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title of the reference :
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Dolomitized Abiod Formation
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Publication Date:
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1998
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Author :
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Beck B.J., Amiri Garboussi K
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Catalogue type :
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Livre
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Catalogue reference :
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Dolomitized Abiod Formation A new hydrocarbon play fairway in Tunisia Recent drilling in the North Kairouan area indicates that the Abiod Formation is preferentially dolomitized where it is either proximal to, or truncated by, a regional tertiary unconformity. Dolomitized Abiod Formation can form subsurface hydrocarbon reservoirs, it fractured in the presence of suitable source-rock and sealing formations. Seismic time interval maps of top Abiod Formation to the regional Tertiary unconformity highlight the dolomite play fairway can be used to identify and rank existing prospects. Petrography, geochimistry, micropaleontology and wireline log analysis of the Abiod Formation in Chorbane East well recently drilled by KUFPEC/ETAP, indicate : *The Abiod Formation is 375 m thick and represents the Campanien age. It is overlain by a 30 m undifferentiated interval: yielding early Campanien and early Maastrichien microfauna, that cannot be correlated with formations is near by wells on the existing lithological, biostratigraphic and wirreline log data. *An unconformity separetes the undifferentiated interval from the overlying Lower Miocene strata. The middle-Upper Maastrichien, Paleocene, Eocene and Oligocene are absent. *The Abiod Formation is pervasively dolomitized and fractured. The fractures are pertially cemented by baroque dolomite. Matrix core porosity is 10-14% with permiability less than 1m D. Fluid production is mainly from intervals with open fractures and vugs. *The Matrix dolomite 87Sr/86Sr ratio is< 0,7085 and may represent a mixture of 87Sr/86Sr ratio of pre-existing carbonate (Abiod Formation=0,7077) and dolomitizing fluid (>0,7086). *The Sr87/86Sr ratios of produced water and Abiod Formation matrix are consistently higher than those recorded in the near by Sidi El Kilani Field. This is interpreted to indicate that the Abiod Formation in CNE-1 was closer to the source of dolomitising fluids than in the Sidi El Kilani Field. *Fracture-filing cement precipitated after matrix dolomitization and at temperatures 8°-9°C higher as indicated by Sr-O-C results. This cement was also formed from externally derived dolomitizing fluids, with 87Sr/86Sr ratios, though some contamination cannot be ruled out. Regional seismic time interval maps of top Abiod Formation to Oligocene unconformity, calibrated with well data, can be used to predict the dolomite play faiway occurence in the area.
puits reconnaissance ; Campanien ; sismique réflexion ; forage ; hydrocarbure ; dolomitisation ; lithostratigraphie ; profil sismique ; diagraphie ; Formation Abiod ; Tunisie ; Tunisie Centrale Kairouan ; Chorbane Beck B.J. Amiri Garboussi K Roches sédimentaires
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Indexation decimale :
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Roches sédimentaires
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Keywords :
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puits reconnaissance ; Campanien ; sismique réflexion ; forage ; hydrocarbure ; dolomitisation ; lithostratigraphie ; profil sismique ; diagraphie ; Formation Abiod ; Tunisie ; Tunisie Centrale Kairouan ; Chorbane
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Summary :
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Recent drilling in the North Kairouan area indicates that the Abiod Formation is preferentially dolomitized where it is either proximal to, or truncated by, a regional tertiary unconformity. Dolomitized Abiod Formation can form subsurface hydrocarbon reservoirs, it fractured in the presence of suitable source-rock and sealing formations. Seismic time interval maps of top Abiod Formation to the regional Tertiary unconformity highlight the dolomite play fairway can be used to identify and rank existing prospects. Petrography, geochimistry, micropaleontology and wireline log analysis of the Abiod Formation in Chorbane East well recently drilled by KUFPEC/ETAP, indicate : *The Abiod Formation is 375 m thick and represents the Campanien age. It is overlain by a 30 m undifferentiated interval: yielding early Campanien and early Maastrichien microfauna, that cannot be correlated with formations is near by wells on the existing lithological, biostratigraphic and wirreline log data. *An unconformity separetes the undifferentiated interval from the overlying Lower Miocene strata. The middle-Upper Maastrichien, Paleocene, Eocene and Oligocene are absent. *The Abiod Formation is pervasively dolomitized and fractured. The fractures are pertially cemented by baroque dolomite. Matrix core porosity is 10-14% with permiability less than 1m D. Fluid production is mainly from intervals with open fractures and vugs. *The Matrix dolomite 87Sr/86Sr ratio is< 0,7085 and may represent a mixture of 87Sr/86Sr ratio of pre-existing carbonate (Abiod Formation=0,7077) and dolomitizing fluid (>0,7086). *The Sr87/86Sr ratios of produced water and Abiod Formation matrix are consistently higher than those recorded in the near by Sidi El Kilani Field. This is interpreted to indicate that the Abiod Formation in CNE-1 was closer to the source of dolomitising fluids than in the Sidi El Kilani Field. *Fracture-filing cement precipitated after matrix dolomitization and at temperatures 8°-9°C higher as indicated by Sr-O-C results. This cement was also formed from externally derived dolomitizing fluids, with 87Sr/86Sr ratios, though some contamination cannot be ruled out. Regional seismic time interval maps of top Abiod Formation to Oligocene unconformity, calibrated with well data, can be used to predict the dolomite play faiway occurence in the area.
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