泌阳凹陷白云岩系高分辨率层序地层格架——一个应用基准面旋回理论的实例

HIGH-RESOLUTION SEQUENCE STRATIGRAPHIC FRAMEWORK OF DOLOMITE ROCKS IN BIYANG SAG:A CASE STUDY OF THE APPLICATION OF BASE LEVEL CYCLE THEORY

根据基准面旋回理论 ,通过对研究区内 4条连井剖面的层序地层分析 ,建立起核桃园组三段 1亚段至二段 3亚段 (C1)、核桃园组二段 2亚段至 1亚段 (C2 )两个长期基准面旋回 ,其界限是基准面上升到基准面下降的转折点。C1旋回纵向上为一个水体由深变浅的序列 ,可进一步划分为MSC1和MSC2两个中期基准面旋回 ,相当于核桃园组三段 1亚段和二段 3亚段的沉积 ;每一个中期旋回当中可再细分为小的短期旋回。C2旋回纵向上不完整 ,仅由一个基准面下降的半旋回组成 (相当于核桃园组二段 2亚段到 1亚段的沉积 ) ,可进一步划分为MSC3,MSC4 ,MSC5和MSC6中期基准面旋回。在已建立的层序地层格架基础上进行精度更高的层序划分 ,将有助于泌阳凹陷白云岩区的微相研究 ,从而可预测与油气藏形成有紧密联系的裂缝和溶孔发育的有利相带。

Based on the base level cycle theory, two long-term base level cycles,i.e.C1(the 1st sub-member of 3rd member of Eogene Hetaoyuan Formation(Eh 31)—the 3rd sub-member of 2nd member of Eogene Hetaoyuan Formation(Eh 23)) and C2(Eh 22-Eh 23),have been built up through the sequence stratigraphy analysis of 4 well-to-well correlation sections in the study area.Their boundaries might be a breakpoint where base level rises and falls. C1 cycle is vertically a sequence which water body shallows upwardly,and it can further be divided into two medium-term base level cycles,i.e.MSC1 and MSC2,corresponding to the Eh 31 and Eh 23 deposition. Each medium-term cycles are subdivided into smaller short-term cycles. C2 cycle is vertically not complete and is only composed of one half cycle with a fall in base level (equivalent to Eh 22 and Eh 21 depositional stages), which can further be divided into four medium-term base level cycles, i.e.MSC3, MSC4, MSC5 and MSC6. On the basis of the established sequence stratigraphic framework, a more detailed sequence classification will be helpful to study the microfacies of dolomite area in Biyang sag, and to predict the facies belts favorable for development of fractures and dissolved pores closely related to oil and gas accumulation.