it could burst. there is more than oil coming out from under the mantle. there are rocks plus sand that act as abrasives and the pressures of oil leak is tremendous.
The pressure of the reservoir (and thus of the oil leak) is known and was measured in-situ as 11,000 psi. Well within the design specs of the BOP and the rest of the well. The "100,000 psi" number quoted so frequently exists only in the imagination of some fear-mongers.
This measurement was made and recorded before the blowout, when the well was stabilized with "mud" in place. Of course, 11,000 psi is still plenty enough pressure to cause problems if the cementing operations were defective and unable to withstand that 11,000 psi stress once the "mud" was removed.