Throttle characteristics of multi-stage circumfluence nozzle during the separate-layer injection of CO_(2)

Separate-layer injection of CO2 is an important method to improve oil and gas production and recovery.Conventional single-stage nozzle is usually blocked by impurities,and the ice-barrier phenomenon is very common.To solve this problem,large-diameter multi-stage circumfluence nozzle was designed to release pressure stage by stage.In order to illuminate the throttle characteristics of the CO2 multi-stage circumfluence nozzles,numerical simulation was performed to test several nozzles with different diameters and stage numbers.Furthermore,we tested the throttle characteristics through laboratory experiments and obtained the effects of several critical parameters such as nozzle diameter,number of stage and pressure drop on the throttle characteristics.The results show that the flow rate decreases as the nozzle stage increases on the condition of constant pressure and nozzle diameter.And pressure difference increases as nozzle stage number increases under the constant flow rate.The throttle capability of multi-stage circumfluence nozzles was much better than the concentric nozzles.Large-diameter multi-stage nozzle is recommended rather than small-diameter single-stage nozzle during the process of separate-layer injection,which can efficiently prevent impurities and ice blocking.The results are expected to provide a theoretical support for the nozzle choice of separate-layer injection of CO2.

Preparation and properties of physically and chemically cross-linked hybrid hydrophobic association hydrogels with good mechanical strength

To correct the defects of hydrophobic association hydrogels （HA-gels）, new physically and chemically cross-linked hybrid hy- drophobic association hydrogels （hybrid HA-gels） were prepared by radical copolymerization of acrylamide （AM）, octylphe- nol polyoxyethylene （n） acrylate （OPnAC, n stands for the number of ethoxy group, and is 10 and 21） and N,N＇-methylene- bisacrylamide （MBA）. On the basis of the statistical molecular theory of rubber elastic, the Mooney-Rivlin model and using the tensile true stress （O＇true） tested at room temperature, the number of network strands per unit volume （o~） and the num- ber-average molar mass of a network strand （Me） were evaluated for hybrid HA-gels. For the hydrogels, the effect of the con- tent of MBA and OP10AC on their tensile mechanical properties was studied by using o0 and Mc; also, the effect of the com- positions and temperature on their swelling behavior in distilled water was discussed in detail. In addition, hybrid HA-gels in- cluding a small quantity of MBA possessed the capabilities of secondary self-healing and remolding. In contrast with HA-gels prepared by the same compositions besides MBA, hybrid HA-gels showed good mechanical strength and long-term thermal stability in distilled water in the range of 25 to 80℃. Furthemore, hybrid HA-gels also avoided the self-deswelling behavior of HA-gels. The results show that the application fields of HA-gels will be greatly broadened after introducing a chemical cross-linking network.