The injection of hydrogen is carried out under a pressure sufficient to cause {TAIL ~ the injected hydrogen} to become absorbed within {HEAD ~ the matrix} of the carbonaceous formation 
The injection of hydrogen is carried out under a pressure sufficient to cause { TAIL ~ the injected hydrogen } to become absorbed within { HEAD ~ the matrix } of the carbonaceous formation
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH