The deasphalting residue is then added to a second portion of {HEAD ~ heavy oil}, such as {TAIL ~ a second portion} of the same type of heavy oil that was used as feedstock in the solvent deasphalting 
The deasphalting residue is then added to a second portion of { HEAD ~ heavy oil } , such as { TAIL ~ a second portion } of the same type of heavy oil that was used as feedstock in the solvent deasphalting
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH