| Both acoustic sources and detectors are put in the same borehole in routine acoustic logging. The main frequent of acoustic sources are commonly comparatively high. It has high precision and particularity depict on stratum near the hole. But acoustic logging is not very good on stratum far from the hole.This is a obvious lack of acoustic logging. Seismic on the ground can detect large range. But it has low Signal-Noise, and can not particularity depict on stratum.Cross well is one of method remedy the lack of acoustic logging and seismic. It put up a bridge between acoustic logging and seismic. Cross well can acquire high precision seismic signal. It can incept direct waves, reflect waves, diffract waves, scattering waves, guide waves, canal waves and all kinds of conversion waves. Acoustic fields have abundant information. So we can obtain much more information on stratum. The application of cross well technology is increasing in recently years. Theoretical study of borehole coupling of a seismic wave obliquely incident upon a well is a typical scattering of a seismic wave , it has straightforward significance for both vertical seismic profile(VSP) and measures of cross well.This text advises the borehole coupling of an external plane SV-wave obliquely incident upon a well in the elastic formation in the first part. The theoretical expressions were solved in and out borehole about all of frequency and we also have the numerical simulation and analysis of the acoustic field in the borehole by different frequencies and different incident angles. For SV-wave incidence, the pressure in a hole is zero at normal incidence. When the incident angle is 15, 30, 45, 60 and 75 degree, the salient features of pressure in a hole is that a series of intense high-frequency resonance peaks exit at medium and high frequency. These resonance peaks is aroused by the radial resonance of liquid in the borehole. For the hard formation, these resonance peaks are very sharp. These resonance are affected by incident angle. For he medium hard formation, the resonance at 17 kHz broadens and becomes weaker as the incident angle approaches vertical. As would be expected, both resonance peaks are weaker for the medium hard formation that for the very hard formation.Actually ,the elastic formation is an ideal circs, the result above is not satisfied to the practical need. In routine acoustic logging, the Biot solid is more important. In this situation, this text advise the borehole coupling of an external plane SV-wave obliquely incident upon a well in the Biot solid. The mechanism of the resonance response of the pressure in a hole is analyzed theoretically and numerically. In both the hard and soft formation, the pressure in a hole is zero at normal incidence. For the hard formation, the rule of pressure in a hole is similar to that for the elastic formation, but the resonance peak becomes weaker. For the soft formation, the resonances are affected by incident angle largely. Because of the importance of the permeability and porocity to the exploitation of oil and gas, we detailedly discuss their effects on the pressure in a hole. In both the hard and soft formation , the effect on the pressure in a hole is affected by the frequency. The effect of permeability is obvious at 9 kHz and 17 kHz, permeability becomes smaller, and the resonance response of the pressure in a hole becomes stronger. In other frequency rang, this effect is very small. For the hard formation , at about 9 kHz and 17 kHz, porocity becomes smaller, and the resonance response of the pressure in a hole becomes stronger. As porocity becomes small, the frequency that causes the resonance response becomes high. For the soft formation, at about 9 kHz and 17 kHz, this effect is not obvious, at other frequency rand, the effect is large, porocity becomes smaller, and the resonance response of the pressure in a hole becomes smaller.For both hard formation and soft formation, the resonance response of fluid pressure is very weak out of the well. The effect of the incident angle is very large. For both hard formation and soft formation, the effect of permeability to the pressure out of the well is not large. The effect of porocity is relevant to the incident angle. For the hard formation, When the incident angle is 60 degree, the effect of the porocity to the pressure is complex. when the incident angle is other degree, the effect of the porocity to the pressure is similar to that in the elastic formation. For the soft formation, when the incident angle is 60 degree, the effect of the porocity to the pressure is not large, the porocity becomes smaller and the pressure becomes smaller.When the angle is other degree, the porocity becomes smaller, the pressure becomes larger.For the hard formation, at high frequency, the radial displacement and the vertical displacement in the well is biggest at grazing incidence and the radial displacement is larger than the vertical displacement. The framework radial displacement is bigger than the vertical displacement in the Biot solid at the grazing incidence, while it is reverse at normal incident. At low frequency, the contribution of the slow compressional wave to the seepage radial displacement is obvious. For the vertical seepage, when the incident angle is small, the contribution of the slow compressional wave is large, while bigger than the 70 degree, the shear wave is important.For the soft formation, the radial displacement and the vertical displacement in the well can reach maximum at grazing incidence. The framework radial displacement is bigger than the vertical displacement at grazing incident, while it is reverse at normal incident. For both high and low frequency, the seepage displacement is bigger than the framework displacement. The displacement in the soft formation is more than that in the hard formation.Theoretical study of borehole coupling of a seismic wave obliquely incident upon a well is a typical scattering of a seismic wave , it has straightforward significance for both vertical seismic profile(VSP) and measures of cross well.
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