Method and system for predicting effective reservoir in low-permeability and ultra-low-permeability sandstone

Abstract

The invention provides a method and a system for predicting an effective reservoir in low-permeability and ultra-low-permeability sandstone. The method comprises the steps that according to logging data, the shale content is obtained through a natural gamma curve and a natural potential curve; a single sand layer meeting the condition is selected as a minimum interpretation unit; the top and the bottom of the single sand layer serve as constraint conditions, and the natural gamma curve and a density curve are normalized; according to the normalized natural gamma curve, a corresponding eccentric value, a corresponding mean value and a corresponding mutation rate are obtained; according to a sand body structure layer section determined through core observation, the intersection relation between the eccentric value and the mean value of the normalized natural gamma curve is obtained, and a logging interpretation model of the sand body structure type is determined; according to the sand body structure layer section determined through core observation, a logging interpretation model of the mutation rate is determined, and a logging interpretation result of the mutation rate is obtained;and the logging interpretation model of the sand body structure type is interpreted, a sand layer corresponding to a smooth curve is interpreted as the effective reservoir, and a sand layer corresponding to a toothed curve is interpreted as a non-effective reservoir.

Description

technical field [0001] The invention relates to the technical field of petroleum exploration, in particular to an effective reservoir prediction method and system in low-permeability and ultra-low-permeability sandstone. Background technique [0002] Numerous exploration practices have shown that the low-permeability and ultra-low-permeability reservoirs have strong heterogeneity among, within, and plane distribution. Reservoirs with the same sedimentary microfacies and the same sand belt have similar physical properties, even in the same set of sand layers. In different parts of the formation, the sand body structure is very different, which seriously affects the quality of the reservoir, making it difficult to predict the effective reservoir and optimize the production and construction targets in the low-permeability and ultra-low permeability sandstone. [0003] From a geological point of view, the currently recognized mature method for studying the internal changes of sa...

AI Technical Summary

Problems solved by technology

Although this method achieves the purpose of quantitatively explaining the sandbody structure to a certain extent, the same combination of curves may represent reservoirs in different sedimentary facies belts. If there is no constraint of sedimentary facies and sedimentary microfacies, there will be strong At the same time, this method takes the sand group as the research unit, the research accuracy is low, and the evaluation of a single sand body structure cannot be realized.

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