欠饱和复合盐硅酸盐钻井液KSN配方研究

欠饱和盐水钻井液具有较强的抗盐能力和抑制性能,而硅酸盐钻井液具有费用低、抑制性强、保护环境等优点,因此考虑用欠饱和复合盐硅酸盐体系解决盐膏层的井壁不稳定问题.通过室内实验,研制出了一种防塌能力强的欠饱和复合盐硅酸盐钻井液(KSN)体系.该体系稳定盐膏层井壁机理为:Na2SiO3/GXL-1协同封固井壁,阻缓压力传递及滤液传递;KCl/Na2SiO3协同抑制石膏溶解;KCl/Na2SiO3/NaCl协同抑制地层水化,防塌作用效果显著.评价了该体系的抗石膏和抗劣土污染性能、阻缓压力传递和滤液传递能力、抑制石膏溶解能力、抑制水化以及稳定井壁效果.实验结果表明,所研制的KSN体系具有优异的护壁防塌能力和滤失造壁性能,动塑比高,携带能力强.

Study on compound undersaturated brine silicate drilling fluid(KSN)

Undersaturated brine drilling fluid has strong inhibition and salt resistance,and silicate drilling fluid has some advantages such as low cost,strong inhibition and environmental protection.So the undersaturated compound brine silicate drilling fluid was considered to prevent wellbore instability of the gypsum bed.On the basis of lab experiments,a undersaturated compound silicate drilling fluid system(KSN) with strong anti-sloughing ability was developed.The mechanism of KSN drilling fluid stabilizing wellbore of the gypsum bed are as followed: plugging wall by synergetic effect between Na_2SiO_3 and GXL-1,preventing pressure and filtrate transmission;preventing gypsum from dissolving by synergetic effect between KCl and Na_2SiO_3;inhibiting formation hydrating by synergetic effect of KCl/Na_2SiO_3/NaCl.The effects of gypsum resistance,preventing/delaying transmission of pressure and filtrate,inhibiting the gypsum dissolving and formation hydration and stabilizing the borehole were evaluated.The experimental data indicated that KSN drilling fluid had excellent properties of wellbore stability controlling,filtration cake building and cuttings carring,and had a higher ratio of YP to PV.