A Method for Quantitative Restoration of Water Depth in Ancient Lakes

Abstract

The invention relates to a method for quantitative restoration of ancient lake water depth. Through modern lake investigation means and lake bottom surface mudstone collection and analysis, a quantitative relational expression between geochemical elements and actual lake water depth is established, and the most suitable element for the fitting formula is optimized; Using the inheritance and comparison of organisms, the water depth environment in which they live is used as a link to determine the environmental variable parameters between modern lakes and ancient lakes, and then quantitatively reconstructs the calculation formula for restoring ancient lake water depth; in order to verify the accuracy of quantitatively restoring ancient water depth The relative paleo-water depth and pollen climate change curves restored by the sand-to-land ratio method and the Fischer graphical method were compared, and the verification results showed that the change trends were consistent, which proved the rationality and effectiveness of the method.

Description

technical field [0001] The invention belongs to the field of oil and gas exploration, in particular to a method for quantitatively restoring ancient lake water depth. Background technique [0002] Large-scale oil and gas exploration in my country's offshore basins began in the late 1970s. With the unremitting efforts of Chinese geologists, the possibility of the formation of continental oil and gas reservoirs was proposed, which opened the prelude to the discovery of many large oil and gas fields. Among them, Daqing The discovery of oil fields confirmed this theory. However, the theoretical issues of continental oil generation are essentially inseparable from the study of paleolimnology. Factors such as lake type, lake productivity, and water body properties are the main controlling factors that determine the development of source rocks in oil-bearing basins. The focus of sedimentology research is directly related to the evaluation and prediction of conditions such as source...

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Problems solved by technology

Although in a small number of studies, the range of changes in paleo-depth has been qualitatively or semi-quantitatively restored through indicators reflecting paleo-depth (such as sedimentary facies, geochemical parameters, seismic data, numerical simulation, paleontology, etc.), such as Chinese patent CN103345001A involving a A method for measuring the water depth of ancient lakes. Through drilling and logging data, the thickness of individual sand bars is read, and finally the thickness of individual sand bars is summed to obtain the water depth of ancient lakes; Chinese patent CN104932031A relates to a method for lacustrine deposition The quantitative calculation method of ancient water depth, which screens out lakes similar to today, fits the quantitative relationship between organic matter content and water depth, and inversely deduces the ancient water depth of lakes by testing the organic matter content of drilling core samples; Restoration of paleowater depth during the shrinking period of the basin—taking the southern end of the Bodong low salient as an example", involves the restoration of the water depth at the southern end of the Bodong low salient through elemental geochemistry, stratigraphic spectrum attribute trend analysis, and micropalaeontology. There is still a lack of fineness and accuracy in restoring the water depth of ancient lakes. Overall, there is still a lack of research on scientific issues such as quantitative reconstruction of ancient water depths or the temporal and spatial evolution of ancient water depths.

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