Carbon Dioxide Generation from Coals in Taranaki Basin, New Zealand: Implications for Petroleum Migration in Southeast Asian Tertiary Basins

Authors:
  • SKS. D. Killops
    S. D. Killops
  • RAR. G. Allis
    R. G. Allis
  • RFR. H. Funnell
    R. H. Funnell
Publisher website
Google Scholar
Abstract
Elevated CO2 levels in gas accumulations within the onshore area of the Taranaki Basin can be quantitatively accounted for by decarboxylation of vitrinite-rich Tertiary coals over the lignite to early high-volatile bituminous coal-rank range. The highest levels are found within sandstone reservoirs vertically adjacent to Eocene coal seams that have realized approximately 50% of their CO2 generative potential. The gas exists as a supercritical fluid under reservoir conditions and appears to be generated in significant amounts, comparable to liquid hydrocarbons. CO2 may aid oil expulsion from coals directly when intense CO2 generation coincides with major oil generation, or indirectly by creating pressure-induced microfractures during the relatively rapid generation of large amounts of CO2 prior to the main phase of oil generation. For these effects to be realized, the rate of CO2 production relative to removal is considered critical, and favorable conditions are probably restricted to basins that have experienced relatively rapid heating. In this respect, the Taranaki Basin provides a model for CO2 evolution in many southeast Asian Tertiary basins.

This publication has 38 references indexed in Scilit: