Seismic instruments: article

Using four-component geophones - effect on quality and reliability of multicomponent seismic recording, analysis of processing methods
P. Plotnitskii1,2
S. Yaskevich1,2
A. Duchkov1,2
1 Trofimuk Institute of Petroleum Geology and Geophysics, Siberian Branch of Russian Academy of Sciences, Novosibirsk, Russia
2 Novosibirsk State University, Novosibirsk, Russia
Journal: Seismic instruments
Tome: 53
Number: 4
Year: 2017
Pages: 26-36
UDK: 550.34, 550.34.038.8
DOI: 10.21455/si2017.4-2
Keywords: borehole geophone, components, recording, tetrahedron, multiwave seismology, polarization analysis, microseismic monitoring, noise suppression, VSP
Аnnotation: For seismic observations in mines or wells, along with three-component seismic sensors, four-component geophones with sensors located along the tetrahedron axes are used. When the geophones are placed in a hard-to-reach place for a long period, the requirements for the sensor reliability increase, and there is a need to control its operation. From this point of view, the four-component geophone has some advantages over the conventional three-component one. Of these advantages, three main ones are distinguished: the suppression of instrumental noise when recalculating the four-component recording into a three-component one, retaining the informative value of the polarization analysis of the data in a case of failure of one of the components of the seismic receiver, and monitoring the sensitivity of individual components of the seismic receivers. To suppress instrumental noise in the case of a four-component geophone, it is necessary to perform a number of procedures: first, the covariance matrix of the recording components is calculated, next, the eigenvalues and eigenvectors of the covariance matrix. Then a parameter is calculated that allows us to assess the ratio of instrumental noise to the useful signal. On the next step, we calculate an operator which converts the four-component record into a three-dimensional subspace projection. This operator is applied to the data to suppress interference (movements that do not correspond to motion in three-dimensional space). At the output of the procedure, we get the data, partially separated from the instrumental noise. In this paper, the data processing features of four-component geophones are studied using model examples. The capability of suppressing instrumental noise and controlling the sensitivity of individual components of seismic receivers is demonstrated. We also show and analyze the effect of polarization analysis on the results obtained.