Deep-buried clastic rock reservoirs in Hexiwu structureal belt of Langgu Depression mainly consist of feldspathic sandstone with low compositional maturity and middle textural maturity. The deep elastic rocks are in late diage-. nesis stage( A

Ⅰ

-A

Ⅱ

)

the physical property of the reservoirs become much more worse. A secondary pore belt developed in the section. From 3 450 m to 3 550 m

intragranular and intergranular solution pores developed well

thus forming available reservoirs

fluid solution caused by decarboxylation of organic acid was the major formation mechanism of secondary pores at the deep section. Pore structure is mainly characterized by small pore-low permeability-fine throat. The content of carbonate

sedimentary fades and diagenesis are the principal factors offecting the physical property of the reservoirs. The porosity of reservoirs in Langfang

Hancun and Beiwang is the highest in Hexiwu structural belt. These places are favourable for the development of the reservoirs.