Deepwater low-density ternary solid phase cement slurry system based on close packing theory
In the process of cementing in deepwater shallow formations,the low temperature at the sea floor results in slow development of the early mechanical strength of the cement sheath and low internal compactness of the cement sheath,which leads to water and gas channeling,causing poor cementing quality and even seal failure and other complex accidents.In this paper,the fractal characteristics equation is used for the close packing of G-grade oil-well cement,nano CaCO3(NC)and cenospheres(CS).Then,a set of ternary solid-phase cement slurry system with a density of 1.50 g/cm3 and the properties of low temperature and early strength is selected through indoor experimental evaluation.Finally,the strengthening mechanisms of close packing system are characterized and analyzed by means of compressive strength test,XCT and SEM.And the following research results are obtained.First,the mechanical strength of the ternary close packing system develops rapidly in the early stage,and the compressive strength at 24 h can reach more than 3.5 MPa under 10℃.Second,compared with the NC binary system and the CS binary system with the same density,the ternary system is 19.10%-33.05%lower in porosity and 7.0%-21.1%higher in compressive strength.Third,NC can provide nucleation sites for cement hydration and fill and refine the pores,and CS can partially replace the water to improve the densification of the system.Under the synergistic effect of these two materials and the close packing effect,the early mechanical strength can develop rapidly.In conclusion,the ternary solid-phase cement slurry system gives full play to the advantages of three kinds of materials on the basis of close pacing theory,so as to realize the rapid development of early mechanical strength,which has certain theoretical significance and application value for preventing water and gas channeling during the cementing operation of surface casing in deepwater wells.
国家科技期刊平台
NSTL
万方数据
维普
