System for generating velocity models of subsalt formations

A system for creating a three-dimensional velocity model of a subterranean formation below a surface comprising:

• a. a transmitter configured to transmit a signal into the subterranean formation,
• i. wherein the subterranean formation has a first zone above a second zone,
• ii. wherein the second zone is above a basement,
• iii. wherein the second zone has a lower seismic propagation velocity than the first zone,
• iv. wherein the first zone has a lower seismic propagation velocity than the basement,
• v. wherein the signal causes seismic waves to travel into the subterranean formation, and
• vi. wherein refraction of the seismic waves by the basement causes at least one of the seismic waves to be conveyed through the second zone and the first zone;
• b. a plurality of dispersed receiver nodes located on a surface above the subterranean formation,
• i. wherein the plurality of nodes is configured to receive the refracted seismic waves and output a node signal based on the received refracted seismic waves;
• and
• c. a computer in communication with the plurality of dispersed receiver nodes to receive the output node signal, the computer including at least one processor and at least one memory, the memory comprising a plurality of non-transitory executable instructions that, when executed, cause the at least one processor to
• i. determine velocities of refracted seismic waves based, at least in part, on the output node signal, and
• ii. generate a three-dimensional velocity model of the subterranean formation, based, at least in part, on an inversion and the velocities of the refracted seismic waves.

A method of creating a three-dimensional velocity model of a subterranean formation below an ocean floor comprising:

• a. controlling at least one seismic source to emit a plurality of seismic waves into the subterranean formation,
• i. wherein the subterranean formation comprises a salt formation above a sediment layer,
• ii. wherein the sediment layer is above a basement,
• iii. wherein the seismic waves are refracted by the subterranean formation to cause refracted seismic waves,
• iv. wherein refraction of the seismic waves by the basement causes at least one of the seismic waves to be conveyed through the subterranean formation such that it travels through the sediment layer and the salt formation;
• b. receiving signals from a seismic recording system that is disposed on a surface of the earth,
• i. wherein the seismic recording system comprises a plurality of nodes,
• ii. wherein the seismic recording system is configured to receive the refracted seismic waves and output a signal based on the received refracted seismic waves,
• c. recording data about the refracted seismic waves using, at least in part, the received signal from the seismic recording system;
• d. determining velocities of the refracted seismic waves based, at least in part, on the recorded data about the refracted seismic waves;
• and
• e. converting the determined velocities of the refracted seismic waves into a three-dimensional velocity model of the subterranean formation.