Methods and systems for computing notional source signatures from modeled notional signatures and measured near-field signatures are described. Modeled near-field signatures are calculated from the modeled notional signatures. Low weights are assigned to parts of a source pressure wavefield spectrum where signatures are less reliable and higher weights are assigned to parts of the source pressure wavefield spectrum where signatures are more reliable. The part of the spectrum where both sets of signatures are reliable can be used for quality control and for comparing the measured near-field signatures to modeled near-field signatures. When there are uncertainties in the input parameters to the modeling, the input parameters can be scaled to minimize the differences between measured and modeled near-field signatures. Resultant near-field signatures are computed by a weighted summation of the modeled and measured near-field signatures, and notional source signatures are calculated from the resultant near-field signatures.

Methods and systems for computing notional source signatures from modeled notional signatures and measured near-field signatures are described. Modeled near-field signatures are calculated from the modeled notional signatures. Low weights are assigned to parts of a source pressure wavefield spectrum where signatures are less reliable and higher weights are assigned to parts of the source pressure wavefield spectrum where signatures are more reliable. The part of the spectrum where both sets of signatures are reliable can be used for quality control and for comparing the measured near-field signatures to modeled near-field signatures. When there are uncertainties in the input parameters to the modeling, the input parameters can be scaled to minimize the differences between measured and modeled near-field signatures. Resultant near-field signatures are computed by a weighted summation of the modeled and measured near-field signatures, and notional source signatures are calculated from the resultant near-field signatures.

An apparatus includes a sub with recesses along an exterior wall to receive inserts, an antenna case including a coil surrounded by a sacrificial wear portion of a material through which signals between the coil and a formation of interest may pass. An eroded outer wall of the sacrificial wear portion is restorable by application of an uncured restorative material to the antenna case. A method includes securing an antenna case having a coil there within onto a sub, surrounding the coil with a metal sleeve shield, and radially receiving and securing a multi-piece sacrificial wear member intermediate the antenna case and a retainer ring having a threaded bore. The multi-piece sacrificial wear member is replaceable after use by unthreading the retainer ring to release the sacrificial wear member for radial removal from the sub.

A method for selecting parameters of a seismic source array comprising a plurality of source elements each having a notional source spectrum is described, the method comprising calculating a ghost response function of the array; calculating directivity effects of the array; and adjusting the parameters of the array such that the directivity effects of the array are compensated by the ghost response to minimize angular variation of a far field response in a predetermined frequency range. A method for determining a phase center of a seismic source array is also related, the method comprising calculating a far field spectrum of the array at predetermined spherical angles, and minimizing the phase difference between the farfield spectra within a predetermined frequency range by adjusting a vertical reference position from which the spherical angles are defined.

A method for selecting parameters of a seismic source array comprising a plurality of source elements each having a notional source spectrum is described, the method comprising calculating a ghost response function of the array; calculating directivity effects of the array; and adjusting the parameters of the array such that the directivity effects of the array are compensated by the ghost response to minimize angular variation of a far field response in a predetermined frequency range. A method for determining a phase center of a seismic source array is also related, the method comprising calculating a far field spectrum of the array at predetermined spherical angles, and minimizing the phase difference between the farfield spectra within a predetermined frequency range by adjusting a vertical reference position from which the spherical angles are defined.

Disclosed is a geophysical data acquisition system. The system comprises a frame assembly; a set of ground engaging members connected to the frame assembly, and adapted to move the frame assembly along the ground surface; and a carrier assembly carried by the frame assembly, the carrier assembly having one or more seismic source subsystems and a drive mechanism adapted to move each of the one or more seismic source subsystems through a plurality of positions between a lowered position and a raised position and forward and rearward positions with respect to the frame assembly. The movement of each of the one or more seismic source subsystems being in coordination with the movement of the frame assembly, such that each of the one or more seismic source subsystems move to the lowered position when the frame assembly approaches one or more data acquisition points on the ground surface.

Disclosed is a geophysical data acquisition system. The system comprises a frame assembly; a set of ground engaging members connected to the frame assembly, and adapted to move the frame assembly along the ground surface; and a carrier assembly carried by the frame assembly, the carrier assembly having one or more seismic source subsystems and a drive mechanism adapted to move each of the one or more seismic source subsystems through a plurality of positions between a lowered position and a raised position and forward and rearward positions with respect to the frame assembly. The movement of each of the one or more seismic source subsystems being in coordination with the movement of the frame assembly, such that each of the one or more seismic source subsystems move to the lowered position when the frame assembly approaches one or more data acquisition points on the ground surface.

The present invention pertains to a system and method for accelerating a mass using a pressure produced by a detonation, where the mass is accelerated over a movement range using a detonation of a pressure wave generator that produces a pressure within a coupling component that is applied to a piston having a surface area that produces a resultant force, where the acceleration of the mass determines the resulting force. The resulting force may be directed vertically and perpendicular to a target media to conduct an acoustic wave into the target media. The system may be configured to direct the resulting force horizontally and parallel to a target media to conduct a plane shear wave into the target media. Two systems may be configured to direct two resulting forces horizontally and parallel to a target media to conduct a spherical shear wave into a target media, where the two resulting forces are directed in opposite directions and separated by some distance.