页岩抑制剂与固井水泥浆接触污染机理及抗污染策略OA

To solve the contact contamination between a cement slurry and a drilling fluid,drilling fluid additives that impose serious contamination to the cement slurry are selected and studied to understand their mechanisms of contamination and to find ways of preventing the contamination.As one of the commonly used drilling fluid additives,shale inhibitor DFZ-7 has significant effects on the rheology of the cement slurry.The effects of DFZ-7 on the performance of the cement slurry and its contamination mechanism were investigated by means of fluidity test,compressive strength test,XRD,IR,TG and SEM etc.,and as a result of the investigation,an effective anticontamination strategy was developed.Experimental results show that at the early stage of cement hydration,the active groups in the DFZ-7 molecules can complex with the metallic cations on the surfaces of the cement particles to form network structures which hinder the movement of free water,causing the fluidity of the cement slurry to decrease and the viscosity thereof to increase.An anticontamination agent named KW was prepared by mixing aminotrimethylenephosphonic acid(ATMP)and titanium dioxide(TiO2)in a mass ratio of 5∶1.KW can be used to solve the contamination of DFZ-7 to the cement slurry through chelation and interstitial action.By adding 5%KW in the cement slurry,the fluidity of the cement slurry returned from 17.6 cm to 23.8 cm,and the strength of the set cement aging at 90℃for 1 d was increased from 1.56 MPa to 8.74 MPa.A mixture of the cement slurry and a drilling fluid(cement slurry∶drilling fluid=7∶3)had a thickening time of 55 min under the test conditions of 205℃×125 MPa×110 min.After treatment with KW(cement slurry∶drilling fluid∶spacer=7∶2∶1),the thickening time of the mixture was increased to 353 min,satisfying the needs of operation.In the set cement,the number of the network structures generated by DFZ-7 complexation decreased and the content of hydration products increased.The incorporation of KW can solve the contact contamination to the cement slurry by DFZ-7,without changing the composition of the hydration products of the cement slurry.