Sequence stratigraphic analysis of the first layer, upper second submember, Shahejie formation in Pucheng oilfield

Abstract

In view of the high accuracy and predictability, high-resolution sequence stratigraphy had been extensively applied to oil exploration and gotten prominent practicable results. This article takes the first layer, upper second submember, Shahejie (沙河街) Formation from Pucheng (濮城) oilfield as an example to analyze the application of high-resolution sequence stratigraphy in reservoir study on the basis of a comprehensive study of core log data. Firstly, facies analysis of this area reveals the corresponding terminal fan system occurring where sediment-laden streams decrease in size and vanish as a result of evaporation and transmission losses. The model includes a tripartite zonation of terminal fan into feeder, distributary, and basinal zones. Secondly, electrofacies were made by well-log analysis and then matched with sedimentary facies defined by core analysis. Four electrofacies characterizing the main sedimentary facies association and depositional environments within target area are defined (channel, lag deposit, lake or flood-plain, and overflow deposits). Thirdly, related correlations based on high-resolution sequence stratigraphy were established. By observing the stacking arrangement of genetic sequences, different scales of stratigraphic cycle can be identified. Within scale and duration, the stratigraphic cycles are termed as genetic sequences, genetic sequence sets, and minor cycles.