We describe a technique for performing optimal, least-squares deconvolution of vertical seismic profile (VSP) data. The method is a two-step process that involves (1) estimating the source signature and (2) applying a least-squares optimum deconvolution operator that minimizes the noise not coherent with the source signature estimate. The optimum inverse problem, formulated in the frequency domain, gives as a solution an operator that can be interpreted as a simple inverse to the estimated aligned signature multiplied by semblance across the array. An application to a zero-offset VSP acquired with a dynamite source shows the effectiveness of the operator in attaining the two conflicting goals of adaptively spiking the effective source signature and minimizing the noise. Signature design for seismic surveys could benefit from observing that the optimum deconvolution operator gives a flat signal spectrum if and only if the seismic source has the same amplitude spectrum as the noise.

We describe a method for extracting and deconvolving a signal generated by a drill bit and collected by an array of surface geophones. The drill-noise signature is reduced to an effective impulse by means of a multichannel Wiener deconvolution technique, producing a walk-away reverse vertical seismic profile (VSP) sampled almost continuously in depth. We show how the multichannel technique accounts for noise and for internal drill-string reflections, automatically limiting the deconvolved data to frequencies containing significant energy.We have acquired and processed a data set from a well in Germany while drilling at a depth of almost 4000m. The subsurface image derived from these data compares well with corresponding images from a 3-D surface seismic survey, a zero-offset VSP survey, and a walk-away VSP survey acquired using conventional wireline techniques. The effective bandwidth of the deconvolved drill-noise data is comparable to the bandwidth of surface seismic data but significantly smaller than what can be achieved with wireline VSP techniques.Although the processing algorithm does not require the use of sensors mounted on the drill string, these sensors provide a very economic way to compress the data. The sensors on the drill string were also used for accurate timing of the deconvolved drill-noise data.

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We have developed a method for finding microseismic hypocenters from data recorded by arrays of triaxial motion sensors. The method reconstructs the elastic time-series signatures for possible microseismic sources at any point in 3D space, using full-waveform migration of the recorded vector wavefield. The imaging condition for the migration is based on a semblance-weighted deconvolution between two or more reconstructed source signatures, requiring similarity and simultaneity of the reconstructed signatures. This imaging condition eliminates the need for an absolute timing of the data, gives optimum resolution for the location of the microseismic sources—better than correlation-based approaches—and ensures numerical stability by adapting to the signal and noise conditions of the data. Because the method eliminates time-consuming phase picking and traditional event association, it should be well suited for fully or semiautomated data processing. The method was tested by an application to field data acquired with arrays of three-component receivers in two deep wells. Nevertheless, the formulation is equally applicable to data acquired by a distribution of single three-component receivers, or local arrays of these, deployed at the surface or in one or several shallow wells.

S U M M A R YWe investigate the applicability of an array-conditioned deconvolution technique, developed for analysing borehole seismic exploration data, to teleseismic receiver functions and data pre-processing steps for scattered wavefield imaging. This multichannel deconvolution technique constructs an approximate inverse filter to the estimated source signature by solving an overdetermined set of deconvolution equations, using an array of receivers detecting a common source. We find that this technique improves the efficiency and automation of receiver function calculation and data pre-processing workflow. We apply this technique to synthetic experiments and to teleseismic data recorded in a dense array in northern Canada. Our results show that this optimal deconvolution automatically determines and subsequently attenuates the noise from data, enhancing P-to-S converted phases in seismograms with various noise levels. In this context, the array-conditioned deconvolution presents a new, effective and automatic means for processing large amounts of array data, as it does not require any ad-hoc regularization; the regularization is achieved naturally by using the noise present in the array itself.

We have determined how the measured polarization and traveltime for P- and S-waves can be used directly with vertical seismic profile data for estimating the salt exit points in a salt-proximity survey. As with interferometry, the processes described use only local velocities. For the data analyzed in this paper, our procedures have confirmed the location, inferred from surface-seismic data, of the flank of a steeply dipping salt body near the well. This has provided us more confidence in the estimated reservoir extent moving toward the salt face, which in turn has added critical information for the economic evaluation of a possible new well into the reservoir. We also have found that ray-based vector migration, based on the assumptions of locally plane wavefronts and locally plane formation interfaces, can be used to create 3D reflection images of steeply dipping sediments near the well, again using only local velocities. Our local reflection images have helped confirm the dips of the sediments between the well and the salt flank. Because all parameters used in these processes are local and can be extracted from the data themselves, the processes can be considered to be self-sufficient.

We describe a new optical three-component accelerometer for borehole applications. Field data acquired in early 2020 in a fiber-optic-instrumented well in Houston, Texas, show that the new optical accelerometer is a viable borehole seismic sensor, measuring signals at frequencies from subhertz to hundreds of hertz. It is argued that an array of these sensors could be used to complement distributed acoustic sensing (DAS) technology to compensate for the inability of DAS sensors to measure wavefield polarization. This hybrid fiber-optic receiver array would be a fully optical wide-bandwidth sensor array without any electronics in the well. With a maximum operational temperature expected to exceed 200°C, this array would not be affected significantly by possible high temperatures in the near-reservoir section of the well.

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