An Image Processing Approach to Measuring the Sphericity and Roundness of Fracturing Proppants

Abstract

Before being applied in oil fields, it is necessary to evaluate the quality of the fracturing proppants, for which sphericity and roundness are the two important parameters. In this paper, we propose a new approach to the sphericity and roundness measurement of proppants based on an image processing method. First, the OTSU method is introduced to binarize proppant image, and the statistical analysis is performed to divide the image into proppant regions and non-proppant regions. Second, after filling small holes, edge curves of all proppants were obtained by the Canny operator. Third, for all 20 images in the standard template, according to their corresponding sphericity and ratios between the radius of maximum inscribed circle and the radius of the minimum circumscribed circle, a fitting curve with maximum coefficient of determination was obtained, which could determine any proppant's sphericity. Fourth, the edge curve of any proppant was divided into several segments and curve fitting method was used to obtain a curve function for each segment. Finally, the roundness of any proppant was obtained based on curvature radius of all points in the edge curve and radius of its minimum circumscribed circle. Actual proppant's evaluation experiments showed that our approach was closest to the artificial determination using a standard template in terms of precision. INDEX TERMS Sphericity, roundness, proppant, image processing.

Fracturing Proppant Quality Estimation Based on Fuzzy Connectedness and Shape Similarity

“…For proppant extraction, it is found that the threshold method, such as Otsu method [30], is effective to some extent, and From the proppant extraction experiments both for proppants of quartz sand and proppants of ceramics, the results of the Otsu method or level set method contain many regions that do not belong to proppants, and the fuzzy connectedness method has a better performance. Although the result of the fuzzy connectedness method is worse than that of the former algorithm [24], the reason is that the algorithm [24] uses the subtraction method of two images. The first image is without proppants and the second one is with proppants, meanwhile the placement plane should be fixed during image acquisition.…”

“…The comparison experimental results of different proppants with different methods include manual measurement method, Pei's method [16], the method [24] proposed by the author in 2019 named Lyu2019, Zheng's method [21], [22](based on fuzzy connectedness extraction result and S WL is selected as the sphericity) and the proposed method in this paper.…”

“…According to [24], two error functions are used to describe the closeness of sphericity and roundness by the proposed method to the manual measurement method respectively, shown in (22) and (23).…”

“…Errors of sphericity and roundness between the manual measurement method and other methods for FIGURE 10. the manual method and other methods are shown in TABLE 9, TABLE 10, TABLE 11 and TABLE 12 respectively, where the results of Lyu2019 method and Zheng's method have been converted into the values of the standard template according to the principle of proximity [24]. From TABLE 9 and TABLE 10, for proppants made of ceramics, all the four methods get the results of sphericity very close to that of the manual measurement method with small error or even no error, and for roundness, only Zheng's method has a bigger error.…”

“…In recent years, the author has been persisting in the research on the measurement method of sphericity and roundness for fracturing proppants. Some methods of using image processing technologies have been proposed to determine the quality of proppants [16], [24]. In both methods, the edge detection and corner detection algorithms have been used in the proppant processing.…”