Study and Application of a Gelled Foam Treatment Technology for Water Shutoff in Naturally Fractured Reservoir

The paper demonstrates a water shutoff technology in naturally fractured reservoir, which is based on simultaneous placement of a polymer gel and foam in fracture, where foam is stabilized by delayed formed gel. Lab studies were undertaken to develop a gelled foam formulation. A series of fracture blocking tests were performed to evaluate water-blocking capacity of gelled foam in fractured models. The optimized gelled foam has stronger water-blocking capability and greater residual resistant factor than regular gel. The influence of residual oil in fracture to gelled foam is also studied; a pre-treating fluid is used to enhance blockage effectiveness. The field trial design and execution of gelled foam treatment on an oil well in fractured reservoir are described. The results show that water cut decreases from 90% to around 40%, the oil production rate has been drastically increasing for more than 18 months, indicating longer effective lifetime of gelled foam treatment when compared with other water shutoff trials in this kind of reservoirs