Method for determination of porosity of rock seals

Abstract

The invention provides a rock storage porosity measurement method. The method comprises the following steps of measuring the initial porosity of a rock sample, obtaining the porosity under each particle size gi in a step-by-step crushing way, and calculating the storage porosity of the rock sample under each preset particle size gi according to a formula, wherein pores are randomly opened during the crushing at each time, the storage large and small pores are both probably opened, the rock sample comprises fewer storage pores and more storage pores are opened if the particle size is smaller, and when the porosity of the rock sample is close to a limit value, the storage pores in the rock sample are determined to be all exposed. According to the method, the storage porosity of rocks can be accurately obtained, so that the porosity of the rocks can be accurately obtained, and accurate data basis can be provided for the computation of air content of shale.

Description

technical field [0001] The invention relates to an experimental measurement method, in particular to a method for measuring the closed porosity of rocks. Background technique [0002] The study of rock pores is of great significance to oil and gas reservoirs. Pores are the main space for oil and gas accumulation, and porosity is the most important standard to measure the number of pores. For unconventional oil and gas reservoirs with tight sandstone and shale lithology, correct porosity measurement determines the accuracy of gas content calculation. Pores in rocks are mainly divided into two categories, one is connected pores and the other is closed pores. [0003] The current porosity measurement methods, such as Boyle's law single-chamber method and double-chamber method, are used to measure the connected porosity of rocks, and cannot measure the closed pores in rocks and the formation of oil due to the plugging effect of oil on rock pore throats. The closed pores were m...

AI Technical Summary

Problems solved by technology

Another type, such as microscopic observation and scanning electron microscopy, can only observe the two-dimensional pore structure on a certain section of the rock; micro-CT cannot detect closed pores smaller than 1 μm. It is impossible to measure tight sandstone; although nano-CT can measure closed pores less than 1 μm, this method can only observe samples of tens of microns, and it is very difficult to obtain the closed porosity of large rocks. The detection accuracy of nano-CT cannot reach 50nm, and the closed pores smaller than 50nm in mud shale have a large proportion, and these closed pores have a large specific surface area, which is the main storage space for shale adsorbed gas

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