Research and application of hydrophobic reducing pressure and increasing injection liquid system of injection well

In order to solve the problems of insufficient water of injection wells with long-term high pressure and short validity period in Changqing Oilfield Y19 block, the lab analysis tests of rock mineral composition, reservoir sensitivity, compatibility of formation fluid and water injection were carried out. The main factors causing insufficient water of injection wells with high pressure were found, these were wettability reversal, fouling blocking and sensitivity of reservoir. In this regard, a set of hydrophobic antihypertensive liquid system consisting of low harm acid liquid, sulfate scale release agent, hydrophobic nanomaterial slug was developed in laboratory. The liquid system could effectively remove chemical fouling blocking, improve the wettability of rock surface and reduce water flooding capillary resistance.Thus the main contradiction caused by insufficient water injection under high pressure of injection wells was fundamentally solved. Two wells completed field test both reach the injection distribution requirements, the injection pressure drop was over 2 MPa, the total increasing injection amount was 8 077 m³, and the period of validity extended more than 4 months compared with conventional measure. The application has achieved a good effect, and provided effective technical means for reducing pressure and increasing injection operation of low permeability oilfield.