so the well is holding back ONLY 6700 psi?
It makes a difference if that's "gage" pressure or absolute. Gage pressure would be referenced to the well head which is some 5000 feet below sea level, thus ignoring the 2236 psi of the ambient environment. If it is an "absolute" reading it includes the 2236 ambient and therefore the differential from the well head to the bottom of the bore hole is only about 2/3 of the quoted 6700 psi.
Usually, in open air, the difference between gage and absolute readings can be safely ignored as the 14.7 psi of (standard) atmospheric pressure is decimal dust and won't affect the resultant calculations all that much. However, when the environment is nearly a mile deep in sea water it makes a huge difference.
I don't think anyone has asked the question as to just what is the basis of reference for the pressure reading.
Regards,
GtG
I have this picture of Obama dressed like the Dutch Boy with his finger in the well...