白垩侏罗系地层钻井法凿井钻井液黏度突变致因分析

Analysis of sudden change of viscosity of drilling fluid by drilling method in cretaceous jurassic strata

在西部地区可可盖煤矿钻井法凿井过程中,穿越白垩侏罗系地层时遇到钻井液黏度突然增大的问题,严重影响了钻进速度。为此,通过实验方法探究了钻井液黏度突变的原因。实验中添加了三聚磷酸钠、羧甲基纤维素钠等外加剂以及不同层位的岩粉,并观察了钻井液黏度的变化。对比实验分析发现,三聚磷酸钠降低了钻井液黏度,而羧甲基纤维素钠增加了其黏度。添加293、391m层位的砂岩岩粉对于钻井液黏度几乎没有影响,漏斗黏度始终保持在27s左右;然而,在添加276、402m层位泥岩岩粉后,可以使钻井液黏度增大。通过XPS半定量分析相应样品以及采用XRF半定量分析和SEM电镜分析相应的钻井液发现:白垩侏罗系泥岩含有较高浓度镁元素,在该地层进行钻井法凿井时会导致Mg^(2+)浓度上升;随着Mg^(2+)浓度增加,高浓度Mg^(2+)促使蒙脱石层间阳离子与之交换并进入其空间结构中,从而引起蒙脱石絮凝程度提高并导致整体钻井液黏性增大。

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 suddenly 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 experimental 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 viscosity 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 corresponding drilling fluid,it was found that the cretaceous jurassic mudstone contained relatively high concentration of magnesium,and the Mg^(2+)concentration would increase when the drilling method was carried out in this strata.With the increase of Mg^(2+)concentration,the high concentration of Mg^(2+)promoted 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.