| Managed pressure drilling (MPD) is an advanced technique to improve drilling safety as well as greatly reduce the cost. MPD throttle valve is a key component to achieve pressure control technology, which is in direct contact with the drilling fluid to control wellbore pressure. Its performance directly affects the success rate of MPD process implementation. So a kind of durable and reliable throttle valve is a defined guarantee for successful implementation of the MPD technology. Recent years, scholars have studied many aspects of throttle valve and made tremendous achievements, such as pressure control capacity and material selection. However, few literature and research reports have been found about extending the life of domestic MPD throttle valve. The short service of throttle valve has become the most prominent bottleneck. This paper treats the flow field of valve housing as breakthrough to optimize the design of the throttle valve. The main results are as follows:1. The significance of throttle valve performance to MPD technology has been analyzed; the most prominent drawback, anti-erosion characteristic, between domestic and imported throttle vale has been indicated. The research process of erosion study has been reviewed. At last, a research method to mitigate throttle valve erosion based on optimization of valve housing is decided.2. The current study results of a new cylindrical MPD throttle valve have been summarized. The performance experiment between the new valve and T3 valve has been carried out. The results show that the new cylindrical MPD throttle valve has an advantage in the pressure control range as well as control stability.3. Existing erosion prediction model has been investigated intensively, the erosion experiment of the new kind throttle valve under the circumstance of particle volume concentration 2.47% has been carried out, and the results have been compared to erosion prediction on the aspect of erosion mass loss and erosion distribution law. The compare shows: the predicted erosion loss with 5 hours has a high consistency with experimental data; the predicted erosion area and profile is precise. It provides the selection of DPM and related model is correct, such as force model, collision reflection function, drag force model and erosion model.4. The table unit erosion experiment was taken to study the erosion mass loss and distribution laws versus time and erosion degree when the particle volume fraction is 17%. Dense Discrete Particle Model was elected to predict erosion. The results show the prediction of erosion profile and trends of mass loss is accurate. It verified the validity of the DDPM.5. Combining FLUENT and Design Explorer,50 groups experiments was designed, Kriging response surface was calculated. Aiming to the minimum of plug mass loss, the relationship versus parameters of throttle valve housing was studied, the laws was found and the best size was confirmed.6. Comparing the mass loss of plug and erosion rate on the contour in symmetrical plane before and after the optimization, we get that not only the average erosion mass loss of the plug was decreased, the local erosion condition also improved.After the research of this paper, the reliable experimental data for throttle valve erosion prediction was got, the relationship between plug erosion mass loss and chamber parameters were cleared, and the best size was determined. After the optimization the service life of the new throttle valve was extended. This paper also validated DDPM and Design Explorer and provided a feasible and accurate prediction models; the extension of service life of the new cylindrical throttle valve has important significance to break the monopoly of the foreign products. the improvement of the new throttle valve will also provide tools support for the promotion of domestic MPD system; it will have a certain role to help oil companies reduce cost and go through the period of low oil prices. |
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