The porosity and permeability of Mahu sandy conglomerate tight reservoir in Xinjiang are extremely low. After fracturing and putting into production

the stable production effect of early development is good

and the decline is large in the later stage. In order to supply the formation energy and improve the crude oil recovery

the tests of CO

2

huff and puff for three horizontal wells have been carried out in Ma131 well area. The test results show that the mechanism of CO

2

huff and puff to improve crude oil recovery is mainly reflected in increasing reservoir energy

expanding crude oil volume

reducing crude oil viscosity

extracting light compo

nents

dissolving reservoir minerals and increasing fluid flow capacity. Reasonable injection parameters are more helpful to enhanced oil recovery. During the development of CO

2

huff and puff

the higher bottomhole injection pressure and the longer soaking time

as well as greater sweep diffusion

result in earlier continuous oil production and more obvious enhanced oil recovery effect. The oil increment of three horizontal wells

Well-X721

Well-X92 and Well-M1114

is 2 161 t

1 768 t and 1 452 t

respectively. CO

2

huff and puff has good adaptability and popularization and application prospect in sandy conglomerate tight reservoir.