Schlumberger

MD Sweep Maximum Displacement Sweep Design

Overview Library

MD Sweep maximum displacement sweep design methodology achieves full power at the displacement limit of the vibrator in an efficient manner by optimally adjusting the drive rate and force level at the beginning of the sweep.

Tests show that this sweep design technique can add up to half an octave of full-power, low-frequency bandwidth over that possible using conventional sweeps.

Increasing the low-frequency content of seismic data is important in the following situations:

  • To improve inversion to acoustic impedance. Inversion requires seismic data with a bandwidth extending down to 0 Hz. The lowest frequencies (from around 0 to 3 Hz) can be supplied from well data, or in the absence of well data, from a velocity profile. By extending the seismic data bandwidth as low as possible towards 3 Hz, the results of inversion workflows are improved.
  • To increase the standout of wavelets. The vertical resolution of an event is proportional to the bandwidth of the wavelet in terms of octaves.
  • To image deep targets. High frequencies are progressively absorbed by the earth; in order to achieve resolution at depth, it is important and effective to extend the bandwidth at the low end of the spectrum.
  • To image beneath high-velocity and highly absorbing formations. In a similar manner to imaging deep targets, imaging beneath high-velocity and absorbing formations is better achieved by increasing the low-frequency content of the source signature.

WesternGeco Desert Explorer vibrators are specifically designed to maximize the benefits of MD-Sweep technology. Additionally, the Q-Land and UniQ systems are ideally suited to recording the data, as the digital single sensors do not attenuate low frequencies, whereas conventional moving-coil geophones attenuate reflection energy below 10 Hz.

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Improved Output with
MD Sweep

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