It is difficult to build directional antennas for borehole radar due to the limited space available in the borehole. Recently published results show, however, that it is possible to obtain directional information even from electrically small antennas. In this paper, we use Finite-Difference Time-Domain (FDTD) modelling to optimise the design of a four-element directional antenna array, so that ...

Previously formulated scaling laws relating acoustic waveforms in boreholes to frequency, tool size and borehole diameter were investigated by repeated logging of the same test interval with different frequencies, and by logging adjacent boreholes of different diameters with the same logging system. Acoustic source frequency bands were centered on approximately 15, 20 and 34 kilohertz. Borehole...

In this paper, numerical simulations of circular boreholes under internal hydraulic pressure are carried out to investigate the energy transferred to the surrounding rock and the breakdown pressure. The simulations are conducted by using a micromechanical continuum damage model proposed by Golshani et al. (2006). The simulation results suggest that the borehole breakdown pressure and the energy...

Directional drilling techniques, based on rotary steerable systems, are used to generate complex curved boreholes. In practice, however, boreholes drilled with such systems often show instability-induced borehole spiraling, which negatively affects the borehole quality and increases drag losses while drilling. As a basis for controller synthesis, we present a directional drilling model in terms...

Boreholes with 10% or more ellipticity are not uncommon. In this paper, we consider the coupling of an incident elastic wave into a borehole of irregular cross-section and investigate the cross-mode coupling phenomenon in sonic well logging in the presence of borehole irregularity. The mode-matching method is used. Different from its original formulation, we employ the Reichel et al. algorithm ...

Cross-borehole flowmeter tests have been proposed as an efficient method to investigate preferential flowpaths in heterogeneous aquifers, which is a major task in the characterization of fractured aquifers. Cross-borehole flowmeter tests are based on the idea that changing the pumping conditions in a given aquifer will modify the hydraulic head distribution in large-scale flowpaths, producing m...

Boring logs are widely used in geological field studies since the data describes various attributes of underground and surface environments. However, it is difficult to manage multiple boring logs in the field as the conventional management and visualization methods are not suitable for integrating and combining large data sets. We developed an iPad application to enable its user to search the ...

Ground Source Heat Hump is one of the emerging technic to utilize the reservoir of geothermal energy in Europe. The crucial factor is to find the optimal length of the borehole to successfully design a heating system. The length of the borehole varies depending on the geographical area, the capacity of the heat pump and heat load of the desired building in consideration. Several methods have be...

The propagation of borehole Stoneley waves is strongly correlated with permeability of the formation. Previous studies primarily focused on the situation where the permeability is homogeneously distributed in the formation. In many in-situ situations, however, the permeability distribution of the formation is heterogeneous, due to effects such as a damaged zone around the borehole, random varia...

Seismoelectric and seismomagnetic fields generated by acoustic waves in fluid-saturated fractured borehole models are experimentally investigated with an electrode and a Halleffect sensor. In a borehole with a horizontal fracture, the Stoneley and flexural waves induce seismoelectric and seismomagnetic fields on the borehole wall and an electromagnetic wave propagating with light speed at the h...