# US 2014/0156191 A1 · Method and system of using a data weighted electromagnetic source for time-lapse monitoring of a reservoir production or hydraulic fracturing > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2014/0156191 A1 - Document ID: US20140156191A1 - Status: Published application - Kind: A1 - Application number: 13/693,082 - Filed: 2012-12-04 - Published: 2014-06-05 - Earliest claimed: 2012-12-04 - Assignees: Chevron U.S.A. Inc. - Inventors: Gary Michael Hoversten; Vanessa Claire Brown; David Lee Alumbaugh - Web page: https://patentgrep.com/patent/US20140156191A1 ## CPC - G01V 3/12: operating with electromagnetic waves {(operating with millimetre waves G01V8/005)} - G01V 3/083: {Controlled source electromagnetic [CSEM] surveying} - G01V 3/38: Processing data, e.g. for analysis, for interpretation, for correction - G01V 2003/084: {Sources} - G01V 2003/086: {Processing} - 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 A system and a method for time lapse monitoring of a target feature within a rock formation are provided. The system includes a data weighted electromagnetic source configured to generate an electromagnetic field in vicinity or at a surface of the rock formation; and an electromagnetic receiver configured to measure a component of the electromagnetic field generated by the source. The data weighted electromagnetic source includes a plurality of electromagnetic sources and an electromagnetic field contribution from each electromagnetic source is weighted so as to enhance the component of the electromagnetic field measured by the electromagnetic receiver. ## Claims ### Claim 1 A system for time lapse monitoring of a target feature within a rock formation, the system comprising: a data weighted electromagnetic source configured to generate an electromagnetic field in vicinity or at a surface of the rock formation; and an electromagnetic receiver configured to measure a component of the electromagnetic field generated by the source, wherein the data weighted electromagnetic source includes a plurality of electromagnetic sources and an electromagnetic field contribution from each electromagnetic source is weighted so as to enhance the component of the electromagnetic field measured by the electromagnetic receiver. ### Claim 2 (depends on 1) The system according to claim 1, wherein amplitude, phase or both of each electromagnetic field generated by each of the plurality of electromagnetic sources is selected so as to enhance the component of the electromagnetic field measured by the electromagnetic receiver. ### Claim 3 (depends on 1) The system according to claim 1, wherein in-phase and out-of-phase of the imaginary part of each electromagnetic field generated by each of the plurality of electromagnetic sources is selected so as to enhance the component of the electromagnetic field measured by the electromagnetic receiver. ### Claim 4 (depends on 1) The system according to claim 1, further comprising a processor configured to calculate a difference between a component of electromagnetic field measured at a first point in time and a component of electromagnetic field measured at a second point in time after the first point in time to determine a change in a characteristic of the target feature within the rock formation. ### Claim 5 (depends on 4) The system according to claim 4, wherein the target feature includes an oil reservoir, a gas reservoir, or a fracture. ### Claim 6 (depends on 5) The system according to claim 5, wherein a change in the characteristic of the target feature includes a fluid volume change in the oil or gas reservoir from a before production or a before injection state to an after production or an after injection state or change of the fracture by hydro-fracturing from a before hydro-fracturing state to an after hydro-fracturing state. ### Claim 7 (depends on 1) The system according to claim 1, further comprising a processor configured to perform an inversion process on the component of the electromagnetic field measured by the electromagnetic receiver to obtain an enhanced image of the target feature. ### Claim 8 (depends on 7) The system according to claim 7, wherein the processor is configured to perform the inversion process by using a sampling based stochastic algorithm where the measured component of electromagnetic field is used in a likelihood function or a deterministic gradient based inversion algorithm where the measured component of electromagnetic field is used in an object function. ### Claim 9 (depends on 1) The system according to claim 1, wherein the plurality of electromagnetic sources include a plurality of electric dipole sources. ### Claim 10 (depends on 1) The system according to claim 1, wherein the plurality of electromagnetic sources include a plurality of magnetic field sources. ### Claim 11 (depends on 1) The system according to claim 1, wherein the electromagnetic receiver includes one or more electric field receivers. ### Claim 12 (depends on 1) The system according to claim 1, wherein the electromagnetic receiver includes one or more magnetic field receivers. ### Claim 13 (depends on 1) The system according to claim 1, wherein the electromagnetic receiver is configured to measure the component of the electromagnetic field before production or before injection in a reservoir or before hydro-fracturing the rock formation to obtain a first electromagnetic response, and to measure the component of the electromagnetic field after production, or after injection in the reservoir or after hydro-fracturing the rock formation to obtain a second electromagnetic response. ### Claim 14 (depends on 13) The system according to claim 13, wherein hydro-fracturing the rock formation includes injecting a conductive fluid into the rock formation to increase an electrical conductivity of the rock formation by displacing less conductive fluids that naturally exist within the rock formation. ### Claim 15 (depends on 13) The system according to claim 13, wherein hydro-fracturing the rock formation includes injecting a magnetically enhanced fluid into the rock formation to increase its magnetic susceptibility by displacing less susceptible material or fluids that naturally exist within the rock formation. ### Claim 