School of Petroleum Engineering,Key Laboratory of Drilling and Production Engineering for Oil and Gas,Yangtze University
准噶尔盆地南缘山前钻遇地层含有大段膏泥岩且地层压力高，高密度油基钻井液因其本身优异的性能已成为该地区复杂层段首选钻井液体系，以0＃柴油和白油为基油的高密度油基钻井液优良的性能保证了复杂层段钻井的顺利进行。但由于准噶尔盆地南缘地区秋冬季部分钻井时段地面环境温度较低，甚至低到-40℃，而0＃柴油和5＃白油的凝固点为-4℃和10℃，较高的凝固点给油基钻井液在低温环境下的配制及性能的稳定性带来较大的影响。在0＃柴油基油基钻井液配方的基础上，采用低凝固点（-38℃）的-35＃柴油为基油，通过调整体系的乳化剂，润湿剂及有机土等材料的组成，适量增加提切剂，构建出适应低温环境的高密度油基钻井液体系：-35＃柴油+ 3.2%主乳HIEMUL-1+ 0.4%辅乳HZCOMAT-2 + 4%润湿剂HZCOT+0.8%有机土HFGEL-120 + 3%降滤失FC-TROL150+0.2%提切剂（HSV-4)+ 1.5% 氧化钙+1%成膜剂 +重晶石（加重2.50g/cm3，油水比95:5，水为：25% CaCl2溶液）。钻井液体系性能研究结果表明：基于低凝固点柴油高密度油基钻井液体系综合性能优良，不仅能满足-10℃条件下的配制及性能要求，而且在高温180℃、密度2.5g/cm3的地层条件下，钻井液流变性优良，乳化性能稳定（1000V以上）且抗污染性能强（抗钙15%、抗盐10%、抗水20%）；同时具有良好的封堵（封堵承压为7.75MPa）性能和防漏（模拟裂宽为0.5mm，防漏承压为7.0MPa）性能。
The formation in the southern margin of the Junggar Basin contains large sections of mudstone with high pressure. The high-density oil-based drilling fluid has become the preferred drilling fluid for complex formation due to its excellent performance. The high density oil-based drilling fluid based on 0# diesel oil and mineral white oil ensures the smooth well-drilling because of its excellent performance. The surface temperature in the southern margin of junggar basin is very low in winter, even as low as -10℃, while the freezing point of 0# diesel oil and mineral white oil is -4℃and 10℃. This study adopts the low freezing point (-38℃)-35 # diesel oil as base oil, by adjusting the drilling fluid of emulsifier, wetting agent, and the composition of the organic material such as soil, appropriately increased cutting agent content, and then constructs high density low freezing point to adapt to the low temperature environment oil-base drilling fluid. The oil-based drilling fluid with low freezing point is developed on the basis of the widely used 0# diesel-based drilling fluid formula in the field. The formula is composed of: -35#diesel + water (25% CaCl2 solution) +3.2% HIEMUL-1(main emulsifier)+ 0.4% HZCOMAT-2 (auxiliary emulsifier)+4% HZCOT (wetting agent)+0.8%HFGEL-120(organic soil) +3%FC-TROL150(filtrate reducer) +0.2%HSV-4(viscosifier)+1.5%calcium oxide +1%FD-1(film forming agent ) +barite. It should be noted that the oil-water volume ratio in the drilling fluid formula is 95: 5, and the addition amount of other additives is relative to the total mass content of oil and water, and the density is 2.5g/cm3. The performance research results show that oil-based drilling fluid with the high-density and low-freezing point has excellent comprehensive performance, and can meet the formulation and performance requirements at-10° C. For example, under the conditions of temperature 180℃and density 2.5g/ cm3, the drilling fluid has excellent rheology, stable emulsification performance (above 1000V) and strong anti-pollution performance (anti-calcium 15%, anti-salt 10%, anti-water 20%); Blocking capacity (blocking bearing pressure is 7.75MPa, leak proof bearing pressure is 7.0MPa).