The Xu-6 reservoir of Xujiahe formation in Guang’an area are fluvial sendiments,and the reservoir with best physical property are developed on the main branch river channel of the deltaplain.The reservoir rocks are mainly arcose and lithic sandstone,which are of low porosity and low permeability characteristics.The reservoir spaces are mainly original residual intergranular pores,and the secondary intergranular or intragranular pores.The study shows that the affection on reservoir of sedimentation are mainly by the controlling of sand distribution,rock fabric and physical property and so on.The physical property obviously decreased by the reconstruction of intensely compaction,pressolution and cementation,but the dissolution of feldspar in buried period improved the spaces.

Based on the outcrop features and conventional petrophysical properties,the reservoir characteristics of T1j2 of Zhaigouwan structure in eastern Sichuan are studied.The result shows that the reservoir rocks are mainly composed of crystal grain dolomite and particle dolomite.The reservoir spaces are mainly intercrystal pores and dissolved pores. The reservoir properties are poor.The reservoir types are fracture-pore and pore-fracture.Reservoirs mainly developed in T1j22 along longititudinal direction,less in T1j21 and partly in T1j23.Reservoirs of T1j22 developed well in Zhaigou 2 well and Zhaigou 4 well,while reservoirs of T1 j21 developed well in Zhaigou 4 well.Sedimentation not only controls the development and distribution of reservoir,but also affects the basic pattern of reservoir and the type and intensity of diagenesis.It is the dominated factor controlling the reservoir development.Diagenesis determines the reservoir space and reservoir performance,and directly influences the forming and evolution of pore space.Tectonism provides conditions for the above activities.

For Xujiahe Formation in Guangan area,its reservoirs mainly include Xujiahe 6 and Xujiahe 4 members.Characteristics of rock pore structure are the key factor affecting the reservoir capability of reservoir fluid(including oil,gas andwater),the hydrocarbon production and the permeable capability of reservoir rock.As a result,to make sure the characteristics isvery essential to increase both productivity and recovery efficiency.A conventional physical-property analysis forcore-sampling interval shows that the reservoirs in this studiedarea,which is characterized by very strong heterogeneity,belong to extra low-porosity and extra low-permeability to low-porosity and low-permeability ones.And there are in part some mediumporosity and low permeability reservoirs.Parameter variation ofpore structure was analyzed by mercury-injection experiment and the development of reservoir and the distribution and variation of pore and throat were also studied.In addition,the porosity,permeability and some pore structure parameters were calculated by a univariate regression method.After that,the relation diagram between pore structure index and reservoir productivity index wasdrawn up in terms of porosity and permeability.The result indicates that there is a high negative correlation between thesetwo indexes.