# US 2013/0158878 A1 · Device and method for locating microseismic events using array of receivers > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2013/0158878 A1 - Document ID: US20130158878A1 - Status: Published application - Kind: A1 - Application number: 13/530,307 - Filed: 2012-06-22 - Published: 2013-06-20 - Earliest claimed: 2011-12-15 - Assignees: Cggveritas Services SA - Inventors: Estelle REBEL; Julien MEUNIER - Web page: https://patentgrep.com/patent/US20130158878A1 ## CPC - G01V 1/282: {Application of seismic models, synthetic seismograms} - G01V 1/288: {Event detection in seismic signals, e.g. microseismics (G01V1/36 takes precedence)} - G01V 1/366: {by correlation of seismic signals} - G01V 2210/123: Passive source, e.g. microseismics - G01V 2210/55: Array focusing; Phased arrays - G01V 2210/65: Source localisation, e.g. faults, hypocenters or reservoirs - G01V: GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS (means for indicating the location of accidentally buried, e.g. snow-buried, persons A63B29/02) ## Abstract Device and method for locating a microseismic event taking place in a subsurface of the earth. The method includes receiving recorded seismic data S(t, Rc) acquired by a plurality of receivers as a function of time t and a position Rc; receiving a reference signal model SiMo(t, Rc) that corresponds to seismic data recorded by the plurality of receivers if an explosion occurs at an injection point in the subsurface; time correlating the recorded seismic data S(t, Rc) with the signal model SiMo(t, Rc) to determine correlated seismic data DMSS; calculating a detection curve for each of plural cells in a given volume in the subsurface of the earth based on the correlated seismic data DMSS; and determining a seismic location in the volume of the microseismic event based on a largest value of maximums of the detection curves calculated for various points of the given volume in the subsurface. ## Claims ### Claim 1 A method for locating a microseismic event taking place in a subsurface of the earth, the method comprising: receiving recorded seismic data S(t, Rc) acquired by a plurality of receivers as a function of time t and a position Rc; receiving a reference signal model SiMo(t, Rc) that corresponds to seismic data recorded by the plurality of receivers if an event occurs at an injection point in the subsurface; time correlating the recorded seismic data S(t, Rc) with the reference signal model SiMo(t, r) to determine correlated seismic data DMSS; calculating a detection curve for each of plural cells in a given volume in the subsurface of the earth based on the correlated seismic data DMSS; and determining a seismic location in the volume of the microseismic event based on a largest value of maximums of the detection curves calculated for various points of the given volume in the subsurface. ### Claim 2 (depends on 1) The method of claim 1, further comprising: calculating the detection curve for a single location in the given volume by summing correlated seismic data DMSS for a given vicinity V of a trace S(t, Rc) having the position Rc. ### Claim 3 (depends on 2) The method of claim 2, further comprising: calculating the detection curve for the various points in the given volume, the various points having corresponding locations. ### Claim 4 (depends on 3) The method of claim 3, further comprising: selecting the seismic location from the locations associated with the various points of the given volume such that the detection curve corresponding to the selected seismic location has a maximum peak larger than any maximum peak of the remaining detection curves corresponding to the plural locations of the given volume. ### Claim 5 (depends on 1) The method of claim 1, wherein the step of correlating comprises: calculating a correlation DM(t, Rc) of S(t, Rc) with SiMo(t, Rc); and calculating the correlated seismic data DMSSXCor0(t, Rc) as a multiplication between the correlation DM(t, Rc) and a sum of neighbor correlations DM(t, R), where the neighbor correlations are calculated in a vicinity V of the location Rc, wherein the vicinity V has the radius Rd and R is smaller than or equal to Rd. ### Claim 6 (depends on 1) The method of claim 1, further comprising: extrapolating the reference signal model SiMo(t, Rc) to other locations in the given volume to obtain an extrapolated signal model SiMoextrapolated(t, Rc). ### Claim 7 (depends on 6) The method of claim 6, further comprising: calculating the correlated seismic data DMSS for the extrapolated signal model SiMoextrapolated(t, Rc); calculating the detection curve based on the extrapolated signal model SiMoextrapolated(t, Rc); repeating the above calculations for the various point of the volume; and selecting the seismic location that corresponds to the extrapolated signal model SiMoextrapolated(t, Rc) that determines a constant arrival time of the maximum of the correlation between the recorded seismic data S(t, Rc) and the extrapolated signal model SiMoextrapolated(t, Rc). ### Claim 8 (depends on 7) The method of claim 7, wherein the extrapolated signal model SiMoextrapolated(t,) is determined by: SiMo extrapolated  ( t , Rc , Sg ) = SiMo  ( t , Rc ) × δ  ( t + d p  ( Rc ) - d Sg  ( Rc ) V rms ) with dp(Rc) being a distance between the injection point and the plurality receivers and dsg(Rc) is a distance between a location Sg and the plurality of receivers. ### Claim 9 (depends on 1) The method of claim 1, further comprising: assigning a focal mechanism to the microseismic event based on amplitude of the correlated seismic data DM(t, Rc). ### Claim 10 (depends on 9) The method of claim 9, further comprising: