Rock physics calculation method and system for saturation of natural gas hydrate in well

Abstract

The invention provides a rock physics calculation method and system for saturation of natural gas hydrate in a well. The method comprises the following steps: obtaining the porosity of a stratum in the well through calculation according to the data of a work area; obtaining the stratum optimal consolidation coefficient of the current depth point through inversion; calculating the stratum porosityand the consolidation coefficient in the well at each depth point in the well to obtain the stratum porosity and the consolidation coefficient of the whole well section; utilizing a three-phase Biot model to predict stratum longitudinal wave speed and stratum density, and calculating hydrate saturation of each depth point in the well by taking a correction coefficient as a constraint; adjusting the correction coefficient by modifying the weight factor, calculating the saturation average value of the hydrate-free horizon in the well by using the new correction coefficient as a constraint, and obtaining the weight factor of the well until the saturation average value of the hydrate-free horizon approaches 0; and recalculating the hydrate saturation of each depth point in the well by utilizing the weight factor of the well to obtain the hydrate saturation value of the whole well section.

Description

technical field [0001] The invention relates to the technical field of natural gas hydrate saturation estimation, in particular to a petrophysical calculation method and system for natural gas hydrate saturation in wells. Background technique [0002] Natural gas hydrate is referred to as "hydrate", also known as "combustible ice". It has become a hot spot in current energy research. Quantitative evaluation of gas hydrate reservoirs is the basis for hydrate development and utilization and environmental impact, and accurate prediction of gas hydrate saturation is crucial for quantitative evaluation of hydrate resources. [0003] At present, the methods used to estimate and evaluate the saturation of gas hydrate reservoirs, in areas where drilling data exist, resistivity logging and acoustic logging are effective means for evaluating gas hydrate reservoirs. From an electrical point of view, Archie's formula (Archie, 1942), two-water model, and Nidonisian formula are used to ...

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Problems solved by technology

[0004] However, the existence of hydrates will not only change the sound velocity of the formation, but also affect parameters such as formation density and consolidation coefficient. Therefore, it is not enough to estimate saturation only by formation sound velocity, which will affect the accuracy of the results; in addition, different Hydrate saturation estimation methods or petrophysical models are suitable for different regions and occurrence states, and the settings of many parameters in the model will affect the saturation estimation results

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