泡沫注入方式对封堵效果的影响

Effects of Foam Injection Methods on Plugging Efficiency

比较了气液同时注入、多段塞气液交替注入、气-液-气、气-液-气(含油)、气-液-气(无发泡剂)及液-气-液注入方式对阻力因子、突破压力和封堵率的影响。结果表明,气-液-气注入方式中气体前置段塞隔离了油水层,使发泡剂性能稳定,后置气体段塞驱替泡沫进入地层深部,扩大波及体积,提高泡沫质量,突破压力最大,达1.033 MPa,封堵率也最高,是最好的注入方式;多段塞气液交替注入方式可以把气体和发泡剂驱替进入地层深部,扩大泡沫波及范围,发泡剂在岩芯中吸附提高了泡沫的稳定性,但注入工序多;同时注入方式在实验室和现场都很难达到设计气液比,注入压力梯度小时没有起到封堵作用,注入压力梯度大时注入困难;液-气-液注入方式的前置段塞损失很大,后续注入的发泡剂溶液降低了泡沫质量,破坏了泡沫的稳定性和封堵能力;不加发泡剂的气-液-气注入方式形成的泡沫液膜粘度低,封堵能力较低。考察了泡沫体系中含油量对封堵效果的影响,结果表明,油的存在只是增加了油层流出速度,对封堵效率没有明显影响。

The effects of different injection methods including gas - liquid simultaneous injection, sectional alternating injection, gas - liquid - gas injection, gas - liquid - gas injection （ containing oil）, gas - liquid - gas injection（no foaming agent）, and gas- liquid- gas injection,on the resistance coefficient, breakthrough pressure and plugging efficiency were compared. The result showed that for gas - liquid - gas, pregas slug isolated oil and water zones, made foam stable, subsequent gas slug displaced foam into deep formation, amplified swept volume, raised foam quality, breakthrough pressure was the largest at 1. 033 MPa, plugging efficiency was also the highest, so it was the best injection method. Sectional alternating injection method could displace gas and foam agents to deep formation, broadened swept volume. Adsorbing of foam agents in cores improved the foam stability, but the method had more operations. Simultaneous injection method was difficult to gain the designed gas/liquid ratio in laboratory and field. When injection pressure gradient was high, it was difficult to inject, otherwise no plugging effect. Preliquid slug of liquid - gas - liquid lost greatly, sequent injected foam agents decreased the foam quality and damaged the foam stability and plugging intensity. The liquid film viscosity of gas -liquid -gas disperse system（no foaming agent） was low, plugging intensity was also low. The effects of oil content in foam system on the plugging were examined. The result showed that the presence of oil only increases outflow velocity, not obviously affected plugging efficiency.