The invention discloses a suspended small cased well eccentric integrated double-
pipe separated injection
pipe column and a separated layer water injection method thereof, and aims to improve the later testing and adjusting success rate of small-
diameter separated injection construction and prolong the separated injection validity period. The separate injection
pipe column comprises an outer layer pipe and an inner layer pipe. The outer layer pipe comprises a conventional oil pipe, a double-flow-channel eccentric water
distributor, an outer connecting sleeve, an adapter connector, a small-
diameter oil pipe, a small-
diameter packer, a double-acting injection valve, a small-diameter
check valve, a screen pipe and a screwed plug which are sequentially connected from top to bottom. The inner-layer pipe comprises a first oil pipe connected to the lower inner end of the double-flow-channel eccentric water
distributor and a rear-throwing
ball type check valve. The layered water injection method comprises the steps of
tripping in a tubular column, pressing and setting, measuring a water
absorption index, putting a valve ball to control a water injection channel, and flushing a well. The method can achieve accurate layered water injection, improve the water injection efficiency and prolong the validity period of layered water injection, and is suitable for layered water injection operation of small cased wells.