超高温高密度油基钻井液研究与性能评价

深层超深层油气钻探中面临着超高温高压、高压盐水、巨厚盐膏层和泥页岩层等复杂地质条件，导致油基钻井液的乳化稳定性、流变、滤失损耗等性能极难调控。合成了不饱和酸酐接枝妥尔油脂肪烃基的咪唑啉酰胺类主乳化剂和辅乳化剂，选用抗高温增黏剂、流型调节剂、润湿剂和降滤失剂，采用API重晶石和超细硫酸钡复合加重，构建了超高温高密度油基钻井液配方。性能评价结果表明，该超高温高密度油基钻井液抗温达220 ℃，复合加重后流变性显著改善，密度最高可达2.8 g/cm3，可抗40%淡水、40%复合盐水、5%～10%泥页岩岩屑和5%～10%石膏污染；在65 ℃/常压～220 ℃/172.5 MPa下具有良好的流变稳定性和悬浮稳定性。该超高温高密度油基钻井液为深层超深层油气资源的安全高效钻探提供了技术支撑。 

Study and Performance Evaluation of Ultra-High Temperature High Density Oil Based Drilling Fluids

Difficulties in controlling the emulsion stability, rheology and filtration property of the oil based drilling fluids are often encountered in drilling deep and ultra-deep wells in which high temperatures, high pressure formations and salt-waters, thick salt and gypsum zones and shale formations are penetrated. To deal with these problems, an ultra-high temperature high density oil based drilling fluid was formulated with synthesized emulsifiers, high temperature viscosifier, flow pattern additive, wetting agent, filter loss reducer and ultra-fine barite. The emulsifiers are an imidazoline amide with tall oil aliphatic hydrocarbon group grafted with unsaturated anhydride. Laboratory evaluation of the drilling fluid demonstrated that this drilling fluid can work normally at temperatures up to 220 ℃. The density of the drilling fluid can be weighted to 2.8 g/cm3. Using compounded weighting agents significantly improved the rheology of the drilling fluid. This drilling fluid is able to resist to contamination from 40% fresh water, or 40% compound salt water, or 5% – 10% shale cuttings, or 5% – 10% gypsum. The drilling fluid had good rheological stability and suspending stability at 65 ℃/atmospheric pressure to 220 ℃/172.5 MPa. This ultra-high temperature high density oil based drilling fluid has provided a technical support to the safe and efficient development of deep and ultra-deep buried oil and gas resources.