用于钻井堵漏和封堵的特种凝胶抗冲稀性能

Anti-dilution properties of a special gel applied to loss circulation control in drilling

特种凝胶ZND在国内30多口井/次恶性漏失和负安全密度窗口的高压双庙1井、高含H2S的罗家2井、高含CO2的徐深8—平1井喷漏同存的成功处理中彰显出了重要作用,强大的抗冲稀能力是其发挥作用的关键因素。研究了特种凝胶ZND的溶解热和稀释热,选用筛余体积变化率直观地表征它的抗剪切冲稀能力,借助大尺寸堵漏模拟装置模拟了它在破碎性地层漏层中的抗冲稀能力。结果表明,特种凝胶ZND稀释热越小,其抗冲稀能力越强;抗冲稀能力随温度升高、浓度降低、剪切速率增大和剪切时间延长而减小;等孔隙体积水驱替特种凝胶时,凝胶被驱替率均小于16%,当出口见水后,采用2倍孔隙体积的水驱替凝胶ZND时,被驱出的凝胶体积率均小于2%。实验验证了特种凝胶ZND具有强的抗冲稀能力,为有效堵住恶性漏失和对付喷漏同层的安全隐患提供了科学的实验依据与理论指导。

The special gel-ZND has been successfully applied to dealing with severe loss circulation problems in more than thirty wells/ times in China, especially for the negative safe-mud-density windows and higb-pressure Shuangmiao 1 Well, the high H2 S Luojia-2 Well and the high-CO2 Xushen-8-Ping-1 Well, where blowout and loss circulation co-occurred and this special gel played an important role in their accident treatment. One of the key factors for the gel to successfully control loss circulation is its strong anti-dilution property. The present paper studied the solution heat and dilution heat of the special gel-ZND in terms of thermodynamics, and as- sisted with a large-scale plugging simulation device, the volume change rate of screen residue was chosen to intuitively characterize the anti-dilution property of the gel in the loss zone of fragmented formations. The experimental result showed that the lower the di lution heat of the gel-ZND is, the stronger the anti-dilution ability of the gel is. This anti-dilution ability decreases with increasing tem- perature, reducing the concentration of the gel, enhancing shear rate and prolonging shear time. When the special geI-ZND with a concentra- tion above 1. 0% was displaced by equivalent-pore volume water, the displaced rate was all lower than 16%, while all the volume rate of the displaced gel was lower than 2% when the two-times-pore volume water was employed to displace the gel-ZND after water breakthrough oc- curred in outlet. The experiment proved that the special gel-ZND has a strong anti-dilution ability, and the results have provided the experi- mental basis and theoretical guidance for eliminating potential safety hazards caused hy severe loss circulation or the blowout-loss circulation in the same formation.