8 | Halliburton Landmark
Figure 4 > Porosity-permeability plots indicating the primary ( A ) and secondary ( B ) controls on reservoir quality within Cenomanian – Turonian carbonate reservoirs . Data are derived from the Neftex ® Rock Properties Database .
of these siliciclastic units can be correlated with confidence over 100s of kilometers ( Droste and Steenwinkel , 2004 ; Craigie , 2015 ).
The western part of the correlation is along a depositional dip through the Shilaif intrashelf basin margin . Progradation and downstepping of Mishrif Formation rudist-rich carbonate shoals is observed , along with the thinning of Cenomanian sequences into the intrashelf basin . The carbonate shoals form prolific reservoir intervals and were deposited during progradation of the shelf margin in the HST . In the Turonian , a thick siliciclastic LST ( Tuwayil Formation ) infilled much of the remaining accommodation space within this intrashelf basin ( Al Zaabi et al ., 2010 ; Vahrenkamp et al ., 2015 ).
The petroleum system elements that have been annotated along this correlation can be directly related to both the paleogeography and morphology of the depositional system . Importantly , this gives confidence in the prediction of these petroleum system elements away from data control in more frontier areas . This is where Neftex Gross Depositional Environment ( GDE ) maps are invaluable , as they predict the distribution of petroleum system elements at the regional scale , and within the high-resolution temporal framework of the Neftex Sequence Stratigraphic Model .
CONTROLS ON RESERVOIR QUALITY
Reference transects and regional correlations have revealed that rudist-rich carbonate reservoirs are prevalent within the HST succession . Porosity-permeability data from the Neftex Rock Properties Database demonstrate the key controls on reservoir quality in these carbonate reservoirs ( Figure 4 ).
The data in Figure 4A were taken from the Mishrif Formation in platform margin locations in Iraq and the United Arab Emirates . The plot demonstrates a primary control on reservoir quality related to depositional facies . There is a clear increase in porosity and permeability from basinal and lagoonal facies ( poor-quality reservoir ) to grainy shoal and rudist biostrome facies ( high‐quality reservoir ) ( Aqrawi et al ., 1998 ; Perrotta et al ., 2017 ).
Figure 4B shows data from the Sarvak Formation in platform interior areas of Iran , away from intrashelf basin margins . The plot shows a trend influenced by depositional facies ( black arrow ). However , there is significant deviation from this trend , where high permeability samples are associated with low porosity . This secondary trend ( red line ) appears independent of depositional facies , with high permeability occurring in lagoonal environments that are not