this is expected. Oracle Linux is not supported and has no reconfiguration specific code. At about 97% of conversion task begins the reconfiguration of the destination VM which is specific for each distro.
You will need to do that manually. Boot the VM with a live CD (preferable the installation one) and from there install GRUB and build the initrd image. Check also fstab file.
I know this is old, and I do not have a solution, but I have successfully P2V'd an OEL6.5 from OVM/XEN vm to VMware using converter 6. Yet another OEL 6.5 fails during tar. The product is just not that great. Why in the world would you create this "HELPER" vm with 512MB ram anyway? This seems to be 50% of the issues. And the answer on how to up the RAM is incomplete.