No abstract

The oscillating onset of the Rayleigh-Bénard convection (RBC) with viscoelastic fluids in a slightly tilted 2-dimension (2D) rectangular cavity with aspect ratio Γ = 2 was investigated for the first time via direct numerical simulation. A series of simulations were conducted in the plane of the Rayleigh number (Ra) and the tilt angle (α ∈ [0◦,5◦]) with three Weissenberg numbers (Wi = (0.1,0.15,0.2)) at a fixed Prandtl number Pr = 7.0. The evolutionary path of the oscillating convection onset in the (Wi,α)-plane was determined and corresponding complex flow structures were observed. The inclination of the box delays the onset of the oscillations and the corresponding Rayleigh number Rac as compared to the horizontal configuration. Oscillating flow structures acquire the attributes of a traveling wave. A specific feature of the oscillating convection in the case of the horizontal cavity, the periodicity in space and time exists in the inclined box case as well. But, the evolution of the oscillatory flow structure is very different from the horizontal case in that the counter-clockwise cell assimilates the clockwise cell.

No abstract

This paper describes the successful resin squeeze operation to seal off a micro-annulus between the 7" and 9-5/8" casings on a sour gas well located in Sichuan Basin, China. Integrated plug and abandonment were also essential to eliminate the risk of potential H2S exposure presented to the residents around this area. Resin, as a new alternative sealing technology, was technically evaluated, laboratory tested, and then chosen for squeezing into a micro-annulus to stop gas migration for its solids-free and low-viscosity properties compared to a conventional cement. The squeeze job was designed by taking the casing yield strength as the pressure limit (Confirmed by caliper log the casing was in good condition) and determining the resin pumping volume based on estimated resin squeeze volume and the remaining resin plug length. A "Braden-head" squeeze method was selected considering the low injection rate observed during the water injection test. Both stage-up and stage down squeezing techniques (hesitation squeeze of increasing and decreasing wellhead pressure stage by stage) were performed to maximize the injected volume of the resin sealant. A total of 800 L of 9.16 lb/gal resin was placed into a 4 ft milled interval, and 50 L were successfully squeezed into the 7" × 9-5/8" casing annulus. An operational learning was that resin injection is greatly improved during the stage-down process while keeping the casing annulus open. Evidence that the micro-annulus leak path had been sealed was an observation of 0 psi on the 7" × 9-5/8" casing annulus after resin fully set. The method of locating the optimal spot to squeeze resin involved noise logging to analyze for a potential gas source in the annulus. The post job results confirmed that resin acts effectively as an annular barrier in the repair of gas leaks in the small volume situations where micro-annulus exists in the cement sheath. For large voids such as inside 7" casing, a combination of cement plug plus mechanical barrier is recommended to be placed directly above resin plugs to complete permanent plug and abandonment of the wellbore.

The radial temperature difference calculation of a steam drum shell is an important step in the process of calcu-lating its heat stress, so the current Chinese Standard recommended a computing method which was derived from the further modification to the simplified solution for the radial temperature of a steam drum shell. In order to derive the feasibility for the application of the current Chinese Standard computing method to a supercharged boiler, the computing method for the temperature difference of a steam drum shell, which was based on the approximate solution for the radial temperature of a steam drum shell and highly approaches to its analytic solution, was exercised. By analysing the computed results of examples, the conclusions show as follows: The current Chinese Standard computing method for the radial temperature difference of a steam drum shell can’t meet the calculation requirements of all the running work conditions and their courses of a supercharged boiler, and as a universal computing method, it can’t serve as a computing method for the same problem of a supercharged boiler. Whereas the approximate solution can apply to calculating the same problem of a supercharged boiler and a peak shaving utility boiler. Thereby the basis is offered for the selection and usage of the computing method for the radial temperature difference of a supercharged boiler steam drum shell, the pioneering researches on its interrelated problems and prac-tical applications.