--> ABSTRACT: Application of <SUP>87</SUP>Sr/<SUP>86</SUP>Sr, ^dgr<SUP>18</SUP>O and ^dgr<SUP>13</SUP>C Isotopes To Diagenesis, Correlation And Connectivity of a Fractured Chalk Reservoir, The Sidi El Kilani Field, Tunisia, by Euan W. Mearns, Mark Bramwell, and John J. McBride; #91019 (1996)

Datapages, Inc.Print this page

Application of 87Sr/86Sr, ^dgr18O and ^dgr13C Isotopes To Diagenesis, Correlation And Connectivity of a Fractured Chalk Reservoir, The Sidi El Kilani Field, Tunisia

Euan W. Mearns, Mark Bramwell, and John J. McBride

Oil is produced primarily from open fracture porosity in Upper Cretaceous chalk in the Sidi El Kilani oil field. Strontium Stratigraphy analyses of primary, unaltered matrix chalk has confirmed a Campanian to Maastrichtian age and has allowed dating of the reservoir with a resolution of ±1 Ma. This has facilitated reservoir correlation and has indicated where section is missing in certain wells due to faulting.

87Sr/86Sr, ^dgr18O and ^dgr13C analyses suggest an early generation of fracture fill calcite cement may have formed by redistribution of CaCO3 from underlying carbonate sequences at temperatures in the region 35-55°C. Calcite cemented fractures tend to be healed and are not productive.

Strontium Isotope Residual Salt Analyses (SrRSA) conducted on core, provide information on the formation water chemistry and reservoir connectivity at the time of oil filling. These data suggest that the NW-SE trending fault system that bisects the field is sealed across much of the fault plane. The main oil pool lies SW of the fault.

A later generation of dolomite and barite cements, associated with productive open fractures, have Sr-O-C composition consistent with precipitation from fluids circulating at the time of hydrocarbon charge at temperatures close to current reservoir conditions of 70-75°C. Predicting the distribution of dolomite cemented open fractures has thus helped guide the development strategy of the field.

AAPG Search and Discover Article #91019©1996 AAPG Convention and Exhibition 19-22 May 1996, San Diego, California