Pore pressure prediction and compartmentalization of the tertiary oil reservoirs from sonic log in the khabbaz oil field, Northern Iraq

الملخص EN

The Tertiary oil reservoirs in the Khabbaz Oil Field comprise the Jeribe, Anah, Azkand, and Ibrahim formations.

This study aims to manage unpredicted pressure changes that occur in wells drilled in the carbonate reservoirs, which are potentially dangerous and financially cost during petroleum exploration.

It has studied from pore pressure and reservoir compartmentalization points of view.

Eaton method has been used to predict the pore pressure from the sonic log data.

The basic assumption for this technique is the interrelation between observed transit time from log reading and normal transit time that locates on the normal compaction trend (NCT).

The bulk density is determined from sonic log and has a good match with the bulk density derived from the density log.

It shows that the sonic log can be used as a good alternative to obtain the bulk density and consequently to determine lithostatic pressure.

Pore pressure depends upon changes in the overburden gradient.

Based on predicted pore pressure, the studied reservoirs compartmented into four pressure zones.

The number of the zones is identified by using a graphical method of probability plot of the predicted pore pressure on the basis of cluster analysis.

All reservoirs are assumed to be overpressured zone.

According to predicted pore pressure, the Azkand Formation is the most potential reservoir because it has the highest-pressure value measured from the top of the Azkand Formation to the bottom of the Ibrahim Formation.

Direct relation between pressure, temperature and thickness of hydrocarbon zones (oil and gas) gives indications that most of the studied reservoirs are of good productivity at primary recovery stage.