柴达木盆地新生界塑性层地震地质特征及意义

Seismic and geological characteristics of Cenozoic plastic layers in Qaidam Basin and their significance

近年来,随着地震资料品质的提升,在柴达木盆地新生界路乐河组、下干柴沟组、上油砂山组共发现三套塑性层。塑性层与构造变形及油气成藏密切相关,前人针对下干柴沟组塑性层的研究已取得一定进展,但对路乐河组、上油砂山组塑性层尚缺乏系统、深入研究,导致构造形成机理仍不明确。为此,利用高品质地震资料,结合区域地质、钻测井等资料,落实新生界三套塑性层地震识别标志、岩性特征和展布范围;分析塑性层发育特征与构造样式的联系,明确构造深、浅层脱耦的主控因素。结果表明:塑性层主要发育于阿尔金山前、冷湖构造带及英雄岭构造带等;塑性层是构造深、浅层脱耦的主控因素,在塑性层发育区构造样式以薄皮构造为主,不发育区以基底卷入为主,塑性层导致构造纵向分层、平面分区;塑性层控制着构造圈闭的发育,同时也是稳定的区域盖层,控制着油气的局部富集,可形成多种油气藏类型。该成果可为柴达木盆地塑性层相关油气藏的勘探提供指导。

In recent years,owing to the improved quality of seismic data,three sets of plastic layers have been found in the Neozoic Lulehe Formation,Lower Ganchaigou Formation,and Upper Youshashan Formation in the Qaidam Basin.These plastic layers are closely related to the tectonic deformation and oil and gas accumulation in the Qaidam Basin.The previous research on the plastic layers in the Lower Ganchaigou Formation has made some progress.Nevertheless,systematic and in-depth research on the plastic layers in the Lulehe Formation and the Upper Youshashan Formation is still absent,resulting in the unclarity of the tectonic formation mechanism.For this reason,high-quality seismic data,regional geology,and drilling and logging data were availed to determine the seismic identification marks,lithological characteristics,distribution range,and thickness of the three sets of Neozoic plastic layers in the Qaidam Basin.The relationship between the development characteristics of the plastic layers and tectonic style was analyzed,and the main controlling factor of the decoupling between the deep and shallow tectonic layers in the Qaidam Basin was clarified.The results show that the plastic layers have mainly developed in the Altyn piedmont tectonic belt,the Lenghu tectonic belt,and the Yingxiongling tectonic belt.These layers are also the main controlling factor of the decoupling between the deep and shallow tectonic layers in the Qaidam Basin.As for the tectonic style,thin-skinned structures dominate the areas with developed plastic layers while basementinvolved structures dominate the areas without plastic layers.The plastic layers cause the updown stratification and planar zoning of the structures in the Qaidam Basin.Furthermore,these plastic layers control the development of tectonic traps.As stable regional cover layers in the Qaidam Basin,they also control the local enrichment of oil and gas,ultimately enabling the formation of various types of oil and gas reservoirs.The results can guide the exploration of plastic layer-related oil and gas reservoirs in the Qaidam Basin.