The reservoir rocks of Lower Cretaceous Fuyu and Yangdachenzi unites wrer deposited in channels on the deltaic flood plain in Sanzhao area. The reservoir rocks mainly consist of fine lithic arkose and feldspathic litharenite with abundant matrix.Porosity ranges from 1% to 21.3%

with a mean of 10.9%.Permeability ranges from 0.01×10

-3

to 289×10

-3

μm

2

with a mean of 1.53×10

-3

μm

2

.Main diagenesis includes compaction

cementation

dissolution

replacement and recrystallization.According to the texture;cathodoluminescence characteristics

carbon and oxygen isotopic composition

the contents of the main and trace elements

calcite cement formed in reducing condition during early diagenesis. Precipitation of calcite cement caused the decrease of porosity in sediments.Porosity formed by feldspar and intermediate/basic volcanic rock fragment dissolution makes up about one third of the whole porosity.Most smectite and kaolinite already changed into illite and chlorite

or mixed layered illite/smectite(I/S)and chlorite/smectite(C/S).Most changes of reservoir rocks occurred during early diagenesis.