Combination of Fluid Inclusion Data and Basin Modeling for the Reconstruction P,T,X,T Conditions in Cretaceous Oil Carbonate Reservoir from Gulf of Mexico

Bourdet, J.^1*, Pironon, J.¹, Levresse, G.², and Tritlla, J.^2
1UMR 7566/CNRS G2R-CREGU, Université Henri Poincaré, B.P. 23, 54501 Vandoeuvre-lès-Nancy, France
*[email protected]
²Prog. Geofluidos, CGEO-UNAM, Querétaro 76230 Mexico

Individual analyses of aqueous and hydrocarbon inclusions trapped in diagenesis mineralization, combined with petrographic information allow paleopressure and paleotemperature reconstruction at the time of trapping of fluid inclusions. However, in carbonate reservoir, fragility of carbonate crystals induces re-equilibration of most fluid inclusions which can record therefore post-trapping events.

Microthermometry and Confocal Laser Scanning Microscopy (CLSM) methods applied to petroleum inclusions allow homogenization temperature and gas percentage measurements respectily. Inclusions having the lowest Th in a same inclusion population are presumed to be preserved; the others are re-equilibrated. Moreover, this approach has been calibrated using PIT Software (Petroleum Inclusion Thermodynamics) by calculation of gas pecentage at 20°C and Th of virtual petroleum inclusions with known composition from condensate to black oil. This calibration is very useful to oil type estimate of natural petroleum inclusions, and visualization of multiple populations. In this case, we are able to reconstruct initial trapping P-T condition and post trapping P-T re-equilibration.

Thermobarometric reconstruction modelling of the well has been acquired by PetroMod® 1D in order to constrain timing of oil invasion in reservoir and also post-trapping events (burial, uplift, temperature increase).

This study presents an example of fluid inclusions analysis in carbonate reservoir well core of south part of Gulf of Mexico, from Cretaceous field of Chiapas-Tabasco area, central onshore part of South-East Basin. Petrographic study shows a finely crystalline planar-e non mimic replacement dolostone having two hydraulic fracturing stages filled by medium crystalline non-planar dolomite cement for the first and by a coarsely crystalline planar-e dolomite lining cement followed by blocky sparite cement for the second. Geological fluids are trapped in aqueous and hydrocarbon fluid inclusions in the last fracture filling cement. Microthermometry, Raman and infrared microspectroscopy have been used to characterize fluid compositions. Microthermometry and CLSM have been used to differentiate populations and preserved or re-equilibrated inclusions. Pressure and temperature of initial trapping have been reconstructed using PIT software. Burial model have been calculated from sedimentary log and permits to predict pressure and temperature evolution with time for the reservoir. It is concluded that reservoir was filled by two different black oils during post Miocene period. Maximum pressure trapping conditions record in fluid inclusions precisely correspond to fracturing pressure of the rock calculated using PetroMod® model. Re-equilibrated conditions of fluid inclusions are in good agreement with PetroMod® hydrostatic pressure in reservoir.

 

AAPG Search and Discover Article #90066©2007 AAPG Hedberg Conference, The Hague, The Netherlands

 

AAPG Search and Discover Article #90066©2007 AAPG Hedberg Conference, The Hague, The Netherlands