High flexibility of prefabricated pumping stations in collecting and transporting storm water has been recognized. Nevertheless, flows inside such a complex system have rarely been reported. The present study aims to reveal water-sand flow characteristics in a prefabricated pumping station and to optimize geometric parameters of the tank to mitigate sand particle deposition. Five tank schemes, varying in the ratio of the diameter to the height of the tank bottom (D/L), were investigated. Flows in the pumping station were simulated using the computational fluid dynamics (CFD) technique. Test data were used to validate the numerical scheme. Three-dimensional water-sand flows in the pumping station were described. Underlying mechanisms of sand particle deposition were explained. The results indicate that the risk of deposition is high at the tank bottom side, close to the tank inlet. Both the tank bottom geometry and the inlet suction of the pump contribute to sand particle deposition. The averaged sand volume fraction at the pump inlet reaches its minimum at D/L = 3. Sand particle velocity at the pump inlet varies inversely with D/L. The highest intensity of the vortex at the pump inlet arises at D/L = 3. The best anti-deposition performance of the pumping station is attained at D/L = 3.

No abstract

No abstract

For extra-low permeability reservoirs, with a permeability of about 0.3×10 -3 μm 2 , fl uid fl ow and production performance in cores were studied. A long core holder with a multi-location piezometric measurement was specially designed. An artifi cial long core, about 700 mm long and with a cross section of 45mm×45mm, was used. In the experiment, pressure distribution along the core can be measured in real time. Single phase fl ow in the core was investigated. Different modes of production in long cores were also simulated including natural depletion, water fl ooding, and advanced water fl ooding. Through physical simulation, fl ow parameters were collected and production characteristics in extra-low permeability cores were studied. From experimental results, it can be seen that fl uid fl ow in extra-low permeability cores is different from that in high permeability cores. Transmission of pressure in extra-low permeability cores is very slow, and it needs a long time for the pressure to become stable. The distribution curve of pressure along the core is nonlinear and the production rate in extra-low permeability reservoirs decreases sharply. The development effects of different production modes in extra-low permeability cores were compared with one another. Among the production modes, advanced water fl ooding has much potential for effective development of extra-low permeability reservoirs. Natural depletion and conventional water fl ooding can also be used in early production periods. In addition, the countermeasures and some ideas especially for the potential development of extra-low permeability reservoirs are suggested.