Method for recharging sewage produced in natural energy exploitation stage of oil field to underground

The invention provides a method for recharging sewage produced in the natural energy exploitation stage of an oil field to the underground. The method comprises the steps that 1, the annual sewage output of the oil field in the natural energy exploitation stage is measured and calculated; step 2, screening an underground sewage recharge layer; step 3, measuring and calculating the amount of sewage which can be accommodated by the sewage recharge layer; 4, injection testing is carried out, and water injection evaluation is carried out on the recharge layer; 5, measuring and calculating the minimum water absorption capacity of the single well of the recharge well; 6, the minimum number of recharge wells needed for completing the sewage recharge task is measured and calculated; 7, measuring and calculating the static water absorption capacity of the single well of the recharge well; 8, the water injection life period of a single well is measured and calculated; 9, the accumulated water injection rate in the wate