Abstract:

Plentiful natural gas resource has been discovered in Carboniferous volcanic rocks in Ludong-Wucaiwan area in
Junggar Basin in recent years. Kelameili and Wucaiwan gas fields were found in this area， and Carboniferous has been one of
the major targets in oil and gas exploration in northern Xinjiang. As a special type of reservoirs，volcanic reservoirs have attracted
wide attention. The natural gas in Ludong-Wucaiwan area was mainly preserved in the weathering crust of volcanic rocks at the
top of Carboniferous，and was mainly coal-derived gas from Carboniferous humic-type source rocks. Ludong-Wucaiwan area
could be divided into several secondary tectonic units，and the gas reservoirs were mainly located at the middle-west parts of
Di’nan Uprise and Wucaiwan Sag. The accumulation properties of oil and gas in volcanic reservoirs are different from those in
conventional ones. Besides the well reservoir quality，the matching of several favorable factors such as hydrocarbon generation,
migration, and preservation were also necessary. Based on the analysis of typical gas reservoirs in Ludong-Wucaiwan area, thispaper is focused on the major controlling factors on the enrichment of natural gas in Carboniferous volcanic rocks. The results
indicate that it is favorable to form reservoirs if the volcanic rocks were adjacent to source rocks and hydrocarbon-generation
sags；The reformation by and tectonism was a key factor to improve the reservoir quality of Carboniferous volcanic rocks in
Ludong-Wucaiwan area and to develope effective reservoir space ；The faults and the unconformity were the favorable pathways
for vertical and lateral migration for oil and gas；The Carboniferous traps and reservoirs in Ludong-Wucaiwan area have been
affected by different degrees in different stages since the Hercynian，in which the favorable source-reservoir-seal assemblages
for the volcanic reservoirs were finalized in the Hercynian; while the Middle Yanshanian period was the key stage for natural gas
accumulation.

Key words: Ludong-Wucaiwan；volcanic rocks；natural gas；controlling factors；tectonic evolution