A shooting and receiving interchanging layout for crosswell seismic survey

For a conventional layout of a crosswell seismic survey, a downhole source and a receiver array are set in two wells respectively. A massive data set, in general, is acquired for velocity tomography and reflection imaging. We found that this conventional layout used in some areas in China led to some problems whether technically or economically making such surveys unattainable. In order to improve the situation, we propose a new observation configuration for crosswell seismic surveys which is titled “A shooting and receiving interchanging layout”. The principle of the method is from the imaging of offset VSP. When a source is set in one well and a receiver array in another well, we obtain one half of the image between two wells. Then we change the former shooting well into the receiving well and former receiving into shooting well, to obtain the corresponding opposing half image. Imaging both halves constructs the full image. In comparison with a conventional layout, the new layout is oriented to acquisition of reflection signal instead of first breaks for tomography, which reduces the costs of field operation, shortens the cycles of data processing and interpretation.