脉冲推挤膨润土水泥浆封堵流动水恶性漏失层

油气井在钻井过程中容易出现地层漏失，尤其是含有流动地层水地层的漏失问题，存在漏速高、漏失量大，常用堵漏方法效果差、成功率低的问题。针对含流动水地层恶性漏失的封堵难题，研制了膨润土水泥浆体系，通过增加堵漏水泥浆中膨润土的含量，来提高堵漏水泥浆的黏度，提升其抗冲稀性。对膨润土水泥浆流变性、抗压强度和流动性能进行考察。结果表明，在保证抗压强度满足现场要求的前提下，建议膨润土加量为2.0%～2.5%，膨润土堵漏水泥浆体系在初凝前静止10 min后流动度明显降低，处于高稠状态。针对膨润土堵漏水泥浆的性能，设计了脉冲间隔推挤水泥浆堵漏工艺，通过调控推挤排量和间隔时间，使高稠态膨润土水泥浆被推挤入漏层，接近初凝时间时推挤水泥浆到位，该工艺能够使膨润土水泥浆滞留于漏失通道并凝固，提高堵漏成功率。华北某井现场应用结果表明，使用膨润土水泥浆配合脉冲间隔推挤工艺，可一次性解决含流动水恶性漏层的封堵难题，该技术现场施工简单，成功率高，成本低。 

The Technology of Interval Push Clay-Cement Slurry to Lost Circulation in Water Bearing Formation

Drilling into formations containing flow water is always accompanied with severe mud losses, and conventional mud loss control methods are seldom succeeded in controlling this kind of mud losses. To control this kind of mud losses, a bentonite cement slurry lost circulation material (LCM) was developed. By increasing the content of the bentonite in the mixture slurry, the viscosity of the slurry can be increased, thereby improving the ability of the LCM to resist thinning by the flowing water. Research on the rheology, compressive strength and flow property of the bentonite cement slurry has shown that the optimum bentonite concentration in the mixture is 2% – 2.5% provided that the compressive strength of the slurry has met the operational requirements. The mobility of the bentonite cement slurry is apparently reduced after standing for 10 min before initial gelling, at this time it is in high viscosity state. Based on the property of the bentonite cement slurry, a pulse squeeze method is designed for field operation. By adjusting the flow rate of squeezing the slurry and the time interval between two squeezes, the high viscosity bentonite cement slurry is squeezed into the loss channels. If the slurry at its initial gelling time is pushed into the loss channels, it will stay there and become cementing, in this way a high success rate of operation can be achieved. Application of this technique in a field operation in Huabei Oilfield has shown that the bentonite cement slurry, combined with the pulse squeeze technique, is able to control severe mud losses into formations with flowing water successfully at the first try. This low-cost technique is easy to operate and has high success rate in field application.