The tunnel boring machine (TBM) is used extensively to mechanically excavate tunnels. To optimize the mechanical drilling and work safely, an estimate of the geology to be drilled is necessary. We consider using the elastic waves produced by the TBM cutting wheel to obtain seismic-while-drilling (SWD) information for predicting the geology ahead of the drilling front. This method uses accelerometers mounted on the TBM together with geophones located along and outside the tunnel, similar to the technique successfully used to drill oil and geothermal wells. Study of noise and the resolution of the signal produced by the large-diameter cutting head shows that nonstationary noise separation can be achieved by locating sensors at the front and rear ends of the tunnel. The (higher) resolution in front of the TBM is limited by pilot delays, while the (lower) lateral resolution is limited by the radial dimension of the TBM. Analysis of seismic data acquired in a field test shows that P- and S-wave arrivals have a wide frequency band and high amplitude in seismic traces measured 700 m away from the drilling front. In comparison with SWD applications in wells, tunnel SWD technology has the advantage of allowing direct access to the tunnel front, which makes it easy to connect the TBM reference sensors for while-drilling monitoring. This method can be successfully applied without interfering with drilling activity to monitor tunnel excavation continuously, reduce risks, and optimize drilling.

Seismic‐while‐drilling by using tunnel boring machine noise

The present invention provides a method and apparatus for logging an earth formation and acquiring subsurface information wherein a logging tool is conveyed in borehole to obtain parameters of interest. The parameters of interest obtained may be density, acoustic, magnetic or electrical values as known in the art. The parameters of interest may be transmitted to the surface at a plurality of resolutions using a multi-resolution image compression method. Parameters of interest are formed into a plurality of Cost Functions from which Regions of Interest are determined to resolve characteristics of the Features of interest within the Regions. Feature characteristics may be determined to obtain time or depth positions of bed boundaries and borehole Dip Angle relative to subsurface structures, as well borehole and subsurface structure orientation. Characteristics of the Features include time, depth, and geometries of the subsurface such as structural dip, thickness, and lithologies.

Apparent dip angle calculation and image compression based on region of interest

Wavelets in Petroleum Industry: Past, Present and Future

Multi-scale analysis of well-logging data in petrophysical and stratigraphic correlation ; Multi-scale analysis of well-logging data in petrophysical and stratigraphic correlation

Seismic-while-drilling services efficiently support drilling decisions. They use the vibrations produced by the drill-bit during perforation as a downhole seismic source. The seismic signal is recorded by sensors on the surface, and it is processed in order to obtain/update an image of the subsurface around the borehole. To improve the characterization of the source, some sensors have been experimentally installed also downhole, on the drill pipes in close proximity to the bit: data logged downhole have been able to give better quality information. Currently, the main drawback of downhole equipment is the absence of a high-bit-rate telemetry system to enable real-time activities. This problem may be solved by employing either an offline solution, with limited memory capacity up to few hundreds of megabytes, or an online solution with telemetry at a very low bit-rate (few bits per second). However, following the offline approach with standard acquisition parameters, the internal storage memory would be filled up in just a few hours at high acquisition rates. On the contrary, with the online solution, only a small portion of the acquired signals (or only alarm information about potentially dangerous events) can be transmitted in real time to the surface by using conventional mud-pulse telemetry. We present a lossy data compression algorithm based on a new representation of downhole data in angle domain, which is suitable for downhole implementation and may be successfully applied to both online and offline solutions. Numerical tests based on real field data achieve compression ratios up to 112:1 without major loss of information. This allows a significant increase in downhole time acquisition and in real-time information that can be transmitted through mud-pulse telemetry.

Efficient data compression for seismic-while-drilling applications

Compression of Downhole Data

The extension of the seismic-while-drilling tool includes the use of PDC bit signals both for seismic and drilling diagnostic purposes.

SWD Surface and Downhole Pilot Recording to Improve PDC Bit Signals

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Compression of Downhole Data

SWD Surface and Downhole Pilot Recording to Improve PDC Bit Signals