Analysis of sudden change of viscosity of drilling fluid by drilling method in cretaceous jurassic strata
In the process of drilling in Kekegai Coal Mine in the western China,the viscosity of drilling fluid increases suddenly,which seriously affects the drilling speed.The viscosity of drilling fluid sud-denly increases when crossing the cretaceous jurassic strata,which seriously affects the drilling speed.Therefore,the reasons for the sudden change of drilling fluid viscosity were investigated by experi-mental method.Additives such as sodium tripolyphosphate,sodium carboxymethyl cellulose and rock powder at different layers were added in the experiment,and the change of drilling fluid viscosity was observed.Comparative experimental analysis showed that sodium tripolyphosphate decreased the vis-cosity of drilling fluid,while sodium carboxymethyl cellulose increased the viscosity.The additions of 293 m and 391 m layers sandstone powder had little effect on the viscosity of drilling fluid,and the funnel viscosity was always maintained at about 27 s.However,adding mudstone powders at 276 m and 402 m layers could increase the viscosity of drilling fluid.Through XPS semi-quantitative analysis of the corresponding samples and XRF semi-quantitative analysis and SEM SEM analysis of the corre-sponding drilling fluid,it was found that the cretaceous jurassic mudstone contained relatively high concentration of magnesium,and the Mg2+concentration would increase when the drilling method was carried out in this strata.With the increase of Mg2+concentration,the high concentration of Mg2+pro-moted the exchange of cation between the layers of montmorillonite and entered its spatial structure,thus increasing the flocculation degree of montmorillonite and resulting in the increase of the overall viscosity of drilling fluid.
万方数据
维普
