I asked my D-I-L who told me that the sovereign rule for orchids is to have a free draining mix.. Although she does use orchid potting mix, she has also used chipped bark mixed with a little extra peat and perlite. I looked at the mix she left in my greenhouse. It looks very similar to basic bark chips mixed with coarse bulb compost. I do think that you can make use of what you have. Chop it a little bit finer and mix in a handful of moss from the lawn (I kid you not), a handful of perlite or horticultural grit and repot away. It seems that they also need a low fertility mix with the bark essentially acting as an anchor for the roots still in the soil (which determines the size of the bark chips). Obviously, those fat white arial roots are perfectly OK with a spritzing of distilled water (or at least, tapwater which has been left to stand for 24 hours so chlorine gases can sublime off). She did say to use those clear pots with drainage holes in the sides as light is essential for the roots and overwatering is the main cause of death. basically, you need to be able to pour water on the mix and watch it drain out almost as fast as you can water.
I spoke to someone from the HPS who also suggested those clay granules (hydroleca) are good in orchid growing mediums. Are you talking about phals here?...or cymnbidiums, dendrobiums etc.