COMPENSATED ELECTROMAGNETIC LOGGING ARRAY FOR USE DURING THE DRILLING OF SMALL DIAMETER WELLS

摘要

The invention relates to the field of borehole geophysics, more specifically to electromagnetic logging arrays, and can be used for measuring the electrical characteristics of rocks during the drilling of oil and gas wells, as well as for geosteering during drilling. A design is proposed for an array which comprises replaceable antenna units, has a small outside diameter, is highly reliable and has good mechanical strength. The array consists of a metal pipe with a protective jacket disposed therein for holding an electronic circuit and replaceable receiving and transmitting antenna units. In each antenna unit, triangular annular grooves are provided in the metal pipe, having narrow longitudinal slots with ferrite inserts disposed therein, and in a split bushing with narrow longitudinal through slots. The triangular annular grooves form an antenna channel, in the centre of which an antenna wire is situated, and the surfaces of the triangular annular grooves are provided with a layer of ceramic based on a mixture of aluminium oxide and titanium dioxide, which is deposited by plasma sputtering and acts both as an insulator and as a highly robust centering aid for the antenna wire.