微米级石墨粉增强堵水凝胶性能实验研究

Experimental Study on Enhanced Performance of Hydrogel forWater Plugging by Using Micron Graphite Powder

能否封堵裂缝水窜通道是裂缝性低渗透油田实现高效注水开发的关键。封堵裂缝水窜通道需要高强度的凝胶堵剂,但是传统的丙烯酰胺类凝胶的强度偏低。针对此问题,文章通过添加成本低廉的微米级石墨粉以大幅度提升丙烯酰胺类凝胶的强度及综合性能。对比单一的丙烯酰胺凝胶体系,添加0.3%的微米级石墨粉后,弹性模量从120 Pa增加至400 Pa、黏性模量从48.6 Pa增加至268 Pa(1 Hz条件),相变温度由167℃增加至212℃,突破压力梯度由255 kPa/m增加至440 kPa/m(0.13 mm裂缝),断裂伸长率由700%增加至1100%,拉伸应力由38 kPa增加至110 kPa。可视化裂缝封堵实验对比显示,添加了石墨粉之后,再次注水所形成的网状水流通道特征明显,注入水突破压力高,封堵效果更有意义。石墨粉片层上的羟基、羧基参与了凝胶合成的物理化学反应,并且刚性结构的石墨粉可以支撑聚丙烯酰胺分子链的柔性骨架,从而大幅度提升了凝胶综合性能。实验结果尝试为裂缝性高含水油田的堵水作业提供出一种性能优异的新凝胶材料。

The key to achieve high efficiency development of fractured low permeability oilfield by using water injection is that the water channeling channel of fractures can be plugged.Due to the strong flow ability of water in the fracture,the gel-plugging agent with a high strength is required to plug the fracture.However,the strength of the traditional acrylamide gel is low.In view of the low strength of acrylamide gels to plug the fractured water channels,micron graphite powder with a low cost is added to enhance the strength and the comprehensive performance of acrylamide gel.Compared with a single acrylamide gel system,when 0.3%micron graphite powder is added,its elastic modulus is increased from 120 Pa to 400 Pa(at 1 Hz),its viscosity modulus is increased from 48.6 Pa to 268 Pa(at 1 Hz),its phase transition temperature is increased from 167℃to 212℃,its breakthrough pressure gradient is increased from 255 kPa/m to 440 kPa/m(for 0.13 mm fracture),its elongation at break is increased from 700%to 1100%,and its tensile stress is increased from 38 kPa to 110 kPa.Comparision of visual fracture sealing experiments shows that,after adding graphite powder to the polyacrylamide gel,the characteristics of the network-shaped water flow channel is more obvious and the breakthrough pressure of injection water is higher,which leads to a better plugging effect.The hydroxyl and carboxyl groups of the graphene powder sheet can interact physically and chemically with the amide groups of the polyacrylamide molecular chain.The graphite powder with a rigid structure can support the original flexible framework of polyacrylamide molecular chain.The synergistic effect of the rigid structure and the flexible structure can greatly improve the overall performance of the acrylamide gel.The experimental result is tried to develop a new gel material for water plugging operations of the fractured high water-cut oil fields.