基于现代沉积的车排子凸起春光区块沙二段沉积相研究

Research on Sedimentary Facies Based on Modern Sedimentary Systems:A Case from the Second Member of Shawan Formation in Chunguang Area of Chepaizi Swell,Junggar Basin

准噶尔盆地车排子凸起春光区块中新统沙湾组沙二段取得油气勘探突破,但对其沉积体系的认识争议很大,沉积相类型难以确定,加大了单砂体精细刻画、内部构型及储层建模等精细研究的难度,阻碍了该区岩性油气藏勘探开发的进程。综合岩心、测井、测试分析及高精度三维地震资料,通过分析现代沉积的遥感图像特征,与甘肃省玛曲河及俄罗斯勒拿河三角洲沉积特征进行比较,研究结果表明,研究区沙二段为辫状河三角洲沉积体系,发育辫状河三角洲平原和辫状河三角洲前缘亚相,主要沉积微相为分流河道、水下分流河道和分流砂坝,砂体发育。研究区岩性圈闭带形成的主要原因是较为发育的分流间湾导致分流河道和分流砂坝砂体的横向不连续,形成孤立的圈闭;研究区东南部由于不存在沉积的横向间断,较难形成有效圈闭。

Great breakthrough has been achieved in the second member of Shawan formation in Chunguang area of Chepaizi swell, Junggar basin. However, there are a lot of discussions about its depositional system. The uncertainty of its sedimentary facies adds some difficulties to fine description of sandbody and detailed study on sandbody internal configuration and reservoir modeling, which slows down the process of petroleum exploration and development for the lithological reservoirs in the area. Based on the data of core, logging, testing and high-resolution 3D seismic and the analysis of remote sensing images of modem sedimentary systems, the sandbody distributions in the area are compared with those of Maqu river in Gansu province and Lena delta in Russia. The results show that the second member of Shawan forma- tion belongs to braided river delta sedimentary system, where braided river delta plain and braided river deha front are developed, the main sedimentary microfacies can be divided into distributary channel, underwater distributary channel and distributary sand bar and sandbod- ies are well developed. The reason of the formation of the lithological trap belt in the study area is the lateral continuity of the distributary channel and distributary sand bar resulted from the developed distributary bays, which leads to traps isolated from each other; it is hard to form efficient traps in the southeast of the area due to the lack of transverse breaks of deposits.