 3rd sequence) LSC1 and the corresponding 4 middle-term stratigraphic base level circles(the 4th sequence)as MSC1,MSC2, MSC3 and MSCA in the lower segment of Ganchaigou For- mation at W unan area,Caidam basin.Two types of deposi- tional systems--namely braided river delta and lake depo- sitional ones are analyzed,and within the correlation frame- work,the eomposition of the depositional system and the fa- cies development in the cycles are studied.Analytie results show that the increasing half-cycles MSC2 and MSCS are the most favorable reservoirs,and the area in the east- north of the well Wu 8 at the edge of delta is the most favor- able regions for searehing petroleum.