Method for constructing fractured tight sandstone gas reservoir water saturation model by utilizing digital cores

Abstract

The embodiment of the invention provides a method for constructing a fractured tight sandstone gas reservoir water saturation model by utilizing digital core research. The method comprises the following steps of the fractured tight sandstone gas reservoir water saturation calculation model is established based on a digital core technology; and based on the model, fracture information is provided in combination with imaging logging data, and the fractured tight sandstone water saturation is calculated by utilizing conventional logging data. According to the embodiment of the invention, the resistivity of different fracture digital rock core models is calculated, a cross plot of stratum factors and porosity is constructed, and the relationship between a cementation index and the fracture inclination angle and opening degree is established; and the relation between the resistance increasing rate and the water saturation is constructed by constructing a cross plot of the resistance increasing rate and the water saturation under the fracture condition. Finally, the two formulas are combined to establish the new saturation model related to the water saturation, the rock resistivity, thefracture opening degree and the fracture inclination angle. The model is concise, the physical significance is clear, the calculation result is more accurate, and therefore remarkable theoretical research significance and practical application values are achieved.

Description

technical field [0001] The invention relates to the fields of evaluation of unconventional oil and gas reservoirs and digital rock physics, and more specifically relates to a method for constructing a water saturation model of a fractured tight sandstone gas reservoir. Background technique [0002] Saturation is one of the cores of logging evaluation of oil and gas reservoirs. There are saturation models with different applicability for reservoirs with different characteristics and different conductive mechanisms. For fractured tight sandstone, the development of fractures not only improves the ability of the reservoir to store and migrate oil and gas, but also changes the distribution of fluids inside the rock, which brings greater challenges to the evaluation of saturation. [0003] In the prior art, the Archie formula is the most commonly used method for saturation evaluation, which links saturation with rock resistivity and porosity, laying the foundation for oil-bearing...

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Problems solved by technology

[0004] However, the applicable conditions for calculating saturation using the Archie formula are relatively strict, and it must be a pure sandstone reservoir with good physical properties

It cannot be used directly for fractured heterogeneous reservoirs

In addition, the calculation of saturation relies too much on the results of rock electrical experiments, and the cores of fractured sandstones are extremely fragile, and it is difficult to obtain complete cores with fractures under the original formation conditions, which limits the performance of rock physics experiments

For the fracture pore space, due to the presence of mud invasion, the fracture saturation is difficult to obtain, and the cementation index of the fracture in the model is difficult to calculate accurately, resulting in inaccurate calculation results of the dual pore model saturation

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