江汉盆地江陵凹陷古近系新沟咀组含膏盐岩系沉积特征及控制因素

江陵凹陷位于江汉盆地西南部,在其次级洼陷资福寺洼陷和梅槐桥洼陷南部新沟咀组下段(新下段)沉积了一套膏盐岩层。通过钻井、测井和岩心资料的分析,明确了研究区含膏盐岩系地层的岩性、电性及物理性质特征。在此基础上,结合三维地震剖面资料及正演模拟结果,确定了研究区主要岩性组合的地震响应特征:膏盐岩与泥岩互层表现为强振幅;砂泥岩互层表现为中振幅;质纯的泥岩振幅最弱。应用井点预测与均方根振幅预测相结合的方法,对新下段膏盐岩层的分布规律进行预测,结果表明,新下段膏盐岩层在平面上的分布较为局限,相对于沙市组具有明显的向南迁移萎缩的趋势,物源、构造和沉积环境3种因素的综合作用是造成这种差异性的主要原因。

Sedimentary characteristics and control factors of gypsum-salt rocks in the Paleogene Xingouzui Formation in Jiangling Depression,Jianghan Basin

Jiangling Depression lies in the southwestern Jianghan Basin. Researches have shown that the lower member of Paleogene Xingouzui Formation in the sub-depressions of Zifusi and southern Meihuaiqiao developed a set of gypsum-salt rocks. By the analysis of well drilling,logging and core data,we summarized the lithological, electrical and physical properties of the gypsum-salt rocks combination with the 3D seismic profile data and forward modelling result,the seismic response characteristics of the main lithological association have been determined: Gypsum-salt rock and mudstone interbeds are characterized by higher amplitudes; sandstone-mudstone interbeds show median amplitudes; pure mudstone has weakest amplitude. Well-point prediction and the root mean square amplitude are applied to predict the distribution regularities of gypsum-salt rocks in the lower Xingouzui Formation. The result shows that the distribution of gypsum-salt rocks in the lower Xingouzui Formation is relatively limited on the plane,with an obvious trend of southward migration and shrinkage compared with Shashi Formation,which is mainly affected by comprehensive factors of provenances,tectonics and sedimentary environment.