Method to determine a time-depth model

A non-transitory computer-readable memory having computer-executable instructions stored thereon that, when executed by a computer processor, perform steps comprising:

• receiving a time-domain surface seismic dataset for a subterranean region of interest;
• for each drilling depth among a sequence of drilling depths in order:
• receiving a seismic dataset comprising a plurality of seismic traces generated by a drill bit drilling a wellbore to each drilling depth within the subterranean region of interest,
• wherein the sequence of drilling depths is arranged in order of increasing depth along the wellbore;
• wherein the wellbore follows a wellbore path;
• wherein an orientation of the drill bit is based on the wellbore path;
• and
• wherein each of the plurality of seismic traces is recorded by each of a plurality of seismic receivers,
• determining, using the seismic dataset, a range of seismic velocities, a range of vertical traveltimes, and a geological model, a coherency map comprising a plurality of positions,
• wherein each position on the coherency map corresponds to a seismic velocity among the range of seismic velocities and a vertical traveltime among the range of vertical traveltimes;
• and
• wherein each position on the coherency map represents a measure of similarity within the plurality of seismic traces corrected using the seismic velocity, the vertical traveltime, and the geological model,
• determining a locus from the coherency map,
• wherein the locus comprises a plurality of extremums of the measure of similarity;
• and
• wherein the locus corresponds to seismic velocities among the range of seismic velocities as a function of vertical traveltimes among the range of vertical traveltimes,
• forming an objective function based on the locus and a measured depth interval,
• wherein the measured depth interval comprises a difference between two drilling depths among the sequence of drilling depths,
• determining a unique seismic velocity among the seismic velocities and a unique vertical traveltime among the vertical traveltimes based on an extremum of the objective function,
• generating an updated vertical traveltime, depth model using the unique seismic velocity for at least two drilling depths among the sequence of drilling depths, the unique vertical traveltime for the at least two drilling depths, and the at least two drilling depths,
• determining a depth-domain surface seismic dataset using the time-domain surface seismic dataset and the updated vertical traveltime, depth model,
• revising the wellbore path based on the depth-domain surface seismic dataset, and
• revising the orientation of the drill bit based on the revised wellbore path.

A system comprising:

• a computer processor configured to receive a time-domain surface seismic dataset for a subterranean region of interest;
• for each drilling depth among a sequence of drilling depths in order:
• a drilling system comprising a drill bit and configured to drill, using the drill bit, a wellbore to each drilling depth within the subterranean region of interest,
• wherein the sequence of drilling depths is arranged in order of increasing depth along the wellbore,
• wherein the wellbore follows a wellbore path, and
• wherein an orientation of the drill bit is based on the wellbore path,
• a plurality of seismic receivers configured to record a seismic dataset comprising a plurality of seismic traces generated by the drill bit,
• wherein the computer processor is further configured to:
• receive, from the plurality of seismic receivers, the seismic dataset;
• determine, using the seismic dataset, a range of seismic velocities, a range of vertical traveltimes, and a geological model, a coherency map comprising a plurality of positions,
• wherein each position on the coherency map corresponds to a seismic velocity among the range of seismic velocities and a vertical traveltime among the range of vertical traveltimes, and
• wherein each position on the coherency map represents a measure of similarity within the plurality of seismic traces corrected using the seismic velocity, the vertical traveltime, and the geological model;
• determine a locus from the coherency map,
• wherein the locus comprises a plurality of extremums of the measure of similarity, and
• wherein the locus corresponds to seismic velocities among the range of seismic velocities as a function of vertical traveltimes among the range of vertical traveltimes;
• form an objective function based on the locus and a measured depth interval,
• wherein the measured depth interval comprises a difference between two drilling depths among the sequence of drilling depths;
• determine a unique seismic velocity among the seismic velocities and a unique vertical traveltime among the vertical traveltimes based on an extremum of the objective function;
• generate an updated vertical traveltime, depth model using the unique seismic velocity for at least two drilling depths among the sequence of drilling depths, the unique vertical traveltime for the at least two drilling depths, and the at least two drilling depths;
• determine a depth-domain surface seismic dataset using the time-domain surface seismic dataset and the vertical traveltime, depth model;
• and
• revise the wellbore path based on the depth-domain surface seismic dataset;
• wherein the drilling system is further configured to revise the orientation of the drill bit based on the revised wellbore path.