A.I. Konkov* (Geodevice LLC), N.A. Rogozin (Institute “Orgenergostroy”), V.I. Ignatev (Geodevice LLC), A.N. Oshkin (Moscow State University)
Crosshole seismic testing is a technique developed and applied in practice in the first half of the 20th century (see (Butler and Curro, 1981) for the basics of the method). Li, 1994 states that the first documented seismic application involving buried sources and geophones can be found in a U.S. patent claimed in 1917 by Fessenden, who used a crosshole geometry for imaging the geologic region between boreholes locations. Apart from surface seismic methods, crosshole seismic testing has some advantages, the main of which is that one can bring nearer the subject of research to sources and receivers. Therefore, taking into account the inhomogeneous absorbing near-surface layer is not necessary. Apart from well logging operations, the coverage area of the near-hole space in the method is incomparably larger and can reach hundreds of meters.
Crosshole Seismic Testing
At the moment, there are 4 main designs of the crosshole seismic testing exist: a) single-beam parallel probing with pressure waves, b) multiwave parallel probing, c) tomographic probing with pressure waves, d) multiwave tomographic probing. In more sophisticated realizations of the method, the day surface is taken into account during observations or studies are conducted in shafts and galleries in an arbitrary plane. When preparing boreholes for the multiwave tomographic probing, it becomes necessary to ensure a good mechanical contact of the casing with surrounding rock. The most reliable way to ensure such contact is the cementation of casing-formation annulus, the process of which is described in details in ASTM D 4428 / D 4428M standard.