压裂用纳米体膨颗粒裂缝封堵性能实验研究

近年来，纳米颗粒用于提高采收率对小孔隙进行封堵的研究较多，但很少有人将其用于压裂工艺，对低渗透储层出水微裂缝进行封堵。因此通过调研优选出纳米体膨颗粒作为堵剂，将其用于裂缝封堵性能实验。利用自制岩心封堵实验装置，分析了纳米体膨颗粒对水流和油流裂缝通道的封堵能力，以及其自身的膨胀性、注入性和在水流裂缝通道中的耐冲刷性。实验结果表明，纳米体膨颗粒在水相环境中具有较强的吸水膨胀性能，在油相环境中具有弱膨胀性能；纳米体膨颗粒对水流裂缝的封堵效果良好，在围压为40和50 MPa下水相封堵率高达90%；对油流裂缝不会形成很强的封堵，油相封堵率小于30%。此外，纳米体膨颗粒的注入性能良好。在围压为40 MPa、注入3 PV浓度为2%的纳米体膨颗粒在水流裂缝中，膨胀4 d后的耐冲刷性良好；因此纳米体膨颗粒达到了封堵水流裂缝而不封堵油流裂缝的目的，能较好地应用于压裂堵水。 

Experimental Study on Fracture Plugging Performance of Volumetric Expansion Nano Particles Used in Well Fracturing

Nano particles as plugging agent used to shut off fractures with small sizes have been frequently studied in recent year, while their use in shutting off water-producing fractures in low-permeability reservoirs in fracturing operation is less studied. In this study nano particles were selected for fracture plugging experiment. Nano particles' ability to shut off fractures producing water and fractures producing oil was evaluated on a self-made core plugging experiment device. Nano particles' expandability, injectability and the resistance to washing in fractures with water flow were also studied. The experimental results showed that the volumetric expansion nano particles absorb water and expand greatly in water environment. In oil environment, the nano particles have very weak expandability. The nano particles can shut off fractures producing water very well. The amount of water shut off at confining pressure of 40 MPa and 50MPa can be as high as 90%. In shutting off fractures with oil flow, there is only 30% of the oil shut off. The nano particles have good injectability; at confining pressure of 40 MPa, 3 PV of fluid containing 2% nano particles were injected into fractures with water flow, and they stayed firmly inside the fractures after expanding for 4 d. These experimental data prove that the volumetric expansion nano particles will shut off water instead of oil, and can be used in well fracturing and water shutoff.