Approximate and exact formulations are presented for the interaction of an incident wave with a cased borehole. In the approximate method, the borehole coupling theory is used to compute pressure in the fluid at a low frequency. The results are simple and explicit. They are useful in the study of cased borehole coupling and as well as borehole radiation. In the exact method, elastic potentials ...

Horizontal drilling is an important development in the petroleum industry and it relies heavily on guiding the drill bit with the aid of sonic logging, i.e. geosteering. The quality of sonic imaging depends heavily on the effective suppression of borehole waves and enhancement of weak reflection signal. To this end, we propose an approach to image the near-borehole structure using acoustic logg...

Minimum-structure inversion has been widely used in both hydrocarbon and mineral exploration for decades. However, models obtained with this method typically exhibit smooth variation of physical properties and smeared-out boundaries, and may not give detailed information about the target being investigated. In this paper we present a constrained joint inversion of surface and borehole gravity t...

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 ...

Introduction: Cavities of secondary calcite and veins of secondary anhydrite and quartz in the Yuca-tan-6 borehole drilled into the Chicxulub structure suggested the impact generated a hydrothermal system [1, 2]. Based on work at other craters, mostly Siljan and Puchezh-Katunki [3, 4], we estimate this system could be several kilometers deep in the center of the crater and may extend to the rim...

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...

Introduction: The exploration of the Martian surface by the rovers Spirit, Opportunity, and Curiosity has indicated the widespread presence of clastic rocks of basaltic composition [1-3], many of which have altered to various extents. In this investigation, we have examined basaltic ash and tephra formed through hy-drovolcanism (the explosive interaction of magma with liquid water), glaciovolca...

The goal of this work was to study the diversity of microorganisms inhabiting a deep subsurface aquifer system in order to understand their functional roles and interspecies relations formed in the course of buried organic matter degradation. A microbial community of a deep subsurface thermal aquifer in the Tomsk Region, Western Siberia was monitored over the course of 5 years via a 2.7 km deep...