Rock core sampling method

Abstract

The invention relates to a rock core sampling method. The rock core sampling method sequentially comprises the following steps of: weighing and measuring rock cores to be screened; measuring each rock core by using ultrasonic waves with different frequencies, and reading time used by the ultrasonic wave permeating the rock core, head wave amplitude after butt joint of probes and head wave amplitude after the rock core is added; combining an error analysis theory to acquire the numeric range of wave impedance of each rock core; preliminarily screening the rock cores with the intersected wave impedance numeric range under different frequencies; further screening the preliminarily screened rock cores by utilizing sound wave attenuation coefficients; and finally screening the rock cores with the intersected attenuation coefficient numeric range under different frequencies. The rock core sampling method is reliable in principle, simple in structure and convenient in operation. By the method, a large number of rock cores with the same properties for a test can be preferably selected with less time and cost; physical properties, such as mass, density and the like, and internal pore space structures of the rock cores can be quantitatively analyzed; and important significance is achieved in a rock core analyzing test.

Description

technical field [0001] The invention relates to the field of petroleum industry, and uses ultrasonic test data of different frequencies in combination with error analysis theory, core wave impedance and ultrasonic attenuation coefficient processing to realize a method for screening rock cores with similar physical properties and pore structures. Background technique [0002] In many core analysis tests, the same core is destroyed or its properties change after one experiment. Therefore, in order to carry out simultaneous and comparative experiments, multiple rock cores with the same properties (lithology, physical properties, structure, mechanical properties, etc.) must be prepared before the experiment. For example, triaxial mechanical experiment, acidification impact and acidification effect evaluation experiment, reservoir damage evaluation experiment, etc. However, rock is a special material with strong heterogeneity, and the development of internal pores, holes, and fr...

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Problems solved by technology

[0004] (1) Conventional sample selection methods can only ensure that the cores are roughly the same in lithology, but the internal pore structure and mechanical properties of the cores cannot be evaluated, and quantitative analysis cannot be done, and any of these factors may lead to the final experimental results Lack of contrast or misconceptions

[0005] (2) For cores in sand-mudstone formations with good homogeneity, the above method is effective, but for the low-permeability tight sandstone and carbonate formations developed in large quantities, due to the well-developed fractures and caves, the heterogeneity is extremely strong , the traditional method is too rough

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