准噶尔盆地地层剥蚀厚度定量恢复方法研究与应用:以克拉玛依油田八区二叠系下乌尔禾组为例

Quantitative resumption method of stratum denudation thickness and its application in Junggar Basin: A case study on the Permian Lower Urho Formation in Block 8 of Karamay Oilfield

准噶尔盆地克拉玛依油田八区二叠系下乌尔禾组逐层超覆,后期受强烈冲断作用而抬升,并遭受强烈剥蚀。恢复其地层古厚度不仅能够重建该区埋藏演化史,也是油气资源定量评价的重要基础。然而,研究区勘探程度低,传统剥蚀厚度计算方法受限。针对实际地质条件与现有资料,文中利用地震地层趋势法和沉积层序分析法,在准确圈定剥蚀边界的基础上,根据邻层厚度比值法和参考层厚度变化率法,计算出下乌尔禾组三段剥蚀厚度。在此基础上,通过分析下乌尔禾组三段关键时期的沉积演化特征,建立了研究区扇三角洲沉积模式,确定了扇三角洲前缘储集相带展布范围,为今后的油气勘探提供了可靠的地质依据。

The Permian Lower Urho Formation overlapped layer by layer in the Block 8 of Karamay Oilfield,Junggar Basin.It suffered from intense denudation because of the late strong thrusting and uplif-ting.Therefore,resuming stratum palaeothickness not only can rebuild the burial and evolution history of the study area,but also is an important base of quantitative estimation of petroleum resources.However,traditional calculation method of denudation thickness is constrained by low degree of exploration.Accord-ing to actual data and geological conditions of the study area,a suite of quantitative calculation method is probed out.Based on a new way of seismic trend thickness integrated with sedimentary sequences analysis, denudation boundary of the Permian Lower Urho Formation has been outlined.A composite method of the thickness ratio of nearby layers and the change ratio of reference layer thickness have been applied in cal-culating true denudation thickness of the Member 3 of Lower Urho Formation.By analyzing evolution char-acteristics of the Member 3 of Lower Urho Formation in the key sedimentary periods,a sedimentary model of fan delta has been established in the study area.The distribution range of delta front subfacies is also de-picted at the same time,which can provide reliable geological evidence for the future petroleum explora-tion.