The reservoir characteristics

controlling factors and sensitivities of the Middle Jurassic Toutunhe Formation in Fudong slope

Junggar Basin

were studied based on core observation

casting thin section identification

assisted with some analytical and experimental data on cores

such as SEM data

physical property depiction

x-ray diffraction results

pore structure and sensitivity test.Results show that:(1) the most favorable micro-facies for reservoir development is underwater distributary channel at delta front and its lithology is mainly composed of feldspathic litharenite that is low in compositional maturity and medium high in textural maturity.The reservoir space is mainly primary residual intergranular pores

partly intergranular and intragranular dissolved pores;(2) displacement pressure and mean saturation pressure are relatively low

but the pore throats are well-sorted

narrow as a whole

and are dominated by capillary throats;(3) reservoir development is controlled by both sedimentary microfacies and diagenesis;the early diagenetic chlorite rim cementation is beneficial to the preservation of some primary pores and throats

but compaction and pressure-solution causes the shrinkage of the primary pore space

the lowering of reservoir permeability

and the tightening of reservoir rocks.In addition

the sandstone reservoirs of the Toutunhe Formation generally have various sensitivities

which is one of the main causes of reservoir damage.Among them

the medium strong water sensitivity is the strongest in reservoir damage

followed by the medium weak acid sensitivity and salt sensitivity

while weak velocity sensitivity is hardly harmful.