In Iraq, the large number of wells and the long production history of Kirkuk, Bai Hassan, Jambur, Rumaila (S & North) and Zubair Fields allowed better control of reservoir performance. The results of repeated reservoir simulation studies enabled refined and higher estimate of the RFs. In contrast to that, the reservoirs in those fields that were discovered and either not put into production or had short production periods retained conservative estimate of the recovery factor.
Further reservoir modeling should be based on new 3D detailed seismic and other data acquisition that would decide more supported reserve estimates than the current official reserved figures.
In the case of the discovered fields that were not connected or put on limited pilot production:
- Some fields/ reservoirs were not fully delineated that means the estimate of OOIP and eventually the recoverable reserves (P1) is conservative
- The number of wells was small imposing a restriction on knowledge of reservoir geology and reservoir characteristics in addition to insufficient well and reservoir testing
- No or limited possibility of monitoring and reservoir modeling
In those fields, 3D detailed seismic drilling, well testing and may be selective Pilot Production for at least one to two years is a pre-requisite to reservoir studies. All is required to assess the reserves and assist achieving full development.
Independent analysis of the RFs of the 63 fields containing 84 reservoirs (Figure-1) showed that there is definitely appreciable margin of justifiable increase. The low RFs were upgraded to 35%-45% ( well achievable) assuming future enhancement techniques to be carried out after obtaining further specific data and performing reservoir studies of almost all the fields/ reservoirs of Iraq. The recoverable total reserve P1 from the study (146 BB, Annex-1) is very close to last official figure of 142BB MoO announced last year