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Abstract: Preliminary Basin Modeling Results from the Fergana Basin, Kyrgyzstan

JOHANSEN, HELGE and LINDA M. BONNELL, Geologica a.s. Torstein Hoie, Smedvig Technologies.

The purpose of this study was to improve the understanding of hydrocarbon maturation in the Fergana Basin, Kyrgyzstan by reconstructing the geological history (sedimentation, erosion, and structural reconstruction), and modeling the thermal history; and the timing, magnitude, and phase of hydrocarbon generation using the basin modeling system BMTTM. Two cross sections from the North Eastern Fergana Basin were modeled. Temperature data of uncertain quality were available from wells in the area, but vitrinite reflectance data was only measured in other parts of the basin.

The lack of good calibration data led to an increased uncertainty in modeling results and in order to better constrain the timing and phase of generated hydrocarbons, we assessed the impact that uncertainties in present day thermal gradient, heat flow history and kerogen type had on model predictions. Three different paleo heat flow model were used; Higher heat flow in the past, constant heat flow in the past, and lower heat flow in the past.

Potential source rocks of Tertiary, Jurassic, and Paleozoic age have been identified in the basin Model results indicate that Tertiary source rocks with type II kerogen buried less than 4500m are immature regardless of the flow model. Tertiary source rocks deeper than 4500m are modeled to be in the early stages of maturation. Jurassic and Paleozoic source rocks have reached maturity but the extent and timing of the hydrocarbon generation are very sensitive to the heat flow model. Due to differences in kinetics, source rocks with Type II kerogen have reached a higher maturity level than Type III kerogen for all thermal models.

AAPG Search and Discovery Article #90937©1998 AAPG Annual Convention and Exhibition, Salt Lake City, Utah