# US 11,029,440 B2 · Methods and systems with estimated synchronization between modular downhole logging system modules > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,029,440 B2 - Document ID: US11029440B2 - Status: Granted - Kind: B2 - Application number: 16/617,977 - Filed: 2017-06-27 - Published: 2020-06-04 - Granted: 2021-06-08 - Earliest claimed: 2017-06-27 - Assignees: Halliburton Energy Services, Inc. - Applicants: Halliburton Energy Services, Inc. - Inventors: Hsu-Hsiang Wu; Matthew Chase Griffing; Christopher Golla - Web page: https://patentgrep.com/patent/US11029440B2 ## CPC - G01V 1/48: Processing data - G01V 3/30: operating with electromagnetic waves - E21B 47/13: by electromagnetic energy, e.g. radio frequency - E21B 47/26: Storing data down-hole, e.g. in a memory or on a record carrier - G01V 1/40: specially adapted for well-logging - G01V 3/18: specially adapted for well-logging - G01V 3/38: Processing data, e.g. for analysis, for interpretation, for correction - G01V 1/26: Reference-signal-transmitting devices, e.g. indicating moment of firing of shot - G01V 2200/16: Measure-while-drilling or logging-while-drilling - G01V 2210/1214: Continuous - G01V 2210/43: Spectral - G01V: GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS (means for indicating the location of accidentally buried, e.g. snow-buried, persons A63B29/02) - E21B: EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS ## Abstract A modular downhole logging system includes a transmitter module having a local frequency, wherein the transmitter module transmits interrogation signals into a formation based on the local frequency. The downhole system also includes a receiver module axially-spaced from the transmitter module and that receives response signals corresponding to the interrogation signals, wherein the receiver module includes sampling logic and sync estimation logic. The sync estimation logic is configured to perform sync estimation operations including estimating the local frequency of the transmitter module based on analysis of response signal Fourier transform results corresponding to different frequencies. The sampling logic/clock is configured to sample the response signals based on the estimated local frequency of the transmitter module, wherein a processor derives formation property values using the sampled response signals. ## Claims ### Claim 1 A modular downhole logging system that comprises: a transmitter module having a local frequency, wherein the transmitter module transmits interrogation signals into a formation based on the local frequency; and a receiver module axially-spaced from the transmitter module and that receives response signals corresponding to the interrogation signals, wherein the receiver module includes sampling logic and sync estimation logic, wherein the sync estimation logic is configured to perform sync estimation operations including estimating the local frequency of the transmitter module based on analysis of response signal Fourier transform results corresponding to different frequencies, and wherein the sampling logic is configured to sample the response signals based on the estimated local frequency of the transmitter module, wherein a processor derives formation property values using the sampled response signals. ### Claim 2 (depends on 1) The modular downhole logging system of claim 1, wherein the sync estimation operations include determining response signal ratios to account for phase offset, wherein the processor derives formation property values using the response signal ratios. ### Claim 3 (depends on 1) The modular downhole logging system of claim 1, wherein the sync estimation operations include normalizing response signals based on a predetermined transmitter current to account for phase offset, wherein the processor derives formation property values using the normalized response signals. ### Claim 4 (depends on 1) The modular downhole logging system of claim 1, further comprising at least one additional receiver module, wherein the sync estimation operations are performed when response signals are received by two receiver modules with synchronized phase with respect to the transmitter module. ### Claim 5 (depends on 1) The modular downhole logging system of claim 1, further comprising at least one additional transmitter module, wherein the sync estimation operations are performed when response signals corresponding to two transmitter modules with synchronized phase are received by the receiver module. ### Claim 6 (depends on 1) The modular downhole logging system of claim 1, wherein the sync estimation operations are performed when response signals corresponding to interrogation signals initiated by the transmitter module at different times, depths, or azimuthal angles are received by the receiver module. ### Claim 7 (depends on 1) The modular downhole logging system of claim 1, wherein the transmitter module and the receiver module are components of a drillstring that performs logging-while-drilling (LWD) operations while deployed in a borehole. ### Claim 8 (depends on 1) The downhole system of claim 1, wherein the transmitter module and the receiver module are components of a tool string deployed in an open borehole via wireline, slickline, coiled tubing, or tubular string. ### Claim 9 (depends on 1) The modular downhole logging system of claim 1, wherein the transmitter module and the receiver module are components of a tool string deployed within a casing string installed in a borehole, wherein the tool string is deployed via wireline, slickline, coiled tubing, or tubular string. ### Claim 10 (depends on 1) The modular downhole logging system according to claim 1, wherein the transmitter module is part of a first downhole sub and the receiver module is part of a second downhole sub. ### Claim 11 (depends on 10) The modular downhole logging system of claim 10, wherein the first downhole sub and second downhole sub are coupled through one or more intervening downhole subs. ### Claim 12 A method that comprises: deploying a modular downhole logging system in a borehole, the modular downhole logging system having at least one transmitter module, at least one receiver module, and a processor; transmitting, by the at least one transmitter module, interrogation signals into a formation surrounding the borehole, wherein the interrogation signals are a function of a local frequency of the at least one transmitter module; receiving, by the at least one receiver module axially-spaced from the at least one transmitter module, response signals corresponding to the interrogation signals; performing sync estimation operations, by the at least one receiver module, wherein the sync estimation operations include estimating the local frequency of the at least one transmitter module based on analysis of response signal Fourier transform results corresponding to different frequencies; sampling, by the at least one receiver module, at least some of the response signals based on the estimated local frequency of the at least one transmitter module; and deriving, by the processor, formation property values using the sampled response signals. ### Claim 13 (depends on 12) The method of claim 12, wherein the sync estimation operations include determining response signal ratios that account for phase offset, wherein said deriving is based at least in part on the response signal ratios. ### Claim 14 (depends on 12) The method of claim 12, wherein the sync estimation operations include normalizing the response signals based on a predetermined transmitter current logic to account for phase offset, wherein said deriving is based at least in part on the normalized response signals. ### Claim 15 (depends on 12) The method of claim 12, wherein the sync estimation operations are performed when response signals are received by two receiver modules with synchronized phase with respect to a given transmitter module. ### Claim 16 (depends on 12) The method of claim 12, wherein the sync estimation operations are performed when response signals corresponding to two transmitter modules with synchronized phase are received by a receiver module. ### Claim 17 (depends on 12) The method of claim 12, wherein the sync estimation operations are performed when response signals corresponding to interrogation signals initiated by a given transmitter module at different times, depths, or azimuthal angles are received by a given receiver module. ### Claim 18 (depends on 12) The method of claim 12, wherein deploying the modular downhole logging system comprises lowering a drillstring with the modular downhole logging system into the borehole. ### Claim 19 (depends on 12) The method of claim 12, wherein deploying the modular downhole logging system comprises using a wireline, slick line, coiled tubing, or tubing string to lower a tool string with the modular downhole logging system into the borehole. ### Claim 20 (depends on 12) The method according to claim 12, wherein the at least one transmitter module and the at least one receiver module are distributed across a plurality of downhole subs of the modular downhole logging system.