deriving a sign distribution of the amplitude of the correlated seismic data DM over the plurality of receivers; selecting a possible focal mechanism and correcting polarities of the signs based on the selected possible focal mechanism; summing up the polarities corrected correlated seismic data DM; repeating these steps for various focal mechanisms; and selecting the actual focal mechanism for which the summed up polarities corrected correlated seismic data DM is maximum. ### Claim 11 (depends on 9) The method of claim 9, further comprising: inverting an amplitude and a sign distribution of the correlated seismic data DM corresponding to the microseismic event to determine the focal mechanism. ### Claim 12 A device for locating a microseismic event taking place in a subsurface of the earth, the device comprising: an interface configured to receive recorded seismic data S(t, Rc) acquired by a plurality of receivers as a function of time t and a position Rc; and a processor connected to the interface and configured to, receive a reference signal model SiMo(t, Rc) that corresponds to seismic data recorded by the plurality of receivers if an explosion occurs at an injection point in the subsurface, time correlate the recorded seismic data S(t, Rc) with the reference signal model SiMo(t, Rc) to determine correlated seismic data DMSS, calculate a detection curve for each of plural cells in a given volume in the subsurface of the earth based on the correlated seismic data DMSS, and determine a seismic location in the volume of the microseismic event based on a largest value of maximums of the detection curves calculated for various points of the given volume in the subsurface. ### Claim 13 (depends on 12) The device of claim 12, wherein the processor is further configured to: calculate the detection curve for a single location in the given volume by summing correlated seismic data DMSS for a given vicinity V of a trace S(t, Rc) having the position Rc. ### Claim 14 (depends on 13) The device of claim 13, wherein the processor is further configured to: calculate the detection curve for the various points in the given volume, the various points having corresponding locations. ### Claim 15 (depends on 14) The device of claim 14, wherein the processor is further configured to: select the seismic location from the locations associated with the various points of the given volume such that the detection curve corresponding to the selected seismic location has a maximum peak larger than any maximum peak of the remaining detection curves corresponding to the plural locations of the given volume. ### Claim 16 (depends on 12) The device of claim 12, wherein the processor is further configured to: calculate a correlation DM(t, Rc) of S(t, Rc) with SiMo(t, Rc); and calculate the correlated seismic data DMSS(t, Rc) as a cross-correlation between the correlation DM(t, Rc) and a sum of neighbor correlations DM(t, R), where the neighbor correlations are calculated in a vicinity V of the location Rc, wherein the vicinity V has the radius Rd and R is smaller than or equal to Rd. ### Claim 17 (depends on 12) The device of claim 12, wherein the processor is further configured to: extrapolate the reference signal model SiMo(t, Rc) to other locations Sg in the given volume to obtain an extrapolated signal model SiMoextrapolated(t, Rc, Sg). ### Claim 18 (depends on 17) The device of claim 17, wherein the processor is further configured to: calculate the correlated seismic data DMSS for the extrapolated signal model SiMoextrapolated(t, Rc, Sg); calculate the detection curve based on the extrapolated signal model SiMoextrapolated(t, Rc, Sg); repeat the above calculations for the various point of the volume; and select the seismic location that corresponds to the extrapolated signal model SiMoextrapolated(t, Rc, Sg) that determines a constant arrival time of the maximum of the correlation between the recorded seismic data S(t, Rc) and the extrapolated signal model SiMoextrapolated(t, Rc, Sg). ### Claim 19 (depends on 18) The device of claim 18, wherein the extrapolated signal model SiMoextrapolated(t, Rc, Sg) is determined by: SiMo extrapolated  ( t , Rc , Sg ) = SiMo  ( t , Rc ) × δ  ( t + d p  ( Rc ) - d Sg  ( Rc ) V rms ) with dp(Rc) being a distance between the injection point and the plurality receivers and dSg(Rc) is a distance between a location Sg and the plurality of receivers. ### Claim 20 (depends on 12) The device of claim 12, wherein the processor is further configured to: assign a focal mechanism to the microseismic event based on an amplitude of the correlated seismic data DM(t, Rc). ### Claim 21 A computer readable medium including computer executable instructions, wherein the instructions, when executed, implement a method for locating a microseismic event taking place in a subsurface of the earth, the method comprising: receiving recorded seismic data S(t, Rc) acquired by a plurality of receivers as a function of time t and a position Rc; receiving a reference signal model SiMo(t, Rc) that corresponds to seismic data recorded by the plurality of receivers if an explosion occurs at an injection point in the subsurface; time correlating the recorded seismic data S(t, Rc) with the reference signal model SiMo(t, Rc) to determine correlated seismic data DMSS; calculating a detection curve for each of plural cells in a given volume in the subsurface of the earth based on the correlated seismic data DMSS; and determining a seismic location in the volume of the microseismic event based on a largest value of maximums of the detection curves calculated for various points of the given volume in the subsurface.