The fractured-vuggy carbonate reservoirs with low porosity and low permeability basically have no oil and gas storage capacity. Fractures and caves are the main storage and permeability spaces

but fractures and caves have complex developed space and poor connectivity. Due to the limited sizes of fractures and caves during drilling in single well

and the failure of conventional water injection and acid fracturing reforms to achieve efficient expansion in remote well areas

single well production has high initial production

r

apid decline

and low production. Therefore

a field test of the high-pressure water injection volume expansion process was carried out

that is

using high-pressure water injection as an energy carrier to break through the barrier of an isolated fractured-vuggy system and achieve effective expansion. This process was tested in the well-S1 of Tahe Oilfield

and the effect was significant. The well was subjected to conventional water injection and oil replacement for 3 rounds in the early stage

and the effect gradually became worse. The production is characterized by constant volume. The seismic data show large-scale of the fractured-vuggy system around the well. Two rounds of high-pressure water expansion test are carried out

with the cumulative water injection of 2.98×10

4

m

3

and maximum injection pressure of 23 MPa. The water injection curves show that the high-pressure water injection make two fractured-vuggy systems around one well communicate with each other

improving the production status of this well. The cycle water content is reduced from 45 % to 4 %

and the production pressure drop is reduced from 29 MPa to 26 MPa. The production volume per unit pressure drop increased from 201 m

3

/MPa to 547 m

3

/MPa. So far

the cumulative oil increase has been 14 721 t. The tests show that the high-pressure water injection expansion technology can achieve the effective expansion of fractured-cavity carbonate wells with constant-volume

increase single-well production and reserves

and at the same time

create space for reducing the oil-water interface near the well

so as to extend the dry oil recovery period.