The Mesozoic volcanic rocks in Fenghuadian

Huanghua depression

mainly consist of rhyolites

trachydacites

trachytes and minor trachyandesites and dacites. Two lithofacies

volcanic explosion(including explosion and effusion subfacies) and volcaniclastic lithofacies can be distinguished. Reservoir in different lithofacies are characterized with different reservoirs physical properties

the volcanic explosion subfacies are the most favorable reservoirs. Different locations of volcanic rock in terms of palaeo-geomorphology have a great impact on the reservoir quality. Upper portion of the lava of the volcanic effusion subfacies in the highland of palaeo-geomorphology and in the hinge area are believed to be ideal oil and gas reservoirs. It is indicated by organic geo-chemical researches that source rock samples gathered from the volcanic rocks are quite similar to TIC chromatograph of mudstone extracts and saturated hydrocarbon chromatograph from Member Ⅱ

Ⅲ of Kongdian Formation

sterane and hopane of crude oil also have similarities with mudstone from Member Ⅱ of Kongdian Formation

therefore

the Eocene Member Ⅱ(E

K

2

)of Kongdian Formation overlain the Suite and in Cangdong depression is the principal source rocks for generation of hydrocarbons reserved in Fenghuadian suite.The faults in the suite may have acted as conduits for hydrocarbon migration.