一种耐高温密度可调的柔性胶粒新型完井液

A novel high-temperature-resistant, variable-density,flexible colloidal particle completion fluid

中国含油气盆地普遍存在高温高压多压力系统油气藏,高温高压多压力系统油气藏给完井工程带来巨大挑战。为了解决多压力系统油气井完井过程中“漏喷同存”与储层损害的难题,研发了一种耐180℃高温且密度可调的柔性胶粒完井液体系,通过物理模拟和核磁共振实验研究了柔性胶粒承压性能和返排机理,基于流变实验测试了柔性胶粒体系的黏弹性,利用红外光谱实验明确了柔性胶粒体系耐高温机理。研究结果表明:①对于不同渗透率(40~2337 mD)岩心,在15~19 MPa的正压差下,柔性胶粒暂堵后岩心无滤失,渗透率恢复率介于85%~94%;②核磁共振(NMR)实验证实了大分子柔性胶粒在小孔喉中的滞留是岩心渗透率降低的主要原因;③流变测试表明了柔性胶粒体系为黏弹性体(即G'>G",G'表示弹性模量,G"表示黏性模量),以弹性为主;④红外光谱实验显示磷酸盐盐水与柔性胶粒之间存在氢键是完井液体系耐高温的主要原因;⑤柔性胶粒完井液成功应用于海上某地层“压力反转”井完井作业,现场验证承压达16.5 MPa,射孔期间基本无工作液漏失,作业完成后平均瞬时产气量达3940 m3/h。结论认为,柔性胶粒完井液可为多压力系统油气藏的安全高效完井作业提供技术支撑,为深层、低渗透油气藏的安全高效钻采提供了新思路和新技术。

Petroliferous basins in China commonly contain high-temperature and high-pressure(HTHP) reservoirs under a multi-pressure system, which brings great challenges to well completion engineering. In view of the problems of coexistence of lost circulation and blowout and reservoir damage during completion of oil and gas wells under a multi-pressure system, a high-temperature-resistant(up to 180 ℃), variable-density, anti-salt solidified water completion fluid system is developed. The pressure-bearing performance and flowback mechanism of flexible colloidal particles are studied by physical simulation and nuclear magnetic resonance(NMR) experiments, the viscoelasticity of the flexible colloidal particle system is tested through rheological experiments, and the high-temperature-resistant mechanism of the flexible colloidal particle system is determined by infrared spectroscopy experiments. The results show that the cores with different permeabilities(40–2 337 mD) display no lost circulation and a permeability recovery rate of 85%–94% after plugging with flexible colloidal particles under the positive pressure difference of 15–19 MPa. NMR experiments confirm that the retention of macromolecular flexible colloidal particles in small pore throats is the main reason for the decrease of core permeability. Rheological experiments reveal that the flexible colloidal particle system is a viscoelastic(mainly elastic) fluid(G′>G′′, where G′ represents the elastic modulus, and G′′ represents the viscous modulus). Infrared spectroscopy experiments demonstrate that the hydrogen bond between phosphate brine and flexible colloidal particles is the main contributor to the high-temperature resistance of the system. The flexible colloidal particle completion fluid system was successfully applied to the completion of an offshore well under reversal pressure in a formation, indicating that the pressure-bearing capacity is 16.5 MPa, almost no working fluid was lost during perforation, and the average instantaneous gas production is 3 940 m~3/h after perforation. It is concluded that the proposed flexible colloidal particle completion fluid provides a technical support for safe and efficient well completion in reservoirs under a multi-pressure system and also a new idea and technique for safe and efficient drilling and production of deep and low-permeability reservoirs.