Research And Application Of Cement Slurry System Based On Compound Expansive Agent

The volume shrinkage of oil well cement hydration will lead to serious problems such as poor cement joint quality and induced annulus turbulence.It may also be an important factor leading to safety accidents in underground and wellsites.Therefore,it is necessary to avoid the volume shrinkage of the cement ring to completely solve the problem of annulus turbulence and cementation quality.This paper begins with the expansion mechanism of several existing expansion agents baseon the shrinkage problem of cement hydration.According to the limitation of the oil well cement ring in the narrow space,the space limited expansion mechanism is preferred as the principle basis for developing the expansion agent.Then,the advantages and disadvantages of each of the three existing expansion agents SW＿G,SW＿P,and SW＿E are analyzed.According to the synergistic mechanism,the three expansion agents were compounded at 2:0.3:0.3 to obtain the expansion agent GPE.The expansion agent can effectively solve the problem of volume shrinkage when cement is hydrated.The evaluation results show that the expansion agent can significantly improve the interface cementation strength,reduce the porosity and permeability of the cement stone,improve the pore throat radius distribution,and have less impact on other properties of the cement slurry.At the same time,based on the composite expansion agent GPE,an expanded cement slurry system was developed(victory G-grade cement + 0.4% JS-3 + 3.0% GPE + 1.1% SXY-2+0.3-1.0% HN-2 + tap water).The system has good expansion ability and anti-gas smashing ability,and can significantly improve the interface cementation strength of cement stone;it has the characteristics of low water loss,stable no free liquid,easy adjustment of thickening time and good rheology.The pore size of the cement slurry was found to be dense by the pore size analysis,microscopic analysis and permeability measurement of the cement specimen.The cement slurry system was tested in the(37)177.8 mm tail pipe cementing of wells X 101 and X 202 in a basin.The results of electrical sound amplitude measurement and variable density detection showed that there was no annulus turbulence,and the first and second interfaces of the target layer were well sealed.