Discussion on the Correlation Methods of Base-level Cycle and Sedimentary Cycle Sequence

Key words: 
• reservoir correlation /
• sedimentary cycle /
• base-level cycle /
• Daqing oilfield

Abstract: It is the research goal of the development geology to build up high-resolution isochronous sequence framework, quantitatively study the division and correlation of the reservoir genetic units and provide the basis for developing small-scale flow-units in Daqing oilfield. The paper points out that there are currently two methods on reservoir division and correlation, i.e. base-level cycle and sedimentary cycle, and the marrow of the high-resolution sequence division is the correlation of the base-level cycle. The key of the detailed geological description and correlation of Daqing oilfield is the correlation of sedimentary cycle. Thus, the author expounds the similarities and differences between the high-resolution sequence stratigraphy and detailed geological description and correlation of Daqing oilfield on such aspects as principles, methods and theory. This research also indicates that the theoretic basis of the two methods is cycle and sequence, and their research object is sequence framework and the scale of sedimentary sequence units. The combination of different cycles is very important in correlation of base-level cycle. It can be used in lacustrine facies analysis, but difficult in fluvial facies analysis and with some uncertainties. Sedimentary cycle exists diachronism in fluvial facies and lacustrine facies, but it can be used widely. The movement of base-level cycles of the different grades makes the difference in cycles and scales of sedimentary cycle, resulting in the grade of the sequence, therefore, base-level cycle and sedimentary cycle approach the same object from different ways. Furthermore, the paper discusses two key problems about cycles and correlation, i.e., sequence and boundaries, and their relevant questions. Finally, the author points out their important significances in studying the flow units and distribution of remnant oil.