Compaction-correction-based isochronous stratigraphic interface tracking and contrasting method

Abstract

The invention provides a compaction-correction-based isochronous stratigraphic interface tracking and contrasting method. The compaction-correction-based isochronous stratigraphic interface tracking and contrasting method comprises the following steps: step one, selecting a well with a clear mark layer and a clear research layer section as a standard well, taking the well as reference well for building a connecting-well section, and then flatly drawing the tops of the mark layers of the standard well and the well to be researched to build an isochronous standard reference surface; step two, estimating the ancient restoration thickness of destination bedded sandstone and mudstone; and step three, determining the isochronous stratigraphic interface of the well position to be layered according to the isochronous standard reference surface determined in the step one and the ancient restoration thickness of destination bedded sandstone and the mudstone estimated in the step two. Through the compaction-correction-based isochronous stratigraphic interface tracking and contrasting method, the practical restoration thickness of the sandstone and the mudstone can be judged through the differential compaction effect of the sandstone and the mudstone, so that the influence of the sandstone and the mudstone on the differential compaction effect can be eliminated; the accurate identification and contrast of the isochronous interface can be finally achieved.

Description

technical field [0001] The invention belongs to the technical field of basic oilfield geology, and relates to a method for tracking and comparing isochronous formation interfaces based on compaction correction. Background technique [0002] During the process of burial diagenesis, sandstone and mudstone generally have compaction, which is also confirmed by physical experiment simulation and modern deposition. Taking mudstone as an example, on the sedimentary surface in contact with water, the pores can be saturated with water up to about 90%. When the burial depth reaches 0.9-3m, a large amount of pore water in the mudstone will be discharged quickly, and the porosity will quickly decrease to 60%. Until the burial of about 30m, the porosity remains stable. If the burial depth further increases, the porosity further decreases according to the exponential function until it decreases to about 1-2%, and then remains stable again, while the initial porosity of sandstone The degr...

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Problems solved by technology

However, in this process, sandstone and mudstone behave differently, mainly due to the difference in composition and structure of sandstone. The volume compression of sandstone mainly depends on the reduction of intergranular pores, while mudstone is mainly composed of clay minerals, which have Strong adsorption force will form interlayer water with multiple water layers. For example, montmorillonite can have up to 8 water molecule layers. During the gradual compaction process, these water molecule layers will be removed layer by layer, and the molecules are arranged As the mudstone becomes denser and denser, a large amount of water molecules are discharged, and a large amount of original intergranular pore water is discharged, so the volume loss of mudstone is much greater than that of sandstone, which results in deep buried underground. In view of the above understanding, if this differential effect is ignored in the process of deep stratigraphic correlation, it will inevitably lead to misjudgment of the isochronous stratigraphic unit interface. Therefore, based on the consideration of differential compaction of sandstone and mudstone It will be very important to compare the strata of the alluvial plain

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