method and arrangement for detection and automatic classification of underground seismic events after at least one selection criterion

摘要

Seismic signals above a certain threshold (Sd) are identified on a trace during a detection window (Pld) for at least one criterion relative to a defined selection function. A global recording level (Ple) surrounding the detection window is selected on the trace and signals in this recording level are labelled to show whether they are purely seismic, or are linked in some way to artefacts. ??Automatic classification according to different criteria of events detected on traces corresponding to seismic or acoustic signals measured by detectors coupled with an underground formation, whether the events are purely seismic or microseismic in nature or depend in part on artefacts connected to the external environment or exploitation or monitoring activities, and selecting the significant parts of the traces at the end of analysis. The selection criteria comprises the identification of events on a single recording trace (or on p (p)=2) different traces if the corresponding detection levels are contained in a defined time lapse) and memorization of the corresponding global recording levels on several traces (at least the p different traces, preferably more). One of the traces produced by collecting signals due to artefacts includes application of a canceling criterion including classification of the other traces where events are detected in the category of cancelled traces and their memorization. Traces in which the detection time is greater than a defined time interval are inhibited and eventually revalidated if the selection function value drops below a second threshold n a reactivation level. The traces are obtained using seismic or acoustic detectors coupled to formations around a well through an underground formation. Several selection criteria are used from a library of criteria. The recorded traces are signals returned by the formation in response to signals emitted in the ground from a seismic source and the inhibition criteria are used on several traces to ensure only the seismic events not provoked by this source are selected. ??An Independent claim is also included for a device for treating data to automatically classify it according to several criteria as above , and a seismic monitoring device incorporating such a data treatment device. The detectors are hydrophones or geophones and are coupled to the formation by a liquid or cement, by mechanical means or by magnets.