Seismic data processing method for resolving the near-surface in the presence of velocity inversions
A method for weathered layer correction of seismic data includes identifying arrival times in the seismic data corresponding to a weathered layer velocity gradient. A velocity model of the weathered layer is generated using the arrival times. The seismic data are time adjusted using the velocity model.
1 . A method for weathered layer correction of seismic data, comprising:
identifying arrival times in the seismic data corresponding to a velocity gradient in a weathered layer, the seismic data comprising signals detected by a plurality of seismic sensors disposed in a selected pattern above an area of subsurface to be evaluated;
the arrival times corresponding to events having monotonically increasing velocity with respect to depth, the arrival times being greater than events having linear moveout with respect to offset;
generating a velocity model of the weathered layer using the arrival times; and
time adjusting the seismic data using the velocity model.
2 . The method of claim 1 wherein the identifying arrivals comprises arranging the seismic data into a common shot gather, a common receiver gather or a common midpoint gather.
3 . The method of claim 2 further comprising applying linear moveout to the common shot or common receiver or common midpoint gather.
4 . The method of claim 2 further comprising applying moveout to a common shot gather, a common receiver or a common midpoint gather to substantially flatten turning ray arrival times.
5 . The method of claim 1 wherein the generating a velocity model comprises applying turning ray tomography to the arrival times.
6 . The method of claim 1 further comprising using the generated velocity model in subsequent seismic processing.
7 . The method of claim 6 wherein the subsequent seismic processing comprises at least one of pre-stack depth migration and full waveform inversion.
8 . A computer program stored in a non-transitory computer readable medium, the program comprising logic operable to cause a programmable computer to perform acts comprising:
accepting as input to the computer signals detected by a plurality of seismic sensors disposed in a selected pattern above an area of subsurface to be evaluated;
in the computer, identifying arrival times in the seismic signals corresponding to a velocity gradient in a weathered layer, the arrival times corresponding to events having monotonically increasing velocity with respect to depth, the arrival times being greater than events having linear moveout with respect to offset;
in the computer, generating a velocity model of the weathered layer using the arrival times; and
in the computer, time adjusting the seismic signals using the velocity model.
9 . The computer program of claim 8 wherein the identifying arrivals comprises arranging the seismic data into a common shot gather, a common receiver gather or a common midpoint gather.
10 . The computer program of claim 9 further comprising applying linear moveout to the common shot or common receiver or common midpoint gather.
11 . The computer program of claim 9 further comprising applying moveout to a common shot gather, a common receiver or a common midpoint gather to substantially flatten turning ray arrival times.
12 . The computer program of claim 8 wherein the generating a velocity model comprises applying turning ray tomography to the arrival times.
13 . The computer program of claim 8 further comprising using the generated velocity model in subsequent seismic processing.
14 . The computer program of claim 13 wherein the subsequent seismic processing comprises at least one of pre-stack depth migration and full waveform inversion.
15 . A method for seismic surveying, comprising:
deploying a plurality of seismic sensors in a selected pattern above an area of subsurface to be evaluated;
actuating a seismic energy source;
detecting seismic energy at each of the plurality of seismic sensors in response to energy imparted into the areas of the subsurface by the seismic energy source;
in signals generated by the plurality of seismic sensors in response to the detected seismic energy, identifying arrival times in the seismic data corresponding to a weathered layer velocity gradient, the arrival times corresponding to events having monotonically increasing velocity with respect to depth, the arrival times being greater than events having linear moveout with respect to offset;
generating a velocity model of the weathered layer using the arrival times; and
time adjusting the seismic data using the velocity model.
16 . The method of claim 15 wherein the identifying arrivals comprises arranging the seismic data into a common shot gather, a common receiver gather or a common midpoint gather.
17 . The method of claim 16 further comprising applying linear moveout to the common shot or common receiver or common midpoint gather.
18 . The method of claim 16 further comprising applying moveout to a common shot gather, a common receiver or a common midpoint gather to substantially flatten turning ray arrival times.
19 . The method of claim 15 wherein the generating a velocity model comprises applying turning ray tomography to the arrival times.
20 . The method of claim 15 further comprising using the generated velocity model in subsequent seismic processing.
21 . The method of claim 20 wherein the subsequent seismic processing comprises at least one of pre-stack depth migration and full waveform inversion.