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通过钻井岩芯、测井资料分析,库车坳陷下侏罗统阿合组可识别出6个长期基准面旋回以及20～23个中期基准面旋回。阿合组区域性隔层一般发育在长期基准面旋回上升到下降的转换位置或非对称型长期基准面旋回(只有上升半旋回)的上部。长期基准面旋回是该区建立高分辨率层序地层对比格架的基础和关键。根据层序界面特征和相序的不同,可将中期基准面旋回大致划分为三种结构明显不同的类型(向上“变深”的非对称型旋回层序,向上“变浅”的非对称型旋回层序,对称型旋回层序);中期基准面旋回是进行储层非均质性研究、储层预测与生储盖组合分析的基本单元;中期基准面旋回明显地控制了储集体的岩性和物性的变化以及沉积微相的变化。中期基准面上升的早期易形成辫状河道砂体,岩性由粗变细,孔渗由高变低;中期基准面上升的中期一般为心滩坝沉积,岩性粗细和孔渗无规则变化;中期基准面下降的中晚期易形成河口坝、远砂坝砂体,其岩性由细变粗,孔渗由低变高;基准面下降的晚期易形成水下分流河道砂体。
Through drilling cores and log data analysis, six long-term base-level cycles and 20 to 23 medium-term cycle cycles can be identified in the Lower Jurassic Aqu Formation in the Kuqa Depression. The Alaskan interbedded compartments generally develop at the transition from long-term base-level cycles to declining or in the upper part of asymmetric long-term base-level cycles with ascending half-cycles only. Long-term base-level cycles are the basis and key to establishing a high-resolution sequence stratigraphic contrasting framework in this area. According to the characteristics of sequence boundaries and phase sequences, the mid-term base-level cycles can be roughly divided into three distinctly different types of structures (upward “deepening ” asymmetric gyration sequence, upward Asymmetric cycle sequence, and symmetric cycle sequence). Mid-term base-level cycles are the basic units for reservoir heterogeneity analysis, reservoir prediction and reservoir-cap combination analysis. The mid-term base-level cycles are obviously controlled Changes in lithology and physical properties of reservoirs and changes in sedimentary microfacies. In the early stage of mid-term basement rise, braided channel sand bodies are easy to form, lithology changes from coarse to thin and pore permeability changes from high to low. Mid-term rise of medium-term baselines generally is sedimentation of heart-bank dams, irregular changes in lithology, In the mid-late stage of mid-term decline, it is easy to form estuarine and distal sand bar bodies. The lithology changes from coarse to coarse and porosity changes from low to high. In late stage of basal decline, it is easy to form underwater distributary channel sand body.