Is it possible to export an image sequence (in this case a sequence of .exrs) from cycles?
For example, I have multiple sets of .exrs for different passes I want to combine into one set of .exr image sequences.
To save all the passes for each frame into a multilayer OpenEXR:
Add an Input>Image Sequence node and use that to import the OpenEXR sequence
Add an Output>File Output Node and set it to Use OpenEXR multilayer and plug the outputs of the Image sequence to it.
You still need a valid output for the render. So create a dummy file, a jpeg file will do. You can erase those later.
Then just set your frame range and render as animation (ctrl F12)
(and remember to erase the jpeg dummy files)