Novel calculating method for rigidity coefficient of stratum

Abstract

The invention provides a novel calculating method for the rigidity coefficient of a stratum. The method comprises the following steps: performing acoustic anisotropy measurement and volume density calculation on rock core samples to obtain a stiffness coefficient and a longitudinal wave anisotropy coefficient; performing X-diffraction measurement on the rock core samples to obtain clay content; building a relation between the longitudinal wave anisotropy coefficient and the clay content; building relations between a C11 rock core and a C33 rock core as well as between a C44 rock core and a C66 rock core; calculating the clay content by using conventional logging data of a target level of a target well; calculating the rigidity coefficients of C33 ground and C44 ground of the stratum by using the longitudinal and shear wave velocities and a volume density logging curve of the target level of the target well; calculating the rigidity coefficient C11 ground of the stratum according to the relation between the longitudinal wave anisotropy coefficient and the clay content, the clay content of the stratum and the rigidity C33 ground of the stratum; calculating the rigidity coefficient C66 ground of the stratum according to the relations between the C11 rock core and the C33 rock core as well as between the C44 rock core and the C66 rock core, the C33 ground, the C44 ground and the C11 ground. By adopting the novel calculating method, the rigidity coefficient can be calculated without utilizing a horizontal shear wave velocity obtained by performing reverse calculation on extracted stoneley waves, the extracting process of horizontal shear waves is avoided, and the calculation is easy, convenient and efficient.

Description

technical field [0001] The invention relates to the technical field of oil exploration well logging, in particular to a new method for calculating the rigidity coefficient of formations. Background technique [0002] Rigidity coefficient is a key parameter necessary for rock mechanics logging evaluation in unconventional oil and gas reservoirs represented by tight oil and gas and shale oil and gas. It specifically includes C 33 、C 44 、C 11 、C 13 and C 66 and other parameters. where C 66 and C 11 The logging calculation method of these two stiffness coefficients is a difficult problem in the field of rock mechanics logging evaluation of unconventional oil and gas reservoirs in recent years. In order to solve this problem, the idea adopted by the predecessors is: firstly invert the horizontal shear wave velocity from the Stoneley wave extracted from the array acoustic logging data, and then combine it with the bulk density logging curve to calculate C 66 ; On this bas...

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Problems solved by technology

This method has obvious limitations, the main reason is that in fast formations, the sensitivity of Stoneley waves to horizontal shear wave is poor, the extraction error is large, and the reliability is low

In the article "Determining formation shear-wave transverse isotropy from borehole stoneley-wave measurements, Xiaoming Tang, Geophysics.Vol.68, No.1, 2003", it is pointed out that the method of extracting the horizontal shear wave velocity from the logging Stoneley wave is generally Applies only to slow formations

Moreover, the process of extracting the horizontal shear wave velocity from the Stoneley wave is also very complicated, and it is difficult for ordinary technicians to realize

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