The existing methods of well-logging interpretation cannot be applied accurately to the exploration and evaluation of carbonate reservoirs because of the fracture development. Based on the fracture density obtained by core analysis in a carbonate reservoir located in the Ordos basin, the west of China, three types of fracture density (low, medium and high fracture density) of the target formation were identified. We investigated the effect of fractures on acoustic logging signals in time and frequency domain by Hilbert-Huang transform (HHT) and extracted 11 features in time domain and 9 features in frequency domain. Then, we reduced the features in time and frequency domain to three principal components by principal component analysis (PCA). Finally, a new prediction model of GA-SVM method based on Hilbert-Huang transform of acoustic logging data was reported to predict the fracture density. The results show that fracture density has a greater effect on the attenuation of IMF2 and IMF3 components for three different types of formation by empirical mode decomposition (EMD) analysis. The energies of Stoneley wave and shear wave have higher sensitivity than compressional wave. Compared with time domain, the distribution in high frequency domain has a greater correlation with fracture density by Hilbert spectrum and marginal spectrum. The correlation coefficients between fracture density and 9 features in frequency domain (R²=0.5~0.7) are better than the coefficients with 11 features in time domain (R²=0.3~0.5). Core analysis and interpretation of resistivity image logging support the validity and effectiveness of our model. The prediction accuracy using the features in frequency domain can reach to 82~90%, which is much higher than using the features in time domain with accuracy of 52~59%. The application with more information of acoustic logging data in our model can avoid the error in velocity picking, which points out the direction for the future prediction.

This study analyzes earthquake recordings from four near‐source (<10 km) stations near Fox Creek, Alberta, a region known for hydraulic fracturing‐induced seismicity. We examine the spatiotemporal variations of focal mechanisms and seismic anisotropy in the sedimentary strata. The focal mechanisms of surrounding earthquake swarms are generally consistent with the strike‐slip mechanism of the M_L4.6 earthquake, favoring a flower type of fault structure. The NE‐SW‐orientated fast splitting direction, determined from the shear wave splitting measurements, reflects the combined effects of (1) N‐S faults and (2) NE‐SW time‐dependent hydraulically stimulated fractures. The latter effect dominates the apparent anisotropy during the days leading to the mainshock, while its contributions are reduced by 60–70% after the mainshock. Loss of fluid into the fault damage zone, which causes the closure of fractures, is responsible for the observed spatiotemporal variation of seismic anisotropy near the hydraulic fracturing well.

Choristoma is a rare, benign, congenital proliferative tumor, with osseous choristoma being the rarest. Although the tumor is benign, effective identification is needed for its diagnosis and treatment. Here, we report the diagnosis and successful surgical treatment of two patients with osseous choristoma. Two patients, a young female and young male patient, were found to have a mass on the ocular surface. The tumor presented on the superior temporal bulbar conjunctiva in the first patient and on the upper eyelid in the second patient. Ultrasound biomicroscopy detected a strong echo with clear boundaries covering the lower echo, and computed tomography examination revealed calcification. Both patients underwent surgery, and histopathological evaluation of the mass showed osseous choristoma. They were treated by excision and subsequently cured. Osseous choristomas are usually asymptomatic. Our patients were cured immediately after surgery, suggesting that surgical treatment is an effective strategy.