By adopting quantitative evaluation of pore throat parameters under different depositional and diagenetic conditions

and with reference to the test results of physical property

casting section

SEM

constant speed mercury injection

particle size and X diffraction

the pore throat types of Chang 8 reservoir of Heshui Region and Chang 6 reservoir of Xuecha Region in Ordos Basin were analyzed

contrasted and reasons for how they were formed were revealed.Results show that the pores are better developed in Chang 8 reservoir in Heshui Region

with a high quantity of intergranular

dissolved

intercrystalline and micro pores

as well as necking down throats with weak compaction

tube-shaped throats with dissolution and clay cementation; while pores are less developed in terms of both types and range in Chang 6 reservoir of Xuecha Region

with high quantity of lamellar and curved lamellar throats with compaction.For the two studied reservoirs

the differences in pore parameters are not as significant as those in throat parameters.Compared to Chang 6 reservoir

Chang 8 reservoir developed better and larger throats with apparent differences

bigger pore-throat ratio

and wider distribution of throats that are conducive to permeability.Under the condition of same permeability

the average throat radius

main flow throat radius and pore-throat ratio of Chang 8 reservoir are all bigger than those of Chang 6 reservoir.It can be concluded that the hydrodynamic conditions in sediments

particle size

detrital component

interstitials

diagenesis types and their respective influence degrees

are the main reasons for the differences in the development of pores

throat types and pore throat parameters.