Characteristics and hydrocarbon exploration in the Himalayan faulted basins in Yunnan: Examples from the Baoshan and Qujing Basins in Yunnan

There are a lot of fault basins and pull-apart basins created by the Himalayan orogeny in Yunnan, among which the Baoshan and Qujing Basins have similar features and witnessed, without exception, four evolutionary stages of extension, rift faulting, downwarping and uplifting/collapse. Influenced by the second episode of the Himalayan orogeny, the Miocene deposits are absent in the Qujing Basin. The source rocks consist primarily of bathyal-abyssal dark mudstones and marshland plain coal measures generated during the rift faulting and downwarping stages of the basin. The organic carbon contents only range between 1% and 2%, and the organic carbon maturity is relatively low. The reservoir rocks are mainly made up of steep slope alluvial-pluvial sandstones and conglomerates, delta front sandstones and delta plain subaqueous distributary channel sandstones, with higher porosity and lower permeability. Except structural gas reservoirs, particular attention should be drawn to the favourable lithologic gas reservoirs in the alluvial-pluvial facies near the steep slope zones and delta front facies in the ramp zones.