Method for monitoring a multi-layered system
View Patent ↗A method for monitoring a multi-layered system below a surface comprising a slow layer and a fast layer; the method comprising: transmitting one or more seismic waves from one or more seismic sources through the multi-layered system; receiving signals emanating from the multi-layered system in response to the one or more seismic waves with one or more receivers located a distance from the one or more seismic sources; identifying one or more critically refracted compressional (CRC) waves amongst the signals; and inferring information about a change in the slow layer based on the one or more CRC waves; wherein the CRC wave is a refracted wave which has traveled along an interface between the fast layer and an adjacent layer.
1. A method for monitoring a multi-layered system in a subsurface formation that includes a slow layer and a fast layer; the method comprising:
a) providing a set of signals obtained by:
i) transmitting one or more seismic waves from one or more seismic sources through the multi-layered system; and
ii) receiving signals emanating from the multi-layered system in response to the one or more seismic waves with one or more receivers located a distance from the one or more seismic sources;
wherein at least one of said seismic sources and receivers is in a well;
b) identifying among the received signals at least one critically refracted compressional (CRC) wave that has traveled along an interface between the fast layer and an adjacent layer;
c) performing steps a) and b) in a time-lapse mode so as to obtain at least two CRC waves;
d) inferring information about a change in the slow layer based on the at least two CRC waves; and
e) imaging the information from step d).
2. The method of claim 1 wherein the adjacent layer is the slow layer.
3. The method of claim 1 , further comprising:
f) performing a source and/or receiver redatumming of the CRC waves to the slow layer.
4. The method of claim 1 wherein the change in the slow layer comprises a movement of steam, heat pressure, fracturing, temperature, oil saturation, gas saturation, or chemicals within the slow layer.
5. The method of claim 1 wherein the one or more seismic sources are located in a first well traversing the multi-layered system.
6. The method of claim 5 wherein the one or more receivers are an array of geophones or hydrophones.
7. The method of claim 5 wherein the one or more receivers are located in a second well traversing a portion the multi-layered system.
8. The method of claim 7 wherein the first well and second well are located offshore.
9. The method of claim 5 wherein the one or more receivers are located on the surface.
10. The method of claim 1 wherein the one or more seismic sources are located on the surface.