陕北特低渗储层注水井序列化复合解堵体系OA

To address the challenge of a sudden surge in water injection pressure caused by composite plugging of inorganic scale deposition,microbial biofilms and organic substances in water injectors in ultra-low permeability reservoirs in northern Shaanxi,this study innovatively proposes a mild sequential composite plugging removal technology.Through multi-scale characterization such as XRD,FTIR,and SEM-EDS,the plugging material is identified as an organic-inorganic composite structure with a ratio of 1∶9,among which the polysaccharide-protein network of SRB(Sulfate-Reducing Bacteria)biofilms wraps around inorganic scales to form a dense barrier,resulting in the failure of conventional plugging removers.Based on this,a three-stage synergistic plugging removal system is constructed and its graded plugging removal mechanism is clarified.The first stage is biofilm breakdown:0.03%quaternary ammonium salt bactericide JY-1 and 0.4%-0.5%biofilm stripper(mass ratio of amylase to protease is 1∶1)is engaged,which breaks the physical barrier of biofilms through the enzymatic degradation of polysaccharide skeletons and protein matrices.The second stage is inorganic scale dissolution:3.0%EDTMP chelating agent,3%HCl,and 0.8%sodium citrate is engaged,which selectively dissolves CaCO3/FeS and inhibits secondary precipitation.The third stage is flowback assistance and formation damage prevention:0.4%fluorocarbon surfactant FT-1,1%isopropanol,and 0.5%imidazoline corrosion inhibitor ML-1 is engaged,which promotes the flowback of residues by reducing interfacial tension force,while the imidazoline forms an adsorption film on the pipe walls to inhibit corrosion.Laboratory-scale experiments show that this system achieves a dissolution rate of 92.3%,a corrosion rate of 0.047 mm/a,and both the anti-swelling rate and iron removal rate exceed 84%.This system is significantly superior to the traditional mud acid(45.2%)and chelating acid(65.1%)systems in terms of dissolution rate.In field tests,the water injection pressure decreased from 15 MPa to 2.0 MPa,with an effective period of more than 6 months.This technology solves the plugging challenges of water injectors in this oil area and provides an efficient and low-damage approach for the treatment of composite plugging in ultra-low permeability oilfields.