Abstract: In Beisantai area，Junggar Basin，73.11 percent of Cretaceous reservoir is low permeability reservoir. Clay minerals
in Cretaceous reservoir are mainly montmorillonite and disordered illite-montmorillonite. Kaolinite，chlorite and illite are at
lower levels overall，but local enrichment. Results of sensitivity experiments show that reservoir sensitivity of study area is
complex，a variety of sensitivity coexist and directly lead to low-yielding of oil reservoir. Water sensitivity is most strong.
Acid sensitivity experiments indicate that mud acid can’t improve reservoir quality and reduce reservoir water sensitivity effectively.
According to specific reservoir property of study area，composite plug removal liquid with prescription of 8%HCl，
2%CH3COOH，2%NH4F，1.5%clay stabilizer A，2%ferric iron stabilizer TLJ is confected. Plug removal experiments of water
sensitivity samples and permeability improvement experiments of natural core samples are conducted under conditions with
stimulated actual formation temperature and pressure. Results show that the composite plug removal liquid is valid in plug
removal and permeability improvement on reservoir with high montmorillonite and illite-montmorillonite relative content but
low chlorite relative content.

Key words: Beisantai area, Cretaceous, low permeability reservoir, reservoir sensitivity, composite plug removal liquid, improvement experiment