SYSTEM AND METHOD FOR DETERMINING EARTH FRACTURE PROPAGATION

Hydraulic fracture extension in earth formation zones of interest may be monitored by placing one or more monitor wells in predetermined positions on opposite sides of an azimuth aligned with the expected fracture plane extending from a fluid waste injection well. The monitor wells are provided with arrays of vertically spaced triaxial geophone units and the signals from the geophones are transmitted to a central processing unit for treatment and analysis to determine the location of micro-earthquake events which occur as the fracture propagates radially and, usually, vertically away from the injection well. Geophone signals are converted to digital format and selectively stored on magnetic tapes or in a shared memory of a central processing unit which is operable to display selected channels for geophone signals in a way so that minimum arrival time of a signal at a particular geophone will indicate the growth of the fracture in real time to control fluid waste disposal, for example. The converted data may be selectively screened by a program which eliminates weak or spurious signals and the screened signals may then be analyzed by a location routine and displayed in a manner which indicates the location of the detected and screened events with respect to the injection well.