Abstract
The Qaidam Basin has experienced multiple tectonic movements since the Carboniferous. Investigating the formation, adjustment, and alteration of oil and gas reservoirs is helpful to optimize exploration targets. Oil and gas charging, accumulation, and adjustment in the Carboniferous Keluke Formation in the eastern Qaidam Basin were comprehensively analyzed through integrating fluid inclusion petrographic observations, homogenization temperature and salinity determination, basin modeling, bitumen geochemical analysis, and balanced crosssection restoration. Fluid inclusions and basin modeling show an early single-stage and continuous hydrocarbon generation in the Keluke Formation. The C(2)k(2) source rocks became marginally mature, mature, and highly mature at 312 Ma, 298 Ma, and 248 Ma, resulting in oil generation at the marginally maturity stage, oil-gas coexistence at the mature stage, and gas generation at the high maturity stage. While the C(2)k(4) source rocks were marginally mature and mature at 273 Ma and 248 Ma, respectively. Bitumen geochemical analysis and balanced cross-sections indicate that a subsequent paleo-reservoir adjustment and structural alteration resulted from multiple uplifts and faulting activities after early hydrocarbon generation in the Ounan Sag. The adjustment could be confirmed using hydrocarbon inclusions with an abnormally low salinity and homogenization temperature and fluorescence. Secondary oil and gas reservoirs in the Ounan Sag and the deep-buried oil and gas reservoir in the structurally stable Delingha Sag are considered to be potential exploration targets.
NSTL
Elsevier