Shale bed sequence stratigraphic division method

Abstract

The invention provides a shale bed sequence stratigraphic division method. The shale bed sequence stratigraphic division method comprises the steps of 1, extracting a rock core sample and obtaining element data and fabric features; 2, according to element features, analyzing environmental evolution features including paleoclimate, paleowater depth, paleosalinity and paleoredox; 3, determining parasequence set boundary features according to sequence cycle standards by a sequence stratigraphy principle; 4, establishing corresponding relationships between a natural gamma curve and a parasequence set and between the natural gamma curve and a sequence boundary, and establishing a stratigraphic framework profile; and 5, performing full-region sequence stratigraphic division, drawing a sequence stratigraphic distribution plane graph, and analyzing a sequence stratigraphic distribution law. The shale bed sequence stratigraphic division method solves two difficult problems of sequence boundary identification and full-region sequence stratigraphic fine correlation; and the whole method is high in operability and provides effective technical support for exploration deployment of shale oil and gas.

Description

technical field [0001] The invention relates to the field of sequence stratigraphy, in particular to a method for dividing mud shale sequence stratigraphy. Background technique [0002] Unconventional shale oil and gas resources are becoming one of the important targets of oil and gas exploration, and they are an important field and backup position for exploration. Compared with the series of coarse clastic rocks and carbonate rocks, the research on the sequence stratigraphy framework of mud shale is still shallow. Traditional sequence stratigraphy divides the mud shale section as a sequence, that is, the lacustrine transgressive system tract, and does not carry out fine calibration and analysis inside it, but the mud shale is not the same homogeneous body in stratigraphy and space , there are a variety of three-dimensional transported sedimentary structures, structures and different lithofacies types. How to describe the heterogeneity of shale? Under what geological scal...

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Problems solved by technology

In genetic sequence stratigraphy, the largest lake flooding surface is used as the sequence boundary, which is conducive to the identification of systems tracts, but it is not conducive to the sequence stratigraphic correlation of the whole region

The gamma spectrum cycle analysis method is mainly based on the different lithofacies combination patterns of various lithofacies types in mud shale due to the change of depositional environment in the process of relative sea level rise and fall. Transgressive erosion surfaces are the key to establishing sequence stratigraphy, gamma spectrum cycle analysis is good for the whole area correlation, but it is difficult to identify sequence boundaries

The chemical sequence stratigraphy method closely combines quantitative stratigraphy and chemical stratigraphy by analyzing and studying the abnormal change rules of chemical elements and stable isotopes near the stratigraphic interface, and studies the characteristics of stratigraphic division and correlation in the strata. The distribution of chemical elements and stable isotopes is used to discuss the division and correlation of stratigraphic boundaries. The chemical sequence stratigraphy method is conducive to the identification of sequence boundaries, but it is not conducive to the stratigraphic correlation of the whole region

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