Preliminary study on the effects of Permian volcanism on the Tahe Ordovician oil pools in Tarim basin

Crude oil densities change remarkably among the various oil pools of Tahe field. Multi-stage generation and recharge of light oil and gas from source rocks during pool formation have been assumed to account for this phenomenon. The hypothesis of multi-stage recharging and pool formation, however, is in conflict with the assumptions deducted from paleo-structure evolution and stratigraphic pressure of the pools. Variations in salinity of stratigraphic water indicate that heavy oil cannot possibly be connected to fresh water oxidization associated with the unconformities over the oil pools. Utilizing research on the distribution of Permian volcanic craters, conduits, and rocks interpreted from well and 3-D seismic data, the present study shows that the closer the pools are to the volcanic conduits, the denser the oil is. Volcanic activity does not occur at the eastern Tahe pool, which shows normal oil and condensate gas. The findings illustrate the impact of Permian volcanic activity on Ordovician oil pools.