Sedimentary Microfacies Of Chang4+5Member Of Yanchang Formation In Qilicun Oil Field

On the basis of absorbing and summarizing previous studies, combining outcrop, core observation, rock casting slice, cathodoluminescence, electron microscopy scanning and other test data and collecting comprehensive the logging map, drilling comprehensive geological map and cuttings description records of nearby500wells from the study area and its adjacent area. Summarize sedimentology, petroleum geology, structural geology, reservoir geology, logging geology and latest progress, based on the regional geological setting in Mesozoic of Ordos Basin, this thesis makes a comprehensive study of the chang4+5sedimentary facies, sedimentary facies and distribution of sand body characteristics and regularity.Selected K4, K5, K6, as the mark layer in this study, taking into account the principle of a combination of sedimentary cycle and rock thickness, and wells nearby contrast close, analysis and comparison of the439wells, made a basic program of stratigraphic division in this area, which could be divided into four small layers. This area is a west-dipping monocline, some area has low amplitude nose-shaped uplift, even there are some differences among the structure of the reservoir group, but it keeps good inheritance.Through field outcrop and core observation, on the basis of modern sedimentology theory, took the sedimentary facies marks(such as lithological association, sedimentary structure, grain size distribution characteristics of sandstone, sand body morphology, paleontology and logging curve combination) as a clue, proceed from the sedimentary facies maps and sand body isopoch maps, we summarized that target zone developed meandering river delta depositional developed, which mainly developed meandering rever delta plain of sub-facies, which can be further divided divided into5micro-phase.Based on the confirmation of the types of sedimentary facies and micro-phase, we concluded the sand body of underwater distributary channel which has better properties, are good reservoir in study area.