Detection of subsurface fractures and permeable zones by analysis of tube waves

Abstract

In Vertical Seismic Profiling tube waves are generated by compressional waves impinging on subsurface fractures or permeable zones. The amplitude of tUbe waves is dependent upon the formation permeability, the length of the fracture, and on the source frequency. The generation of tube waves is formulated theoretically and the relative effects of these parameters are studied individually. Field examples are shown for open fractures in granite. From tube wave amplitudes normalized to P-wave amplitudes, calculated permeabilities are on the order of 400 millidarcys.

Application of full waveform acoustic logging data to the estimation of reservoir permeability

“…Therefore, permeability detection from acoustic surveys could add much value to the full waveform acoustic logging method. This result can be reached, starting from the physical situation rather than from the general expression of the conservation equation (Beydoun et al, 1983). …”

Detection of open fractures with vertical seismic profiling

“…The fluid pulse mechanism for the generation of tube waves has been formulated mathematically by Beydoun et al (1983). The geometrical model used in that study is that of a parallel-walled open fracture intersecting a borehole.…”

“…the in situ fracture permeability can then be estimated from the ratio of the tube wave amplitude to the P wave amplitude measured in the formation or in the fluid. The model used in Beydoun et al (1983) assumed a vertical borehole, a horizontal fracture perpendicular to the borehole, and a vertical incident P wave normal to the fracture. In this paper we have extend this model to include random orientations of the borehole, fracture and the incident P wave.…”

“…The theory for the parallel wall fracture model has been discussed in some detail in Beydoun et al (1983) for the vertical borehole, horizontal fracture and vertical incident P wave. In the following section, we will present the corresponding theory for the angle dependent model.…”

“…and we are presenting here the essential results that are different from the previous model. The reader is referred to Beydoun et al (1983) for the more basic details.…”