柴达木盆地尕斯断陷古近系-新近系的沉积演化规律与储集体分布

SEDIMENTARY EVOLUTION AND RESERVOIR DISTRIBUTION OF THE TERTIARY IN GASI FAULT SAG OF QAIDAM BASIN

利用岩心、岩石薄片、岩矿测试和测井等资料 ,对柴达木盆地尕斯断陷古近系新近系的沉积演化和储集体分布规律进行了研究。研究结果表明 ,该区古近系新近系下干柴沟组至下油砂山组发育了 4个三角洲沉积体 ,其前端或侧缘有碳酸盐岩的灰坪、云灰坪、藻丘和滩沉积。古近系新近系沉积在时间上均构成下部的退积型沉积序列和上部的进积型沉积序列。各地区发生进积与退积转换的时期不同 ,并且这种不同在沉积岩性的组合特征上有所反映。祁漫塔格和七个泉阿哈堤物源区的区域构造活动从下干柴组上段 (E23 )中期就开始加强 ,使得来自这两个物源区的进积沉积层序发育时期长 ,砂岩至砂砾岩的粗碎屑岩从E23 中期开始就明显增加 ,而相对高的湖平面期的细沉积物不甚发育 ;索尔库里干柴沟物源区的区域构造活动从下油砂山组 (N12 )早期才开始加强 ,使得来自该物源的进积层序发育时期短 ,砂岩至砂砾岩的粗碎屑岩于上油砂山组 (N22 )时期开始发育 ,而相对高的湖平面期的细沉积物十分发育 ;

The sedimentary evolution and distribution of favorable reservoirs of the Tertiary in Gast fault sag of Qaidam Basin were studied by the use of the data of cores, thin slides of rocks, well-logging and other data. Four deltas were developed in the area from the Lower Ganchaigou Formation to Lower Youshashan Formation in the Tertiary, and depositions of lime flats, dolomitic lime flats, algal mounds and carbonate banks were developed ahead of or beside the deltas. The Tertiary deposition consists of a retrograding sequence in the lower part and a progradational sequence in the upper part. The deposition time of reservoir-developing interval in the retrograding sequence is short, but the transformation time from retrogradation to progradation is different in different areas, which is responded on the lithological characteristics. In the Qimantage and Seven Springs-Ahati provenance areas, the regional structure movement began to be intense from the middle E\+2\-3, which makes the developing time of prograding sequences in these two areas prolonged. The coarse clastic rocks of sandstones and sandy conglomerates began to increase obviously in the middle E\+2\-3, while fine clastic rocks were less developed during high stand of lake level. The structural movements in the Soerkuli-Ganchaigou provenance area began to be intense in N\+1\-2, and thus the prograding sequence in this area was developed in a short time. The coarse clastic rocks began to be developed from N\+2\-2, while fine clastic rocks were very developed during high stand of lake level. The sedimentary characteristics in the Alaer provenance area fall between the above two provenance areas.