16 (depends on 13) The system according to claim 13, further comprising a processor configured to compute a percent change from the first and second electromagnetic response. ### Claim 17 A method for time lapse monitoring of a target feature within a rock formation, the method comprising: generating an electromagnetic field in vicinity or at a surface of the rock formation using a data weighted electromagnetic source, the data weighted electromagnetic source including a plurality of electromagnetic sources; measuring a component of the electromagnetic field generated by the source using an electromagnetic receiver; and weighting an electromagnetic field contribution from each electromagnetic source so as to enhance the component of the electromagnetic field measured by the electromagnetic receiver. ### Claim 18 (depends on 17) The method according to claim 17, further comprising selecting amplitude, phase or both of each electromagnetic field generated by each of the plurality of electromagnetic sources so as to enhance the component of the electromagnetic field measured by the electromagnetic receiver. ### Claim 19 (depends on 17) The method according to claim 17, further comprising selecting in-phase and out-of-phase of the imaginary part of each electromagnetic field generated by each of the plurality of electromagnetic sources so as to enhance the component of the electromagnetic field measured by the electromagnetic receiver. ### Claim 20 (depends on 17) The method according to claim 17, further comprising calculating a difference between a component of electromagnetic field measured at a first point in time and a component of electromagnetic field measured at a second point in time after the first point in time to determine a change in a characteristic of the target feature within the rock formation. ### Claim 21 (depends on 20) The method according to claim 20, wherein the target feature includes an oil reservoir, a gas reservoir, or a fracture. ### Claim 22 (depends on 21) The method according to claim 21, wherein determining the change in the characteristic of the target feature includes determining a fluid volume change in the oil or gas reservoir from a before production or a before injection state to an after production or an after injection state or change of the fracture by hydro-fracturing from a before hydro-fracturing state to an after hydro-fracturing state. ### Claim 23 (depends on 17) The method according to claim 17, further comprising performing an inversion process on the component of the electromagnetic field measured by the electromagnetic receiver to obtain an enhanced image of the target feature. ### Claim 24 (depends on 23) The method according to claim 23, wherein performing the inversion process comprises performing the inversion process by using a sampling based stochastic algorithm where the measured component of electromagnetic field is used in a likelihood function or a deterministic gradient based inversion algorithm where the measured component of electromagnetic field is used in an object function. ### Claim 25 (depends on 17) The method according to claim 17, wherein the plurality of electromagnetic sources include a plurality of electric dipole sources. ### Claim 26 (depends on 17) The method according to claim 17, wherein the plurality of electromagnetic sources include a plurality of magnetic field sources. ### Claim 27 (depends on 17) The method according to claim 17, wherein the electromagnetic receiver includes one or more electric field receivers. ### Claim 28 (depends on 17) The method according to claim 17, wherein the electromagnetic receiver includes one or more magnetic field receivers. ### Claim 29 (depends on 17) The method according to claim 17, wherein measuring by the electromagnetic receiver comprises measuring the component of the electromagnetic field before production or before injection in a reservoir or before hydro-fracturing the rock formation to obtain a first electromagnetic response, and measuring the component of the electromagnetic field after production, or after injection in the reservoir or after hydro-fracturing the rock formation to obtain a second electromagnetic response. ### Claim 30 (depends on 29) The method according to claim 29, wherein hydro-fracturing the rock formation includes injecting a conductive fluid into the rock formation to increase an electrical conductivity of the rock formation by displacing less conductive fluids that naturally exist within the rock formation. ### Claim 31 (depends on 29) The method according to claim 29, wherein hydro-fracturing the rock formation includes injecting a magnetically enhanced fluid into the rock formation to increase its magnetic susceptibility by displacing less susceptible material or fluids that naturally exist within the rock formation. ### Claim 32 (depends on 29) The method according to claim 29, further comprising computing a percent change from the first and second electromagnetic response. ### Claim 33 A method for time lapse monitoring of a target feature within a rock formation, the method comprising: generating a starting model for time lapse monitoring from initial data prior to a start of time lapse; calculating a response of the starting model using a numerical algorithm; creating one or more scenario models that hypothesize how subsurface electromagnetic properties will be changing over time; calculating a response of the one or more scenario models using the same numerical algorithm applied in calculating the response of the starting model; calculating an optimal set of data weighted electromagnetic source parameters that maximize a difference between the response of the starting model and the response of the one or more scenario models; analyzing a real time lapse data set by applying the calculated optimal set of synthetic parameters to the real time lapse data set; and calculating a difference between the real time lapse data set and the initial data set. ### Claim 34 (depends on 33) The method according to claim 33, wherein the data weighted electromagnetic source parameters include amplitude, a phase or both of the electromagnetic field or in-phase and out-of-phase components of the imaginary part of the electromagnetic field.