Paleo-Thermo-Barometers, Paleoburial and Unroofing History in Fold and Thrust Belts: Applications to Hydrocarbon and Reservoir Prediction
1Institut Français du Pétrole, 1-4 Ave. de Bois-Préau, F92852 Rueil-Malmaison; France
Basin modelling tools are now more efficient to reconstruct palinspastic structural cross sections and compute the history of temperature, pore fluid pressure and fluid flow circulations in complex structural settings.
In many cases and especially in areas where limited erosion occurred, the use of well logs, BHT and paleo-thermometers such as Ro and Tmax is usually sufficient to calibrate the heat flow and geothermal gradients across a section. However, in the foothills domains erosion is becoming a dominant process, making challenging the reconstruction of reservoir rocks paleoburial and the corresponding calibration of their past thermal evolution. Many times it is usually not possible to derive a single solution for paleo-burial and paleo-thermal gradients estimates in the foothills, if based solely on maturity ranks of the organic matter.
Alternate methods are then required to narrow down the error bars in paleo-burial estimates, and to secure more realistic predictions of HC generation: AFT can provide access to absolute ages for the crossing of the 120°C isotherm and timing of the unroofing, whereas hydrocarbon-bearing fluid inclusions, when developing contemporaneously with aqueous inclusions, can provide a direct access to the pore fluid pressure and temperature of cemented fractures or reservoir at the time of cementation and HC trapping. Further attempts are also currently made to use calcite twins for constraining reservoir burial and paleo-stress conditions during the main deformational episodes.
The methodology integrating these complementary constraints will be illustrated using reference case studies from the Mediterranean, Latine America, Canada and the Middle-East.
AAPG Search and Discovery Article #90091©2009 AAPG Hedberg Research Conference, May 3-7, 2009 - Napa, California, U.S.A.