江陵凹陷古近系新下段膏盐岩地球物理响应特征及分布预测

Geophysical responses characteristics and distribution prediction of gypsum-salt rock in the lower member of Xingouzui Formation of Paleogene in Jiangling sag

江陵凹陷古近系新下段膏盐岩非常发育,且油气成藏与膏盐岩分布关系密切。分析研究区含膏盐岩段的岩心、钻井、测井和地震等资料,发现江陵凹陷新下段膏盐岩在测井曲线上表现为低密度、高电阻率的特征;通过正演模拟认为研究区膏盐岩具有强振幅、低频率的地震响应特征,结合井—震标定,确定不同岩性在地震剖面上的响应特征存在差异;膏盐岩表现为明显的强振幅、较好连续性的地震响应特征,砂、泥岩互层沉积表现为中—强振幅、较差连续性的地震响应特征,泥岩表现为弱振幅或空白反射特征。通过地震属性提取,分析典型岩相的地震属性特征,建立研究区岩相—地震响应—地震属性的关系,并据此预测未钻井区域的岩性分布,完成研究区不同岩性分布的区域划分。最终确定江陵凹陷新下段膏盐岩主要分布于2个区域,分别为梅槐桥洼陷南部和资福寺洼陷南部。

The lower member of Xingouzui Formation（Ex）of Paleogene in Jiangling sag is rich in gypsum-salt rocks. Thehydrocarbon accumulation is closely related to the distribution of gypsum-salt rock. By analyzing the cores,logs and seis-mic data,it is found that the lithologic and the electric characteristics of gypsum-salt rocks are low density and high elec-tronic resistivity. Based on forward modeling,their seismic responses are characterized by high amplitude and low frequen-cy. Combined with well-seismic calibrating,it is found that different lithologic has different seismic response. The seismicreflection characteristics of gypsum-salt rock are strong amplitude,low frequency and good continuity. Seismic responsesof the interbeded sand and shale are characterized by strong amplitude and bad continuity. Weak amplitude reflection fea-ture appears in mudstone. By extracting the seismic attribute data,the characteristics of seismic attributes of typical facies were determined,and the relationship among lithological facies,seismic response and seismic attribute was established topredict the gypsum-salt distribution in the undrilled zone based on the drilled area in Jiangling sag. In conclusion,gypsumsaltrock in Lower Ex of Jiangling sag distributes in two areas of the southern of Meihuaiqiao subsag and Zifusi subsag.