sed: command garbled

Im getting this error message when trying to substitute filepaths in a sed search and replace string

#!/usr/bin/ksh

ORACLE_SID=PH3
ORACLE_ADMIN=/data01/app/oracle/admin/$ORACLE_SID
DATAFILE_DIR=/asterisk/oradata/$ORACLE_SID

sed -e s/DBNAME/$ORACLE_SID/g < initPH2.ora | sed -e s/ORACLE_ADMIN/"${ORACLE_ADMIN}"/g | sed -e s/DATAFILE_DIR/"${DATAFILE_DIR}"/g > init$ORACLE_SID.ora

sed: command garbled: s/ORACLE_ADMIN//data01/app/oracle/admin/PH3/g
sed: command garbled: s/DATAFILE_DIR//asterisk/oradata/PH3/g

anyone got any ideas how I can stop the path of $DATAFILE_DIR or $ORACLE_ADMIN from escaping?

We do have a search function. I searched for "sed" and "garbled" and found this thread as well as a few others.