A Method for Improving Underbalanced Pressure Design in Injection Wells Using Negative Pressure Blocking

In order to improve the effect of negative pressure blocking in injection wells,the design method of negative pressure blocking in injection wells was studied.According to the seepage characteristics of injection wells,an additional pressure drop due to the skin factor was utilized to correct the minimum negative pressure.The maximum negative pressure was designed following principles of sand control.Afterwards,the optimized negative pressure was determined according to the negative pressure design method of ConocoPhillips.Finally,the negative pressure was checked on the basis of preventing casing damage and ensuring the stability of pay zone.The new method of the negative pressure value design was applied to Well Che2 and Well Che89.After the utilization of the negative values recommended by the new method,both water injection pressures of Well Che 2 and Well Che 89 were lowered obviously,and the water injection pressures did not increase substantially.The results showed that using the new negative pressure plugging method in vertical wells of medium or high permeability sand stone pay zones could clear the pollution of the near well bore area and ensure the stability of bores and pay zones.