Abstract: A method and system for telemetry through a drilling fluid during drilling is disclosed. A reflector (110) is positioned downstream from the drilling mud pumps (80) and causes reflected pressure waves having the same pressure polarity as incident pressure waves traveling upwards. At least one pressure sensor (92) is positioned below the reflector (110) to sense pressure in the drilling fluid. The reflector can be a fixed orifice plate or an adjustable aperture.

Abstract: A method and system for telemetry through a compressible drilling fluid during underbalanced drilling is disclosed. A reflector (110) is positioned downstream from the gas inlet (84) and causes reflected pressure waves having the same pressure polarity as incident pressure waves. A pressure sensor (92) is positioned below the reflector to sense pressure in the compressible drilling fluid. The reflector (110) can be a fixed orifice plate or an adjustable aperture. A borehole communication system is also disclosed wherein a pair of pressure sensors are positioned on either side of a flow restriction (118) located in the gas conduit leading to the gas injector. The flow restriction can be a valve used to regulate the flow rate of the gas being supplied into the drilling fluid, or it can be separate venturi or orifice plate.

Abstract: A method of processing seismic data, said seismic data having been obtained by: performing a plurality of sweeps, wherein each sweep comprises generating seismic signals in the earth using a plurality of vibrators by applying a pilot sweep wave-form to each vibrator, each pilot sweep being a waveform of changing frequency; measuring the force applied to the earth by each vibrator to determine a measured force waveform; and measuring the seismic signals at one or more locations remote from the vibrators; said method comprising: filtering the measured force waveform to remove harmonics of the pilot sweep and thus determining a filtered force waveform; generating an inversion operator from the filtered force waveform for each vibrator; and applying said inversion operator to the measured seismic signals to determine the contribution of each vibrator to the seismic signals.

Abstract: A system and method for attenuating noise in vibroseis data acquisition. In particular, according to the invention, several preferred methods are discloses that are particularly useful for attenuating noise in seismic data acquired by slip sweep vibroseis techniques. The techniques disclosed involve band-splitting in the time-frequency domain using mirror-filtering, such as a quadrature mirror filter. A noise estimate is made according to which the data is normalized and summed. The time frequency data then reconstructed and transformed back into time domain for further processing.

Abstract: A method of seismic exploration while drilling from within a borehole containing fluid, with a source and receivers positioned in the borehole is provided, comprising detecting small amplitude signals from waves within the fluid. The method is used to identify signals from waves within the fluid known as tube waves that result from compressional waves converted at the bottom of the borehole. The invention also includes seismic detection apparatus comprising ring hydrophones or similar pressure sensors. The apparatus is preferably attached to a coiled tubing with the drill bit actuated by a separate actuator as source.

Abstract: Methods and apparatus are described for seismic signal acquisition utilizing an odd number of vibratory sources arranged in line and positioning the sources for one sweep cycle at positions occupied by other sources during the previous sweep cycle. The method has advantages in particular for marine seismic acquisitions.

Abstract: Methods and apparatus are described for compressing seismic data. The data compression is achieved by splitting the data into subsets and applying requantization levels to those subsets which depend on a number representing the subset and on time. Further error criteria ensure that the error introduced by the data compression does not affect the data in a time window representing the listening time. The compression ratio can be improved by applying data encoding techniques to the subsets.